In electroplating lines,many conductor rolls are installed in electroplating bath.Typical electroplatings are tin plating(ETL) and zinc plating(EGL),and from required product qualities,a vertical cell for the former a...In electroplating lines,many conductor rolls are installed in electroplating bath.Typical electroplatings are tin plating(ETL) and zinc plating(EGL),and from required product qualities,a vertical cell for the former and a horizontal cell for the latter is often used.Generally,chrome plating or WC cermet thermal spray coating is applied to stainless steel conductor roll in ETL for prolonging service life by improvement of wear resistance and corrosion resistance.On the other hand,Hastelloy type alloy substrate is used for conductor rolls in EGL due to severe corrosion environment of electro plating solution.Thermal spray coating is effective for reducing wear,but there are many cases where the coating cannot complete expected service life when corrosion becomes an issue.In this study,thermal spray coating for ETL conductor roll and development of the coating for EGL conductor roll to meet expected service life are described.展开更多
In cases of decorative and functional applications, chromium results in protection against wear and corrosion combined with chemical resistance and good lubricity. However, pressure to identify alternatives or to impr...In cases of decorative and functional applications, chromium results in protection against wear and corrosion combined with chemical resistance and good lubricity. However, pressure to identify alternatives or to improve conventional chromium electroplating mechanical characteristics has increased in recent years, related to the reduction in the fatigue strength of the base material and to environmental requirements (1). In the present study plasma sprayed coatings (aluminum oxide, Co-28Mo-8Cr-2Si, tungsten carbide, chrome carbide) and electrolytic hard chrome coatings abrasive wear properties have been compared. The wear tests were conducted with a Taber abraser, at room temperature.展开更多
Thermal barrier coating (TBC) revolutionized the industry by allowing higher operating temperatures for equipment, such as gas turbines in the aeronautical industry. However, at high temperatures, the TBC is exposed t...Thermal barrier coating (TBC) revolutionized the industry by allowing higher operating temperatures for equipment, such as gas turbines in the aeronautical industry. However, at high temperatures, the TBC is exposed to the attack of molten silicates, known as CMAS (Calcium-Magnesium-Alumino-Silicate), which are particles from the environment that infiltrate the TBC, causing delamination. In this study, samples coated with TBC by thermal spray and covered with CMAS were evaluated at temperatures of 1200˚C and 1250˚C. For each temperature, exposure times of 1 h and 5 h were used. Samples with longer exposure time had a considerable volume increase. The main contribution of this work was to demonstrate the non-wettability of the CMAS, even in the 5-h heat treatments, which prevented its infiltration in the deeper regions. The conditions to guarantee the formation of the silicate and its consequent wettability are also discussed.展开更多
Bioactive thermal spray coatings produced via high-velocity oxygen fuel spray(HVOF)from hydroxyapatite(HAp)and bioactive glasses(BG)have the potential to be employed on temporary implants due to the ability of both HA...Bioactive thermal spray coatings produced via high-velocity oxygen fuel spray(HVOF)from hydroxyapatite(HAp)and bioactive glasses(BG)have the potential to be employed on temporary implants due to the ability of both HAp and BG to dissolve and promote osseointegration,considering that both phases have different reaction and dissolution rates under in-vitro conditions.In the present work,75%wt.HAp-25%wt.S53P4 bioactive glass powders were HVOF-sprayed to obtain HAp/S53P4 BG composite coatings on a bioresorbable AZ31 alloy.The study is focused on exploring the effect of the stand-off distance and fuel/oxygen ratio variation as HVOF parameters to obtain stable structural coatings and to establish their effect on the phases and microstructure produced in those coatings.Different characterization techniques,such as scanning electron microscopy,X-ray diffraction,and Fourier transform infrared spectroscopy,were employed to characterize relevant structural and microstructural properties of the composite coatings.The results showed that thermal gradients during coating deposition must be managed to avoid delamination due to the high temperature achieved(max 550℃)and the differences in coefficients of thermal expansion.It was also found that both spraying distance and oxygen/fuel ratio allowed to keep the hydroxyapatite as the main phase in the coatings.In addition,in-vitro electrochemical studies were performed on the obtained HAp/S53P4 BG composite coatings and compared against the uncoated AZ31 alloy.The results showed a significant decrease in hydrogen evolution(at least 98%)when the bioactive coating was applied on the Mg alloy during evaluation in simulated body fluid(SBF).展开更多
An investigation of Fe-doping effect on SnO_(2) thin films was performed in this study using thermal spray pyrolysis(TSP) method.The surface morphology and structural,optical and electrical properties were studied by ...An investigation of Fe-doping effect on SnO_(2) thin films was performed in this study using thermal spray pyrolysis(TSP) method.The surface morphology and structural,optical and electrical properties were studied by field energy scanning electron microscope(FESEM),X-ray diffraction(XRD),ultraviolet-visible(UV-Vis) spectroscopy and four-point probe method.FES EM images demonstrate that the surface morphology of the as-deposited films varies when Fe-doping content varies.XRD studies reveal that crystallite size and preferential growth orientations of the films are dependent on Fe-doping concentrations.The grain size is found to decrease with the increase in Fe content.These studies also specify that the films have tetragonal rutile-type structure with mixed secondary phases.The texture coefficient value of(110) plane increases with the concomitant in-plane(220) decrease in higher doping concentrations.The resistivity and the optical absorbance are found to increase with Fe concentration.The direct optical band gap decreases from 3.94 to3.52 eV with increasing Fe content.展开更多
Potential engineering applications of magnesium(Mg)and Mg-based alloys,as the lightest structural metal,have made them a popular subject of study.However,the inferior corrosion and wear characteristics significantly l...Potential engineering applications of magnesium(Mg)and Mg-based alloys,as the lightest structural metal,have made them a popular subject of study.However,the inferior corrosion and wear characteristics significantly limit their application range.It is widely recognized that surface treatment is the most commonly utilized technique for remarkably improving a substrate’s surface characteristics.Numerous methods have been introduced for the surface treatment of Mg and Mg-based alloys to improve their corrosion behavior and tribological performance.Among these,thermal spray(TS)technology provides several methods for deposition of various functional metallic,ceramic,cermet,or other coatings tailored to particular conditions.Recent researches have shown the tremendous potential for thermal spray coated Mg alloys for biomedical and industrial applications.In this context,the cold spray(CS)method,as a comparatively new TS coating technique,can generate the coating layer using kinetic energy rather than combined thermal and kinetic energies,like the high-velocity oxy-fuel(HVOF)spray method.Moreover,the CS process,as a revolutionary method,is able to repair and refurbish with a faster turnaround time;it also provides solutions that do not require dealing with the thermal stresses that are part of the other repair processes,such as welding or other TS processes using a high-temperature flame.In this review paper,the recently designed coatings that are specifically applied to Mg alloys(primarily for industrial applications)employing various coating processes are reviewed.Because of the increased utilization of CS technology for both 3D printed(additively manufactured)coatings and repair of structurally critical components,the most recent CS methods for the surface treatment,repair,and refurbishment of Mg alloys as well as their benefits and restrictions are then discussed and reviewed in detail.Lastly,the prospects of this field of study are briefly discussed,along with a summary of the presented work.展开更多
The present paper deals with the investigation of microstructure and high-temperature hot corrosion behavior of high-velocity oxy fuel(HVOF)-produced coatings. Two powder coating compositions, namely, Ni22Cr10Al1Y all...The present paper deals with the investigation of microstructure and high-temperature hot corrosion behavior of high-velocity oxy fuel(HVOF)-produced coatings. Two powder coating compositions, namely, Ni22Cr10Al1Y alloy powder and Ni22Cr10Al1Y(80 wt%;microsized)–silicon carbide(SiC)(20 wt%;nano(N)) powder, were deposited on a T-22 boiler tube steel. The hot corrosion behavior of bare and coated steels was tested at 900°C for 50 cycles in Na2SO4–60 wt%V2O5 molten-salt environment. The kinetics of corrosion was established with weight change measurements after each cycle. The microporosity and microhardness of the as-coated samples have been reported. The X-ray diffraction,field emission-scanning electron microscopy/energy dispersive spectroscopy, and X-ray mapping characterization techniques have been utilized for structural analysis of the as-coated and hot-corroded samples. The results showed that both coatings were deposited with a porosity less than2%. Both coated samples revealed the development of harder surfaces than the substrate. During hot corrosion testing, the bare T22 steel showed an accelerated corrosion in comparison with its coated counterparts. The HVOF-sprayed coatings were befitted effectively by maintaining their adherence during testing. The Ni22Cr10Al1Y–20 wt%SiC(N) composite coating was more effective than the Ni–22Cr–10Al–1Y coating against corrosion in the high-temperature fluxing process.展开更多
The self-lubricating ceramic coatings that can control friction and wear have attracted researchers’widespread attention.However,the poor interfacial bonding between lubricants and ceramics and the deterioration of m...The self-lubricating ceramic coatings that can control friction and wear have attracted researchers’widespread attention.However,the poor interfacial bonding between lubricants and ceramics and the deterioration of mechanical properties due to a tribological design limit their practical applications.Here,a robust self-lubricating coating was fabricated by an in-situ synthesis of MoS_(2)/C within inherent defects of thermally sprayed yttria-stabilized zirconia(YSZ)coatings.The edge-pinning by noncoherent endows hybrid coatings with excellent interfacial strength,increasing their hardness(HV)and cohesive strength.Furthermore,owing to the formation of a well-covered robust lubricating film at a frictional interface,a coefficient of friction(COF)can be reduced by 79.6%to 0.15,and a specific wear rate(W)drops from 1.36×10^(−3) to 6.27×10^(−7) mm^(3)·N^(−1)·m^(−1).Combining outstanding mechanical properties and tribological performance,the hybrid coating exhibits great application potential in controlling friction and wear.Importantly,this strategy of introducing the target materials into the inherent defects of the raw materials to improve the relevant properties opens new avenues for the design and preparation of composite materials.展开更多
The primary focus during surgery is to ensure successful implantation by achieving long-term and stable fixation of implants.Orthopaedic surgery is now more focused on the development of novel biomaterials intended to...The primary focus during surgery is to ensure successful implantation by achieving long-term and stable fixation of implants.Orthopaedic surgery is now more focused on the development of novel biomaterials intended to improve implant performance.To obtain a better understanding of metal implants,this article investigated the causes of material failures in certain cases and analysed a few case studies.The interaction between the implant and bone tissue was a crucial aspect of successful implantation,and this study explored the factors influencing this interaction as well as ways to improve it.Several modern approaches used for modifying implant surfaces were systematically illustrated and briefly analysed.Thermal spray coatings were often favoured because of their wide range of coating materials,but other substantial surface modifications(such as friction stir processing and laser surface texturing)were also used for a selection of applications.Notably,implant surfaces with desirable features,such as biocompatibility,antibacterial properties,corrosion resistance,and wear resistance,were essential for optimising implant functionality.This systematic review's main aim is to provide exhaustive reference information and a broad overview to advance the production and design of orthopaedic implants.展开更多
文摘In electroplating lines,many conductor rolls are installed in electroplating bath.Typical electroplatings are tin plating(ETL) and zinc plating(EGL),and from required product qualities,a vertical cell for the former and a horizontal cell for the latter is often used.Generally,chrome plating or WC cermet thermal spray coating is applied to stainless steel conductor roll in ETL for prolonging service life by improvement of wear resistance and corrosion resistance.On the other hand,Hastelloy type alloy substrate is used for conductor rolls in EGL due to severe corrosion environment of electro plating solution.Thermal spray coating is effective for reducing wear,but there are many cases where the coating cannot complete expected service life when corrosion becomes an issue.In this study,thermal spray coating for ETL conductor roll and development of the coating for EGL conductor roll to meet expected service life are described.
文摘In cases of decorative and functional applications, chromium results in protection against wear and corrosion combined with chemical resistance and good lubricity. However, pressure to identify alternatives or to improve conventional chromium electroplating mechanical characteristics has increased in recent years, related to the reduction in the fatigue strength of the base material and to environmental requirements (1). In the present study plasma sprayed coatings (aluminum oxide, Co-28Mo-8Cr-2Si, tungsten carbide, chrome carbide) and electrolytic hard chrome coatings abrasive wear properties have been compared. The wear tests were conducted with a Taber abraser, at room temperature.
文摘Thermal barrier coating (TBC) revolutionized the industry by allowing higher operating temperatures for equipment, such as gas turbines in the aeronautical industry. However, at high temperatures, the TBC is exposed to the attack of molten silicates, known as CMAS (Calcium-Magnesium-Alumino-Silicate), which are particles from the environment that infiltrate the TBC, causing delamination. In this study, samples coated with TBC by thermal spray and covered with CMAS were evaluated at temperatures of 1200˚C and 1250˚C. For each temperature, exposure times of 1 h and 5 h were used. Samples with longer exposure time had a considerable volume increase. The main contribution of this work was to demonstrate the non-wettability of the CMAS, even in the 5-h heat treatments, which prevented its infiltration in the deeper regions. The conditions to guarantee the formation of the silicate and its consequent wettability are also discussed.
基金the National Council of Humanities,Science,and Technology(CONAHCYT)through the"Investigadores por Mexico"program,projects 848 and 881。
文摘Bioactive thermal spray coatings produced via high-velocity oxygen fuel spray(HVOF)from hydroxyapatite(HAp)and bioactive glasses(BG)have the potential to be employed on temporary implants due to the ability of both HAp and BG to dissolve and promote osseointegration,considering that both phases have different reaction and dissolution rates under in-vitro conditions.In the present work,75%wt.HAp-25%wt.S53P4 bioactive glass powders were HVOF-sprayed to obtain HAp/S53P4 BG composite coatings on a bioresorbable AZ31 alloy.The study is focused on exploring the effect of the stand-off distance and fuel/oxygen ratio variation as HVOF parameters to obtain stable structural coatings and to establish their effect on the phases and microstructure produced in those coatings.Different characterization techniques,such as scanning electron microscopy,X-ray diffraction,and Fourier transform infrared spectroscopy,were employed to characterize relevant structural and microstructural properties of the composite coatings.The results showed that thermal gradients during coating deposition must be managed to avoid delamination due to the high temperature achieved(max 550℃)and the differences in coefficients of thermal expansion.It was also found that both spraying distance and oxygen/fuel ratio allowed to keep the hydroxyapatite as the main phase in the coatings.In addition,in-vitro electrochemical studies were performed on the obtained HAp/S53P4 BG composite coatings and compared against the uncoated AZ31 alloy.The results showed a significant decrease in hydrogen evolution(at least 98%)when the bioactive coating was applied on the Mg alloy during evaluation in simulated body fluid(SBF).
文摘An investigation of Fe-doping effect on SnO_(2) thin films was performed in this study using thermal spray pyrolysis(TSP) method.The surface morphology and structural,optical and electrical properties were studied by field energy scanning electron microscope(FESEM),X-ray diffraction(XRD),ultraviolet-visible(UV-Vis) spectroscopy and four-point probe method.FES EM images demonstrate that the surface morphology of the as-deposited films varies when Fe-doping content varies.XRD studies reveal that crystallite size and preferential growth orientations of the films are dependent on Fe-doping concentrations.The grain size is found to decrease with the increase in Fe content.These studies also specify that the films have tetragonal rutile-type structure with mixed secondary phases.The texture coefficient value of(110) plane increases with the concomitant in-plane(220) decrease in higher doping concentrations.The resistivity and the optical absorbance are found to increase with Fe concentration.The direct optical band gap decreases from 3.94 to3.52 eV with increasing Fe content.
文摘Potential engineering applications of magnesium(Mg)and Mg-based alloys,as the lightest structural metal,have made them a popular subject of study.However,the inferior corrosion and wear characteristics significantly limit their application range.It is widely recognized that surface treatment is the most commonly utilized technique for remarkably improving a substrate’s surface characteristics.Numerous methods have been introduced for the surface treatment of Mg and Mg-based alloys to improve their corrosion behavior and tribological performance.Among these,thermal spray(TS)technology provides several methods for deposition of various functional metallic,ceramic,cermet,or other coatings tailored to particular conditions.Recent researches have shown the tremendous potential for thermal spray coated Mg alloys for biomedical and industrial applications.In this context,the cold spray(CS)method,as a comparatively new TS coating technique,can generate the coating layer using kinetic energy rather than combined thermal and kinetic energies,like the high-velocity oxy-fuel(HVOF)spray method.Moreover,the CS process,as a revolutionary method,is able to repair and refurbish with a faster turnaround time;it also provides solutions that do not require dealing with the thermal stresses that are part of the other repair processes,such as welding or other TS processes using a high-temperature flame.In this review paper,the recently designed coatings that are specifically applied to Mg alloys(primarily for industrial applications)employing various coating processes are reviewed.Because of the increased utilization of CS technology for both 3D printed(additively manufactured)coatings and repair of structurally critical components,the most recent CS methods for the surface treatment,repair,and refurbishment of Mg alloys as well as their benefits and restrictions are then discussed and reviewed in detail.Lastly,the prospects of this field of study are briefly discussed,along with a summary of the presented work.
基金DST,New Delhi for their research grant(No.SB/FTP/ETA-435/2012,Dated-10/6/2013)that funded the research and development of the project entitled“Nano-composite Coatings to Control Erosion of Boiler Tubes of Steam Generating Plants.”
文摘The present paper deals with the investigation of microstructure and high-temperature hot corrosion behavior of high-velocity oxy fuel(HVOF)-produced coatings. Two powder coating compositions, namely, Ni22Cr10Al1Y alloy powder and Ni22Cr10Al1Y(80 wt%;microsized)–silicon carbide(SiC)(20 wt%;nano(N)) powder, were deposited on a T-22 boiler tube steel. The hot corrosion behavior of bare and coated steels was tested at 900°C for 50 cycles in Na2SO4–60 wt%V2O5 molten-salt environment. The kinetics of corrosion was established with weight change measurements after each cycle. The microporosity and microhardness of the as-coated samples have been reported. The X-ray diffraction,field emission-scanning electron microscopy/energy dispersive spectroscopy, and X-ray mapping characterization techniques have been utilized for structural analysis of the as-coated and hot-corroded samples. The results showed that both coatings were deposited with a porosity less than2%. Both coated samples revealed the development of harder surfaces than the substrate. During hot corrosion testing, the bare T22 steel showed an accelerated corrosion in comparison with its coated counterparts. The HVOF-sprayed coatings were befitted effectively by maintaining their adherence during testing. The Ni22Cr10Al1Y–20 wt%SiC(N) composite coating was more effective than the Ni–22Cr–10Al–1Y coating against corrosion in the high-temperature fluxing process.
基金support from the National Natural Science Foundation of China (51905212)Guangdong Key Laboratory of Modern Surface Engineering Technology (2020B1212060049)+2 种基金Science and Technology Project of Guangdong Academy (2021GDASYL-20210103062)Young Scientific and Technological Talents Promotion Project of Guangzhou Science and Technology Association (X20210201061)Foshan Taoyuan Institute of Advanced Manufacturing (TYKF202203003).
文摘The self-lubricating ceramic coatings that can control friction and wear have attracted researchers’widespread attention.However,the poor interfacial bonding between lubricants and ceramics and the deterioration of mechanical properties due to a tribological design limit their practical applications.Here,a robust self-lubricating coating was fabricated by an in-situ synthesis of MoS_(2)/C within inherent defects of thermally sprayed yttria-stabilized zirconia(YSZ)coatings.The edge-pinning by noncoherent endows hybrid coatings with excellent interfacial strength,increasing their hardness(HV)and cohesive strength.Furthermore,owing to the formation of a well-covered robust lubricating film at a frictional interface,a coefficient of friction(COF)can be reduced by 79.6%to 0.15,and a specific wear rate(W)drops from 1.36×10^(−3) to 6.27×10^(−7) mm^(3)·N^(−1)·m^(−1).Combining outstanding mechanical properties and tribological performance,the hybrid coating exhibits great application potential in controlling friction and wear.Importantly,this strategy of introducing the target materials into the inherent defects of the raw materials to improve the relevant properties opens new avenues for the design and preparation of composite materials.
基金J Sharath Kumar thanks to Ministry of Education,Government of India for the research scholarship.
文摘The primary focus during surgery is to ensure successful implantation by achieving long-term and stable fixation of implants.Orthopaedic surgery is now more focused on the development of novel biomaterials intended to improve implant performance.To obtain a better understanding of metal implants,this article investigated the causes of material failures in certain cases and analysed a few case studies.The interaction between the implant and bone tissue was a crucial aspect of successful implantation,and this study explored the factors influencing this interaction as well as ways to improve it.Several modern approaches used for modifying implant surfaces were systematically illustrated and briefly analysed.Thermal spray coatings were often favoured because of their wide range of coating materials,but other substantial surface modifications(such as friction stir processing and laser surface texturing)were also used for a selection of applications.Notably,implant surfaces with desirable features,such as biocompatibility,antibacterial properties,corrosion resistance,and wear resistance,were essential for optimising implant functionality.This systematic review's main aim is to provide exhaustive reference information and a broad overview to advance the production and design of orthopaedic implants.
