The corrosion behavior of 304L stainless steel(SS)in 3.5wt%NaCl solution after different cavitation erosion(CE)times was mainly evaluated using electrochemical noise and potentiostatic polarization techniques.It was f...The corrosion behavior of 304L stainless steel(SS)in 3.5wt%NaCl solution after different cavitation erosion(CE)times was mainly evaluated using electrochemical noise and potentiostatic polarization techniques.It was found that the antagonism effect resulting in the passivation and depassivation of 304L SS had significant distinctions at different CE periods.The passive behavior was predominant during the incubation period of CE where the metastable pitting initiated at the surface of 304L SS.Over the rising period of CE,the 304L SS experienced a transition from passivation to depassivation,leading to the massive growth of metastable pitting and stable pitting.The depassivation of304L SS was found to be dominant at the stable period of CE where serious localized corrosion occurred.展开更多
Conventional,submicron and multimodal WC-12Co cermet coatings were deposited by high velocity oxy-fuel（HVOF）.The microhardness and microstructure of the coatings were compared,and the resistance of the coatings to c...Conventional,submicron and multimodal WC-12Co cermet coatings were deposited by high velocity oxy-fuel（HVOF）.The microhardness and microstructure of the coatings were compared,and the resistance of the coatings to cavitation erosion was studied by ultrasonic vibration cavitation equipment.Cavitation pits and craters were observed by SEM and cavitation mechanisms were explored.The results show that the microstructures of submicron and multimodal WC-12Co coatings prepared by HVOF are dense with little porosity,and their microhardness values are obviously higher than that of the conventional WC-12Co coating.The average microhardness of multimodal WC-12Co coating reaches nearly HV1500,which is much higher than that of the conventional one.As well,it is found that the multimodal WC-12Co coating exhibits the best cavitation erosion resistance among the three coatings,the erosion rate is approximately 40% that of the conventional coating,and the cavitation erosion resistance of multimodal WC-12Co coating is enhanced by above 150% in comparison with the conventional coating.展开更多
A new kind of multi-dimensional WC-10Co4Cr coating which is composed of nano,submicron,micron WC grains and CoCr alloy,was developed by high velocity oxy-fuel(HVOF)spraying.Porosity,microhardness,fracture toughness an...A new kind of multi-dimensional WC-10Co4Cr coating which is composed of nano,submicron,micron WC grains and CoCr alloy,was developed by high velocity oxy-fuel(HVOF)spraying.Porosity,microhardness,fracture toughness and cavitation erosion resistance of the multi-dimensional coating were investigated in comparison with the bimodal and nanostructured WC?10Co4Cr coatings.Moreover,the cavitation erosion behavior and mechanism of the multi-dimensional coating were explored.Results show that HVOF sprayed multi-dimensional WC-10Co4Cr coating possesses low porosity(≤0.32%)and high fracture toughness without obvious nano WC decarburization during spraying.Furthermore,it is discovered that the multi-dimensional WC-10Co4Cr coating exhibits the best cavitation erosion resistance which is enhanced by approximately 28%and 34%,respectively,compared with the nanostructured and bimodal coatings in fresh water.The superior cavitation resistance of multi-dimensional WC-10Co4Cr coating may originate from the unique micro?nano structure and excellent properties,which can effectively obstruct the formation and propagation of cavitation erosion cracks.展开更多
The WC powder was precoated on the surface of CrNiMo stainless steel and then made into an alloying layer by using the laser alloying technique. Phases in the layers were investigated by X-ray diffraction （XRD） anal...The WC powder was precoated on the surface of CrNiMo stainless steel and then made into an alloying layer by using the laser alloying technique. Phases in the layers were investigated by X-ray diffraction （XRD） analysis and surface morphologies after cavitation erosion were observed with the help of scanning electron microscopy （SEM）. The cavitation erosion behavior of the CrNiMo stainless steel and WC laser alloying layer in distilled water was tested with the help of ultrasonic vibration cavitation erosion equipment. The results showed that the thickness of the laser alloying layer was about 0.13 mm. The layer had a dense microstructure, metallurgically bonded to the substrate, and no crack had been found. The cavitation erosion mass loss rate of the laser alloying layer was only 2/5 that of the CrNiMo stainless steel. The layer had better cavitation resistance properties because of its metallurgical combination and the strengthening effects of the precipitate phases.展开更多
Friction stir processing of an Al0.1CoCrFeNi high entropy alloy(HEA)was performed at controlled cooling conditions(ambient and liquid submerged).Microstructural and mechanical characterization of the processed and as-...Friction stir processing of an Al0.1CoCrFeNi high entropy alloy(HEA)was performed at controlled cooling conditions(ambient and liquid submerged).Microstructural and mechanical characterization of the processed and as-cast HEAs was evaluated using electron backscatter diffraction,micro-hardness testing and nanoindentation.HEA under the submerged cooling condition showed elongated grains(10μm)with fine equiaxed grains(2μm)along the boundary compared to the coarser grain(~2 mm)of as-cast HEA.The hardness showed remarkable improvements with four(submerged cooling condition)and three(ambient cooling condition)times that of as-cast HEA(HV^150).The enhanced hardness is attributed to the significant grain refinement in the processed HEAs.Cavitation erosion behavior was observed for samples using an ultrasonication method.All of the HEAs showed better cavitation erosion resistance than the stainless steel 316L.The sample processed under a submerged liquid condition showed approximately 20 and 2 times greater erosion resistance than stainless steel 316L and ascast HEA,respectively.The enhanced erosion resistances of the processed HEAs correlate to their increased hardness,resistance to plasticity,and better yield strength than the as-cast HEA.The surface of the tested samples showed nucleation and pit growth,and plastic deformation of the material followed by fatigue-controlled disintegration as the primary material removal mechanism.展开更多
Cavitation erosion （CE） is the predominant cause for the failure of overflow components in fluid machinery. Advanced coatings have provided an effective solution to cavitation erosion due to the rapid development of...Cavitation erosion （CE） is the predominant cause for the failure of overflow components in fluid machinery. Advanced coatings have provided an effective solution to cavitation erosion due to the rapid development of surface engineering techniques. However, the influence of coating structures on CE resistance has not been sys- tematically studied. To better understand their relationship, micro-nano and conventional WC-10Co4Cr cermet coat- ings are deposited by high velocity oxygen fuel spray- ing（HVOF）, and their microstructures are analyzed by OM, SEM and XRD. Meanwhile, characterizations of mechan- ical and electrochemical properties of the coatings are carried out, as well as the coatings＇ resistance to CE in 3.5 wt % NaC1 solution, and the cavitation mechanisms are explored. Results show that micro-nano WC-10Co4Cr coating possesses dense microstructure, excellent mechanical and electrochemical properties, with very low porosity of 0.26 4-0.07% and extraordinary fracture toughness of 5.58 4-0.51 MPa.m1/2. Moreover, the CE resistance of micro-nano coating is enhanced above 50% than conventional coating at the steady CE period in 3.5 wt % NaC1 solution. The superior CE resistance of micro- nano WC-10Co4Cr coating may originate from the unique micro-nano structure and properties, which can effectively obstruct the formation and propagation of CE crack. Thus,a new method is proposed to enhance the CE resistance of WC-10Co4Cr coating by manipulating the microstructure.展开更多
The cavitation erosion (CE) behavior of CrMnIM ferrite-austenite duplex stainless steel in distilled water and 3% NaCI solution was investigated by using a magnetostrictive-induced CE facility. The damaged surfaces we...The cavitation erosion (CE) behavior of CrMnIM ferrite-austenite duplex stainless steel in distilled water and 3% NaCI solution was investigated by using a magnetostrictive-induced CE facility. The damaged surfaces were observed by scanning electron microscope (SEM). It was found that the CE resistance of CrMnN steel was higher than that of OCrl3Ni5Mo steel. The mass loss rate of CrMnN steel in distilled water was similar to that in 3% NaCI except at the early stage of CE. The failure mode of ferrite phase was brittle fracture, which had adverse effect on the resistance to CE, while the failure of austenite phase was a ductile failure in CrMnN steel. The excellent resistance to CE was related to the good mechanical properties of austenitic phase and the consumption of CE energy by plastic deformation involving slip and twinning.展开更多
The microstructure,corrosion and cavitation erosion(CE)behaviors of the as-cast and four different heat treated nickel aluminum bronzes(NABs)in 3.5 wt.%NaCl solution were investigated.The results show that after annea...The microstructure,corrosion and cavitation erosion(CE)behaviors of the as-cast and four different heat treated nickel aluminum bronzes(NABs)in 3.5 wt.%NaCl solution were investigated.The results show that after annealing,β′transformed into the eutectoid microstructure,and moreκIV precipitated fromα.Less eutectoid microstructure and moreβ′were obtained after normalizing.The quenched NAB mainly consisted ofαandβ′phases,and fine,acicularαandκphases precipitated insideβ′after subsequent aging.The largest proportion of the eutectoid microstructure,which underwent severe selective phase corrosion,was responsible for the lowest corrosion resistance of the annealed NAB.The quenched NAB possessed the most protective film and hence the highest corrosion resistance.The mechanical attack was primarily responsible for the CE damage for the as-cast,annealed and normarlized NABs.The quenched and quenched+aged NABs exhibited superior CE resistance because of the high hardness.The CE−corrosion synergy dominantly caused CE degradation,and it was largely attributed to corrosion-enhanced-CE.展开更多
A simulating experimental device for journal bearings of engines is established by use of the mechanism of ultrasonic vibration This device can make the pressure inside the oil film changed at ultrasonic frequency,wh...A simulating experimental device for journal bearings of engines is established by use of the mechanism of ultrasonic vibration This device can make the pressure inside the oil film changed at ultrasonic frequency,which enable the specimen surface to be damaged by cavitation erosion in a comparatively short time Connecting with the bubbly oil producing device,this rig can investigate the influence of bubbly oil on the cavitation erosion Through detailed experimental research it is found that the bubbly oil decreases the cavitation erosion in journal bearings of engines This result is analyzed reasonably from mechanism of cavitation erosion.展开更多
Cavitation,a phenomenon produced by a moving fluid,is ubiquitous in the water environment of the Earth's surface and its related mechanical action in the process of cavitation leads to the widespread erosion of ro...Cavitation,a phenomenon produced by a moving fluid,is ubiquitous in the water environment of the Earth's surface and its related mechanical action in the process of cavitation leads to the widespread erosion of rock in nature.Although the mechanical action of flowing water body that accelerates the rock mass loss and fragmentation of rock(abrasion,erosion,and etching)and other phenomena have been much studied,its acceleration of mineral crystal dissolution is rarely reported.The physical mechanism of effect is not yet clear.The cavitation bubble produced in the cavitation process is at the micron level,and its related mechanical action leading to the accumulation of rock mineral dissolution is manifested in time and space in the process of the chemical element's migration between water and rock minerals.Cavitation erosion may be one of the important driving forces for the migration of geochemical elements within the lithosphere and hydrosphere.In this paper,based on the crystal dissolution stepwave dynamic theory and the theoretical derivation and calculation of Gibbs free energy change of the mineral crystals plastic deformation which caused by the mechanical action of cavitation erosion,we give the possible mechanism of accelerating the transient dissolution of mineral crystals by cavitation erosion—the cavitation bubbles on the surface of the near crystal release the high speed micro-jet and shock wave perpendicular to the surface during the collapsing,in which the water hammer pressure produced by micro-jet at the solid–liquid interface causes instantaneous plastic deformation on the crystal surface under the condition that it is larger than the yield stress of the crystal.Under the influence of the thermal effect of the plastic deformation process and the change of Gibbs free energy(the dislocation elastic strain energy of plastic deformation on the crystal surface may be included),the local instantaneous dissolution rate of the mineral surface is accelerated.The continuous cavitation erosion eventually causes fracture and breaking of the mineral crystal,meanwhile,the Gibbs–Thomson effect may enhance the dissolution of mineral crystals more prominently.At the same time,the correctness of the mechanism is verified qualitatively by the acoustic cavitation experiment with the same erosion mechanism.展开更多
Cavitation erosion is an especially destructive and complex phenomenon. To understand its basic mechanism, the fatigue process of materials during cavitation erosion was investigated by numerical simulation technology...Cavitation erosion is an especially destructive and complex phenomenon. To understand its basic mechanism, the fatigue process of materials during cavitation erosion was investigated by numerical simulation technology. The loading spectrum used was generated by a spark-discharged electrode. Initiation crack life and true stress amplitude was used to explain the cavitation failure period and damage mechanism. The computational results indicated that the components of different materials exhibited various fatigue lives under the same external conditions. When the groove depth was extended, the initiation crack life decreased rapidly, while the true stress amplitude was increased simultaneously. This gave an important explanation to the accelerating material loss rate during cavitation erosion. However, when the groove depth was fixed and the length varied, the fatigue life became complex, more fluctuant than that happened in depth. The results also indicate that the fatigue effect of cavitation plays an important role in contributing to the formation and propagation of characteristic pits.展开更多
Isostatic graphite materials with 8%porosity and 14%porosity were prepared by the cold isostatic pressing process.Cavitation erosion resistance of the isostatic graphite was evaluated through cavitation tests in an ul...Isostatic graphite materials with 8%porosity and 14%porosity were prepared by the cold isostatic pressing process.Cavitation erosion resistance of the isostatic graphite was evaluated through cavitation tests in an ultrasonic vibration system.The volume loss and erosion morphology of the isostatic graphite were adopted to investigate the cavitation erosion resistance of the isostatic graphite.The cavitation test results show that after ultrasonic vibration of 14 h,the volume loss of the isostatic graphite materials with 8%porosity and 14%porosity are 35%and 46%of the carbon graphite material,respectively.The isostatic graphite material with 8%porosity exhibits an outstanding capability to resist cavitation erosion damage,and the cavitation erosion resistance of the isostatic graphite enhances with the decrease in porosity.The damage mechanism of isostatic graphite is brittle fracture attributed to the shock wave and micro jet.The isostatic graphite with low porosity exhibits excellent cavitation erosion resistance due to its fine graphite particles,homogeneous structure and high degree of hardness.展开更多
Cavitation erosion behavior of as-welded Cu12Mn8Al3Fe2Ni alloy in 3.5% NaCl aqueous solution was studied bymagnetostrictive vibratory device for cavitation erosion. The results show that the cavitation erosion resista...Cavitation erosion behavior of as-welded Cu12Mn8Al3Fe2Ni alloy in 3.5% NaCl aqueous solution was studied bymagnetostrictive vibratory device for cavitation erosion. The results show that the cavitation erosion resistance ofthe as-welded Cu12Mn8Al3Fe2Ni alloy is much more superior to that of the as-cast one. The cumulative mass lossand the mass loss rate of the as-welded Cu12Mn8Al3Fe2Ni alloy are almost 1/4 that of the as-cast one. SEM analysisof eroded specimens reveals that the as-cast Cu12Mn8Al3Fe2Ni alloy is attacked more severely than the as-weldedone. Microcracks causing cavitation damage initiate at the phase boundaries.展开更多
The characteristics of microstructure changes during cavitation erosion (CE) were investigated by the use of XRD and TEM analyses for steel (ZG0Cr13Mn8N) with metastable austenite. The results show that the microstruc...The characteristics of microstructure changes during cavitation erosion (CE) were investigated by the use of XRD and TEM analyses for steel (ZG0Cr13Mn8N) with metastable austenite. The results show that the microstructure of the surface layer of the specimens consists of α'-martensite, metastable austenite and a few ε-martensite before CE. CE obviously increases dislocation density and straight or planar dislocations on the surface, and induces γ->ε,ε-> α' and γ->α'-martensitic transformation.展开更多
For the evaluation of cavitation erosion resistance of metallic materials,it has always been a time-consuming technical problem.This paper innovatively proposed a parameter named cavitation hardening rate to character...For the evaluation of cavitation erosion resistance of metallic materials,it has always been a time-consuming technical problem.This paper innovatively proposed a parameter named cavitation hardening rate to characterize the plastic deformation and work hardening behavior of metallic materials during the cavitation process and then found a positive correlation between cavitation hardening rate and strain hardening index.Finally,the relationship between cavitation volume loss and strain hardening index was obtained,and a simple and rapid evaluation method for cavitation erosion resistance was established.展开更多
To investigate the mechanism of cavitation erosion caused by laser-induced single bubble near the surface coating alloy coating material, we utilized a nanosecond resolution photography system based on a Q-switched Nd...To investigate the mechanism of cavitation erosion caused by laser-induced single bubble near the surface coating alloy coating material, we utilized a nanosecond resolution photography system based on a Q-switched Nd: YAG laser and conventional industrial camera to carefully observe the transient process of bubble collapse under different conditions. We analyzed the generation of collapse microjets and the emission of collapse shock waves and explored the cavitation erosion characteristics caused by laser-induced single bubble collapse. We discovered that even on surfaces of highly hard and corrosion-resistant alloy coatings, severe cavitation erosion occurred, and there was a phenomenon of mismatch between the cavitation erosion location and the bubble projection position. The intensity of cavitation erosion depended on the energy self-focusing effect of the collapse shockwaves. In the experiments, we also observed the self-focusing phenomenon of collapse shockwaves under different conditions. The self-focusing effect of collapse shockwaves weakened as the distance between the bubble and the material surface increased, which may be the cause of cavitation erosion induced by a laser-induced single bubble.展开更多
Over the past 60 years, the air concentration in water has been considered as a control index of cavitation erosion reduction and widely used in the designs of hydraulic structures. However, the mechanism of air entra...Over the past 60 years, the air concentration in water has been considered as a control index of cavitation erosion reduction and widely used in the designs of hydraulic structures. However, the mechanism of air entrainment against cavitation erosion has been paid good attention to. In the present work, the effect of air bubble size on cavitation erosion reduction was experimentally investigated. A device with micron-scale orifice diameters(10, 20 and 50 μm in size) was specially designed to introduce air bubbles into water. The experiments about the effect of air bubble size were conducted by means of a vibratory apparatus, including the behavior of formation and movement for single air bubble, the characteristics of cavitation erosion reduction at different air entrainment conditions. The findings demonstrate that high air concentration has significant effects on cavitation erosion reduction.But, a notable problem was that the size of air bubbles is of outstanding effect on cavitation erosion reduction. Small air bubbles support to alleviate cavitation erosion, even at same air concentration.展开更多
The corrosion and cavitation erosion behaviors of two main materials for ship propellers, i.e., nickel-aluminum bronze （NAB） and manganese-nickel-aluminum bronze （MAB） were investigated in a clean and sulfide-poll...The corrosion and cavitation erosion behaviors of two main materials for ship propellers, i.e., nickel-aluminum bronze （NAB） and manganese-nickel-aluminum bronze （MAB） were investigated in a clean and sulfide-polluted 3.5% NaCl solutions. The presence of sulfide increased the corrosion damage of both NAB and MAB by rendering the corrosion product film thicker, more porous and less protective. For MAB, the formation of Fe oxides/sulfides within the corrosion product film may reduce the film compactness and responsible for the lower corrosion resistance, compared with NAB. The presence of sulfide caused the occurrence of more severe corrosion on the surface and therefore further enhanced the cavitation erosion damage. Compared with the result in the clean solution, the cavitation-erosion mass loss rate was raised by a factor of about 11.88% for MAB, and 58.6% for NAB. For NAB, the mechanical erosion dominated the damage in the clean solution, while the cavitation erosion synergy made a significant contribution to the overall damage in the sulfide-polluted solution. For MAB, it was the mechanical damage that contributed mainly to the cavitation erosion damage in both solutions. The exfoliation of large-sized κ phase and the cleavage rupture of β phases resulted in lower cavitation erosion resistance of MAB, compared with NAB.展开更多
The investigate about the effect of the microstructure of Ti6Al4V alloy on its cavitation erosion and corrosion properties in marine can provide the key basis for the application.On the basis of as-received Ti6Al4V(TC...The investigate about the effect of the microstructure of Ti6Al4V alloy on its cavitation erosion and corrosion properties in marine can provide the key basis for the application.On the basis of as-received Ti6Al4V(TC4)alloy,FC-TC4 and AC-TC4 alloys were prepared by heat treatment with the cooling method of a furnace and atmospheric environment,respectively.Then the microstructure evolutions of three samples were scrutinized and the effect of microstructure on their cavitation erosion and corrosion resistance was explored.The results showed that more recrystallized grains formed as well as its content of α grains and high-angle grain boundaries increased in AC-TC4 alloy.To FC-TC4 alloy,there was obvious grain growth apart from recrystallization.Moreover,many nanotwins of Ti V and Ti Al_(3)were formed separately in FC-TC4 and AC-TC4 alloys due to the dislocation migration during heat treatment.The microstructure evolution led the hardness and elastic modulus of AC-TC4 alloy were the best,followed by FC-TC4 alloy,that of TC4 were the worst.Similarly,passivating ability of AC-TC4 alloy was the best among three samples because of its microstructure.Although cracks extended along the grain boundaries under the action of continual cavitation erosion,the passivation film formed by TiO_(2) and Al_(2)O_(3) would enhance their resistance to further corrosion and cavitation erosion in artificial seawater.展开更多
The cavitation erosion corrosion behaviour of ZQMn12-8-3-2 manganese-nickel-aluminum bronze and ZHMn55- 3-1 manganese-brass was investigated by mass loss, electrochemical measurements （polarization curves and electro...The cavitation erosion corrosion behaviour of ZQMn12-8-3-2 manganese-nickel-aluminum bronze and ZHMn55- 3-1 manganese-brass was investigated by mass loss, electrochemical measurements （polarization curves and electrochemical impedance spectroscopy） and the cavitation damaged surfaces were observed by scanning electron microscopy （SEM）. The results showed that ZQMn12-8-3-2 had better cavitation erosion resistance than ZHMn55-3-1. After the cavitation erosion for 6 h, the cumulative mass loss of ZQMn12-8-3-2 was about 1/3 that of ZHMn55-3-1. The corrosion current density of ZQMn12-8-3-2 was less than that of ZHMn55-3-1 under both static and cavitaiton condition. The free-corrosion potentials of ZQMn12-8-3-2 and ZHMn55-3-1 were all shifted in positive direction under cavitation condition compared to static condition. In the total cumulative mass loss under cavitation condition, the pure erosion played a key role for the two tested materials （74% for ZHMn55-3-1 and 60% for ZQMn12-8-3-2）, and the total synergism between corrosion and erosion of ZQMn12-8-3-2 （39%） was larger than that of ZHMn55-3-1 （23%）. The high cavitation erosion resistance of ZQMn12-8-3-2 was mainly attributed to its lower stacking fault energy （SFE）, the higher microhardness and work-hardening ability as well as the favorable propagation of cavitation cracks for ZQMn12-8-3-2, i.e., parallel to the surface rather than perpendicular to the surface for ZHMn55-3-1.展开更多
基金financially supported of the National Natural Science Foundation of China (Nos.52101105 and 51975263)。
文摘The corrosion behavior of 304L stainless steel(SS)in 3.5wt%NaCl solution after different cavitation erosion(CE)times was mainly evaluated using electrochemical noise and potentiostatic polarization techniques.It was found that the antagonism effect resulting in the passivation and depassivation of 304L SS had significant distinctions at different CE periods.The passive behavior was predominant during the incubation period of CE where the metastable pitting initiated at the surface of 304L SS.Over the rising period of CE,the 304L SS experienced a transition from passivation to depassivation,leading to the massive growth of metastable pitting and stable pitting.The depassivation of304L SS was found to be dominant at the stable period of CE where serious localized corrosion occurred.
基金Project(50479016) supported by the National Natural Science Foundation of China
文摘Conventional,submicron and multimodal WC-12Co cermet coatings were deposited by high velocity oxy-fuel（HVOF）.The microhardness and microstructure of the coatings were compared,and the resistance of the coatings to cavitation erosion was studied by ultrasonic vibration cavitation equipment.Cavitation pits and craters were observed by SEM and cavitation mechanisms were explored.The results show that the microstructures of submicron and multimodal WC-12Co coatings prepared by HVOF are dense with little porosity,and their microhardness values are obviously higher than that of the conventional WC-12Co coating.The average microhardness of multimodal WC-12Co coating reaches nearly HV1500,which is much higher than that of the conventional one.As well,it is found that the multimodal WC-12Co coating exhibits the best cavitation erosion resistance among the three coatings,the erosion rate is approximately 40% that of the conventional coating,and the cavitation erosion resistance of multimodal WC-12Co coating is enhanced by above 150% in comparison with the conventional coating.
基金Projects(51422507,51379168)supported by the National Natural Science Foundation of China
文摘A new kind of multi-dimensional WC-10Co4Cr coating which is composed of nano,submicron,micron WC grains and CoCr alloy,was developed by high velocity oxy-fuel(HVOF)spraying.Porosity,microhardness,fracture toughness and cavitation erosion resistance of the multi-dimensional coating were investigated in comparison with the bimodal and nanostructured WC?10Co4Cr coatings.Moreover,the cavitation erosion behavior and mechanism of the multi-dimensional coating were explored.Results show that HVOF sprayed multi-dimensional WC-10Co4Cr coating possesses low porosity(≤0.32%)and high fracture toughness without obvious nano WC decarburization during spraying.Furthermore,it is discovered that the multi-dimensional WC-10Co4Cr coating exhibits the best cavitation erosion resistance which is enhanced by approximately 28%and 34%,respectively,compared with the nanostructured and bimodal coatings in fresh water.The superior cavitation resistance of multi-dimensional WC-10Co4Cr coating may originate from the unique micro?nano structure and excellent properties,which can effectively obstruct the formation and propagation of cavitation erosion cracks.
文摘The WC powder was precoated on the surface of CrNiMo stainless steel and then made into an alloying layer by using the laser alloying technique. Phases in the layers were investigated by X-ray diffraction （XRD） analysis and surface morphologies after cavitation erosion were observed with the help of scanning electron microscopy （SEM）. The cavitation erosion behavior of the CrNiMo stainless steel and WC laser alloying layer in distilled water was tested with the help of ultrasonic vibration cavitation erosion equipment. The results showed that the thickness of the laser alloying layer was about 0.13 mm. The layer had a dense microstructure, metallurgically bonded to the substrate, and no crack had been found. The cavitation erosion mass loss rate of the laser alloying layer was only 2/5 that of the CrNiMo stainless steel. The layer had better cavitation resistance properties because of its metallurgical combination and the strengthening effects of the precipitate phases.
文摘Friction stir processing of an Al0.1CoCrFeNi high entropy alloy(HEA)was performed at controlled cooling conditions(ambient and liquid submerged).Microstructural and mechanical characterization of the processed and as-cast HEAs was evaluated using electron backscatter diffraction,micro-hardness testing and nanoindentation.HEA under the submerged cooling condition showed elongated grains(10μm)with fine equiaxed grains(2μm)along the boundary compared to the coarser grain(~2 mm)of as-cast HEA.The hardness showed remarkable improvements with four(submerged cooling condition)and three(ambient cooling condition)times that of as-cast HEA(HV^150).The enhanced hardness is attributed to the significant grain refinement in the processed HEAs.Cavitation erosion behavior was observed for samples using an ultrasonication method.All of the HEAs showed better cavitation erosion resistance than the stainless steel 316L.The sample processed under a submerged liquid condition showed approximately 20 and 2 times greater erosion resistance than stainless steel 316L and ascast HEA,respectively.The enhanced erosion resistances of the processed HEAs correlate to their increased hardness,resistance to plasticity,and better yield strength than the as-cast HEA.The surface of the tested samples showed nucleation and pit growth,and plastic deformation of the material followed by fatigue-controlled disintegration as the primary material removal mechanism.
基金Supported by National Natural Science Foundation of China (Grand No. 51422507)
文摘Cavitation erosion （CE） is the predominant cause for the failure of overflow components in fluid machinery. Advanced coatings have provided an effective solution to cavitation erosion due to the rapid development of surface engineering techniques. However, the influence of coating structures on CE resistance has not been sys- tematically studied. To better understand their relationship, micro-nano and conventional WC-10Co4Cr cermet coat- ings are deposited by high velocity oxygen fuel spray- ing（HVOF）, and their microstructures are analyzed by OM, SEM and XRD. Meanwhile, characterizations of mechan- ical and electrochemical properties of the coatings are carried out, as well as the coatings＇ resistance to CE in 3.5 wt % NaC1 solution, and the cavitation mechanisms are explored. Results show that micro-nano WC-10Co4Cr coating possesses dense microstructure, excellent mechanical and electrochemical properties, with very low porosity of 0.26 4-0.07% and extraordinary fracture toughness of 5.58 4-0.51 MPa.m1/2. Moreover, the CE resistance of micro-nano coating is enhanced above 50% than conventional coating at the steady CE period in 3.5 wt % NaC1 solution. The superior CE resistance of micro- nano WC-10Co4Cr coating may originate from the unique micro-nano structure and properties, which can effectively obstruct the formation and propagation of CE crack. Thus,a new method is proposed to enhance the CE resistance of WC-10Co4Cr coating by manipulating the microstructure.
基金Tbe authors acknowledge the financial support of the National Natural Science Foundation of China(59831030)the Special Funds for the Major State Basic Research Projects G19990650.
文摘The cavitation erosion (CE) behavior of CrMnIM ferrite-austenite duplex stainless steel in distilled water and 3% NaCI solution was investigated by using a magnetostrictive-induced CE facility. The damaged surfaces were observed by scanning electron microscope (SEM). It was found that the CE resistance of CrMnN steel was higher than that of OCrl3Ni5Mo steel. The mass loss rate of CrMnN steel in distilled water was similar to that in 3% NaCI except at the early stage of CE. The failure mode of ferrite phase was brittle fracture, which had adverse effect on the resistance to CE, while the failure of austenite phase was a ductile failure in CrMnN steel. The excellent resistance to CE was related to the good mechanical properties of austenitic phase and the consumption of CE energy by plastic deformation involving slip and twinning.
基金financially supported by the Fundamental Research Funds for the Central Universities of China (Nos. B210203049, B210204005)the Natural Science Foundation of Jiangsu Province, China (No. BK20191161)+1 种基金the Changzhou Sci & Tech Program, China (No. CJ20210154)the National Natural Science Foundation of China (Nos. 51601058, 51879089)
文摘The microstructure,corrosion and cavitation erosion(CE)behaviors of the as-cast and four different heat treated nickel aluminum bronzes(NABs)in 3.5 wt.%NaCl solution were investigated.The results show that after annealing,β′transformed into the eutectoid microstructure,and moreκIV precipitated fromα.Less eutectoid microstructure and moreβ′were obtained after normalizing.The quenched NAB mainly consisted ofαandβ′phases,and fine,acicularαandκphases precipitated insideβ′after subsequent aging.The largest proportion of the eutectoid microstructure,which underwent severe selective phase corrosion,was responsible for the lowest corrosion resistance of the annealed NAB.The quenched NAB possessed the most protective film and hence the highest corrosion resistance.The mechanical attack was primarily responsible for the CE damage for the as-cast,annealed and normarlized NABs.The quenched and quenched+aged NABs exhibited superior CE resistance because of the high hardness.The CE−corrosion synergy dominantly caused CE degradation,and it was largely attributed to corrosion-enhanced-CE.
文摘A simulating experimental device for journal bearings of engines is established by use of the mechanism of ultrasonic vibration This device can make the pressure inside the oil film changed at ultrasonic frequency,which enable the specimen surface to be damaged by cavitation erosion in a comparatively short time Connecting with the bubbly oil producing device,this rig can investigate the influence of bubbly oil on the cavitation erosion Through detailed experimental research it is found that the bubbly oil decreases the cavitation erosion in journal bearings of engines This result is analyzed reasonably from mechanism of cavitation erosion.
基金financially supported by Key Research of Frontier Science, CAS, Grant. NO. QYZDY-SSWDQC010
文摘Cavitation,a phenomenon produced by a moving fluid,is ubiquitous in the water environment of the Earth's surface and its related mechanical action in the process of cavitation leads to the widespread erosion of rock in nature.Although the mechanical action of flowing water body that accelerates the rock mass loss and fragmentation of rock(abrasion,erosion,and etching)and other phenomena have been much studied,its acceleration of mineral crystal dissolution is rarely reported.The physical mechanism of effect is not yet clear.The cavitation bubble produced in the cavitation process is at the micron level,and its related mechanical action leading to the accumulation of rock mineral dissolution is manifested in time and space in the process of the chemical element's migration between water and rock minerals.Cavitation erosion may be one of the important driving forces for the migration of geochemical elements within the lithosphere and hydrosphere.In this paper,based on the crystal dissolution stepwave dynamic theory and the theoretical derivation and calculation of Gibbs free energy change of the mineral crystals plastic deformation which caused by the mechanical action of cavitation erosion,we give the possible mechanism of accelerating the transient dissolution of mineral crystals by cavitation erosion—the cavitation bubbles on the surface of the near crystal release the high speed micro-jet and shock wave perpendicular to the surface during the collapsing,in which the water hammer pressure produced by micro-jet at the solid–liquid interface causes instantaneous plastic deformation on the crystal surface under the condition that it is larger than the yield stress of the crystal.Under the influence of the thermal effect of the plastic deformation process and the change of Gibbs free energy(the dislocation elastic strain energy of plastic deformation on the crystal surface may be included),the local instantaneous dissolution rate of the mineral surface is accelerated.The continuous cavitation erosion eventually causes fracture and breaking of the mineral crystal,meanwhile,the Gibbs–Thomson effect may enhance the dissolution of mineral crystals more prominently.At the same time,the correctness of the mechanism is verified qualitatively by the acoustic cavitation experiment with the same erosion mechanism.
基金the National High-Tech Research and Development Program of China(No.2002AA331080)the Beijing Important Science Technology Projects(No.H024200050021).
文摘Cavitation erosion is an especially destructive and complex phenomenon. To understand its basic mechanism, the fatigue process of materials during cavitation erosion was investigated by numerical simulation technology. The loading spectrum used was generated by a spark-discharged electrode. Initiation crack life and true stress amplitude was used to explain the cavitation failure period and damage mechanism. The computational results indicated that the components of different materials exhibited various fatigue lives under the same external conditions. When the groove depth was extended, the initiation crack life decreased rapidly, while the true stress amplitude was increased simultaneously. This gave an important explanation to the accelerating material loss rate during cavitation erosion. However, when the groove depth was fixed and the length varied, the fatigue life became complex, more fluctuant than that happened in depth. The results also indicate that the fatigue effect of cavitation plays an important role in contributing to the formation and propagation of characteristic pits.
基金The National Natural Science Foundation of China(No.51635004,11472078)。
文摘Isostatic graphite materials with 8%porosity and 14%porosity were prepared by the cold isostatic pressing process.Cavitation erosion resistance of the isostatic graphite was evaluated through cavitation tests in an ultrasonic vibration system.The volume loss and erosion morphology of the isostatic graphite were adopted to investigate the cavitation erosion resistance of the isostatic graphite.The cavitation test results show that after ultrasonic vibration of 14 h,the volume loss of the isostatic graphite materials with 8%porosity and 14%porosity are 35%and 46%of the carbon graphite material,respectively.The isostatic graphite material with 8%porosity exhibits an outstanding capability to resist cavitation erosion damage,and the cavitation erosion resistance of the isostatic graphite enhances with the decrease in porosity.The damage mechanism of isostatic graphite is brittle fracture attributed to the shock wave and micro jet.The isostatic graphite with low porosity exhibits excellent cavitation erosion resistance due to its fine graphite particles,homogeneous structure and high degree of hardness.
文摘Cavitation erosion behavior of as-welded Cu12Mn8Al3Fe2Ni alloy in 3.5% NaCl aqueous solution was studied bymagnetostrictive vibratory device for cavitation erosion. The results show that the cavitation erosion resistance ofthe as-welded Cu12Mn8Al3Fe2Ni alloy is much more superior to that of the as-cast one. The cumulative mass lossand the mass loss rate of the as-welded Cu12Mn8Al3Fe2Ni alloy are almost 1/4 that of the as-cast one. SEM analysisof eroded specimens reveals that the as-cast Cu12Mn8Al3Fe2Ni alloy is attacked more severely than the as-weldedone. Microcracks causing cavitation damage initiate at the phase boundaries.
文摘The characteristics of microstructure changes during cavitation erosion (CE) were investigated by the use of XRD and TEM analyses for steel (ZG0Cr13Mn8N) with metastable austenite. The results show that the microstructure of the surface layer of the specimens consists of α'-martensite, metastable austenite and a few ε-martensite before CE. CE obviously increases dislocation density and straight or planar dislocations on the surface, and induces γ->ε,ε-> α' and γ->α'-martensitic transformation.
基金funded by the National Key Research and Development Program of China(2022YFB3705803)the National Natural Science Foundation of China(No.52031007)+1 种基金the Natural Science Foundation of Tianjin(22JCQNJC00950)the Scientific and Technological Project of Yunnan Precious Metals Laboratory(YPML-2023050275).
文摘For the evaluation of cavitation erosion resistance of metallic materials,it has always been a time-consuming technical problem.This paper innovatively proposed a parameter named cavitation hardening rate to characterize the plastic deformation and work hardening behavior of metallic materials during the cavitation process and then found a positive correlation between cavitation hardening rate and strain hardening index.Finally,the relationship between cavitation volume loss and strain hardening index was obtained,and a simple and rapid evaluation method for cavitation erosion resistance was established.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.52179092,52222904).
文摘To investigate the mechanism of cavitation erosion caused by laser-induced single bubble near the surface coating alloy coating material, we utilized a nanosecond resolution photography system based on a Q-switched Nd: YAG laser and conventional industrial camera to carefully observe the transient process of bubble collapse under different conditions. We analyzed the generation of collapse microjets and the emission of collapse shock waves and explored the cavitation erosion characteristics caused by laser-induced single bubble collapse. We discovered that even on surfaces of highly hard and corrosion-resistant alloy coatings, severe cavitation erosion occurred, and there was a phenomenon of mismatch between the cavitation erosion location and the bubble projection position. The intensity of cavitation erosion depended on the energy self-focusing effect of the collapse shockwaves. In the experiments, we also observed the self-focusing phenomenon of collapse shockwaves under different conditions. The self-focusing effect of collapse shockwaves weakened as the distance between the bubble and the material surface increased, which may be the cause of cavitation erosion induced by a laser-induced single bubble.
基金supported by the National Natural Science Foundation of China(Grant No.51409187)the Fundamental Research Funds for the Central Universities(Grant No.2016B09914)
文摘Over the past 60 years, the air concentration in water has been considered as a control index of cavitation erosion reduction and widely used in the designs of hydraulic structures. However, the mechanism of air entrainment against cavitation erosion has been paid good attention to. In the present work, the effect of air bubble size on cavitation erosion reduction was experimentally investigated. A device with micron-scale orifice diameters(10, 20 and 50 μm in size) was specially designed to introduce air bubbles into water. The experiments about the effect of air bubble size were conducted by means of a vibratory apparatus, including the behavior of formation and movement for single air bubble, the characteristics of cavitation erosion reduction at different air entrainment conditions. The findings demonstrate that high air concentration has significant effects on cavitation erosion reduction.But, a notable problem was that the size of air bubbles is of outstanding effect on cavitation erosion reduction. Small air bubbles support to alleviate cavitation erosion, even at same air concentration.
基金supported by the Fundamental Research Funds for the Central Universities of China (Nos. 2015B30314 and 2014B11614)the National Natural Science Foundation of China (No. 51601058)
文摘The corrosion and cavitation erosion behaviors of two main materials for ship propellers, i.e., nickel-aluminum bronze （NAB） and manganese-nickel-aluminum bronze （MAB） were investigated in a clean and sulfide-polluted 3.5% NaCl solutions. The presence of sulfide increased the corrosion damage of both NAB and MAB by rendering the corrosion product film thicker, more porous and less protective. For MAB, the formation of Fe oxides/sulfides within the corrosion product film may reduce the film compactness and responsible for the lower corrosion resistance, compared with NAB. The presence of sulfide caused the occurrence of more severe corrosion on the surface and therefore further enhanced the cavitation erosion damage. Compared with the result in the clean solution, the cavitation-erosion mass loss rate was raised by a factor of about 11.88% for MAB, and 58.6% for NAB. For NAB, the mechanical erosion dominated the damage in the clean solution, while the cavitation erosion synergy made a significant contribution to the overall damage in the sulfide-polluted solution. For MAB, it was the mechanical damage that contributed mainly to the cavitation erosion damage in both solutions. The exfoliation of large-sized κ phase and the cleavage rupture of β phases resulted in lower cavitation erosion resistance of MAB, compared with NAB.
基金financially supported by the Youth Innovation Promotion Association(No.2014378)for Chinese Academy of Sciences。
文摘The investigate about the effect of the microstructure of Ti6Al4V alloy on its cavitation erosion and corrosion properties in marine can provide the key basis for the application.On the basis of as-received Ti6Al4V(TC4)alloy,FC-TC4 and AC-TC4 alloys were prepared by heat treatment with the cooling method of a furnace and atmospheric environment,respectively.Then the microstructure evolutions of three samples were scrutinized and the effect of microstructure on their cavitation erosion and corrosion resistance was explored.The results showed that more recrystallized grains formed as well as its content of α grains and high-angle grain boundaries increased in AC-TC4 alloy.To FC-TC4 alloy,there was obvious grain growth apart from recrystallization.Moreover,many nanotwins of Ti V and Ti Al_(3)were formed separately in FC-TC4 and AC-TC4 alloys due to the dislocation migration during heat treatment.The microstructure evolution led the hardness and elastic modulus of AC-TC4 alloy were the best,followed by FC-TC4 alloy,that of TC4 were the worst.Similarly,passivating ability of AC-TC4 alloy was the best among three samples because of its microstructure.Although cracks extended along the grain boundaries under the action of continual cavitation erosion,the passivation film formed by TiO_(2) and Al_(2)O_(3) would enhance their resistance to further corrosion and cavitation erosion in artificial seawater.
基金supported by the National Natural Science Foundation of China (No 50499336)
文摘The cavitation erosion corrosion behaviour of ZQMn12-8-3-2 manganese-nickel-aluminum bronze and ZHMn55- 3-1 manganese-brass was investigated by mass loss, electrochemical measurements （polarization curves and electrochemical impedance spectroscopy） and the cavitation damaged surfaces were observed by scanning electron microscopy （SEM）. The results showed that ZQMn12-8-3-2 had better cavitation erosion resistance than ZHMn55-3-1. After the cavitation erosion for 6 h, the cumulative mass loss of ZQMn12-8-3-2 was about 1/3 that of ZHMn55-3-1. The corrosion current density of ZQMn12-8-3-2 was less than that of ZHMn55-3-1 under both static and cavitaiton condition. The free-corrosion potentials of ZQMn12-8-3-2 and ZHMn55-3-1 were all shifted in positive direction under cavitation condition compared to static condition. In the total cumulative mass loss under cavitation condition, the pure erosion played a key role for the two tested materials （74% for ZHMn55-3-1 and 60% for ZQMn12-8-3-2）, and the total synergism between corrosion and erosion of ZQMn12-8-3-2 （39%） was larger than that of ZHMn55-3-1 （23%）. The high cavitation erosion resistance of ZQMn12-8-3-2 was mainly attributed to its lower stacking fault energy （SFE）, the higher microhardness and work-hardening ability as well as the favorable propagation of cavitation cracks for ZQMn12-8-3-2, i.e., parallel to the surface rather than perpendicular to the surface for ZHMn55-3-1.
