Titanium alloys are excellent structural materials in engineering fields,but their poor tribological properties limit their further applications.Electroless plating is an effective method to enhance the tribological p...Titanium alloys are excellent structural materials in engineering fields,but their poor tribological properties limit their further applications.Electroless plating is an effective method to enhance the tribological performance of alloys,but it is difficult to efficiently apply to titanium alloys,due to titanium alloy’s strong chemical activity.In this work,the electroless Nickel-Boron(Ni-B)coating was successfully deposited on the surface of titanium alloy(Ti-6AL-4V)via a new pre-treatment process.Then,linearly reciprocating sliding wear tests were performed to evaluate the tribological behaviors of titanium alloy and its electroless Ni-B coatings.It was found that the Ni-B coatings can decrease the wear rate of the titanium alloy from 19.89×10^(−3)mm^(3)to 0.41×10^(−3)mm^(3),which attributes to the much higher hardness of Ni-B coatings.After heat treatment,the hardness of Ni-B coating further increases corresponding to coating crystallization and hard phase formation.However,heat treatment does not improve the tribological performance of Ni-B coating,due to the fact that higher brittleness and more severe oxidative wear exacerbate the damage of heat-treated coatings.Furthermore,the Ni-B coatings heat-treated both in air and nitrogen almost present the same tribological performance.The finding of this work on electroless coating would further extend the practical applications of titanium alloys in the engineering fields.展开更多
Processing(grinding,polishing)of phosphate laser(PL)glass involves material removal at two vastly different(spatial)scales.In this study,the nano‐and macro‐tribological properties of PL glass are investigated by rub...Processing(grinding,polishing)of phosphate laser(PL)glass involves material removal at two vastly different(spatial)scales.In this study,the nano‐and macro‐tribological properties of PL glass are investigated by rubbing the glass against a SiO_(2) counter‐surface in both dry and humid conditions.The results indicate that the friction of the PL glass/SiO_(2) pair has opposing trends at the nano‐and macroscales.At the nanoscale,the friction coefficient(COF)in humid air is much higher than in dry air,which is attributed to the capillary effect of the absorbed water‐film at the interface.At the macroscale,on the other hand,the COF in humid air is lower than in dry air,because the water‐related mechanochemical wear makes the worn surface less susceptible to cracking.Material removal for PL glass is better facilitated by humid air than by dry air at both scales,because the stress‐enhanced hydrolysis accelerates the material‐removal process in glass.Moreover,the material‐removal is more sensitive to contact pressure at the macroscale,because stronger mechanical‐interaction occurs during material removal at the macroscale with the multi asperity contact mode.At the macroscale,the material removal is more sensitive to contact pressure in humid air compared to dry air.Because almost all mechanical energy is used to remove material in humid air,and most of the mechanical energy is used to produce cracks in PL glass in dry air.The results of this study can help optimize the multi‐scale surface processing of optical glasses.展开更多
Tribology behaviors of energetic crystals play critical roles in the friction-induced hotspot in highenergy explosive,however,the binder and energetic crystals are not distinguished properly in previous investigations...Tribology behaviors of energetic crystals play critical roles in the friction-induced hotspot in highenergy explosive,however,the binder and energetic crystals are not distinguished properly in previous investigations.In this study,for the first time,the nanoscale friction ofβ-octahydro-1,3,5,7-tetranitro1,3,5,7-tetrazocine(β-HMX)crystal is studied with nanoscratch tests under the ramping load mode.The results show that the nanoscale friction and wear ofβ-HMX crystal,as a typical energetic material,is highly depended on the applied load.The friction coefficient ofβ-HMX crystal is initially high when no discernible wear is observed,and then it decreases to a stable value which varies from~0.2 to~0.7,depending on the applied load,scratch direction,and crystal planes.Theβ-HMX(011)surfaces show weakly friction and wear anisotropy behavior;in contrast,theβ-HMX(110)surfaces show strongly friction and wear anisotropy behavior where the friction coefficient,critical load for the elastic–plastic deformation transition and plastic–cracking deformation transition,and deformation index at higher normal load are highly depended on the scratch directions.Further analyses indicate the slip system and direction ofβ-HMX surfaces play key roles in determining the nanoscale friction and wear ofβ-HMX surfaces.The obtained results can provide deeper insight into the friction and wear of energetic crystal materials.展开更多
基金Supported by Sichuan Provincial Science and Technology Program of China(Grant No.2018JY0245)National Natural Science Foundation of China(Grant No.51975492)Natural Science Foundation of Southwest University of Science and Technology of China(Grant No.19xz7163).
文摘Titanium alloys are excellent structural materials in engineering fields,but their poor tribological properties limit their further applications.Electroless plating is an effective method to enhance the tribological performance of alloys,but it is difficult to efficiently apply to titanium alloys,due to titanium alloy’s strong chemical activity.In this work,the electroless Nickel-Boron(Ni-B)coating was successfully deposited on the surface of titanium alloy(Ti-6AL-4V)via a new pre-treatment process.Then,linearly reciprocating sliding wear tests were performed to evaluate the tribological behaviors of titanium alloy and its electroless Ni-B coatings.It was found that the Ni-B coatings can decrease the wear rate of the titanium alloy from 19.89×10^(−3)mm^(3)to 0.41×10^(−3)mm^(3),which attributes to the much higher hardness of Ni-B coatings.After heat treatment,the hardness of Ni-B coating further increases corresponding to coating crystallization and hard phase formation.However,heat treatment does not improve the tribological performance of Ni-B coating,due to the fact that higher brittleness and more severe oxidative wear exacerbate the damage of heat-treated coatings.Furthermore,the Ni-B coatings heat-treated both in air and nitrogen almost present the same tribological performance.The finding of this work on electroless coating would further extend the practical applications of titanium alloys in the engineering fields.
基金The authors are grateful for financial support from the National Natural Science Foundation of China(Nos.51975492 and 51575462)the Scientific Research Fund of Sichuan Provincial Education Department,China(18ZA0504)+3 种基金the Research Fund Supported by Sichuan Science and Technology Program(2018JY0245)the Research Foundation of Southwest University of Science and Technology(18zx7162)the Tribology Science Fund of State Key Laboratory of Tribology(SKLTKF19B15)the Project National United Engineering Laboratory for Advanced Bearing Tribology,Henan University of Science and Technology(201910).
文摘Processing(grinding,polishing)of phosphate laser(PL)glass involves material removal at two vastly different(spatial)scales.In this study,the nano‐and macro‐tribological properties of PL glass are investigated by rubbing the glass against a SiO_(2) counter‐surface in both dry and humid conditions.The results indicate that the friction of the PL glass/SiO_(2) pair has opposing trends at the nano‐and macroscales.At the nanoscale,the friction coefficient(COF)in humid air is much higher than in dry air,which is attributed to the capillary effect of the absorbed water‐film at the interface.At the macroscale,on the other hand,the COF in humid air is lower than in dry air,because the water‐related mechanochemical wear makes the worn surface less susceptible to cracking.Material removal for PL glass is better facilitated by humid air than by dry air at both scales,because the stress‐enhanced hydrolysis accelerates the material‐removal process in glass.Moreover,the material‐removal is more sensitive to contact pressure at the macroscale,because stronger mechanical‐interaction occurs during material removal at the macroscale with the multi asperity contact mode.At the macroscale,the material removal is more sensitive to contact pressure in humid air compared to dry air.Because almost all mechanical energy is used to remove material in humid air,and most of the mechanical energy is used to produce cracks in PL glass in dry air.The results of this study can help optimize the multi‐scale surface processing of optical glasses.
基金The authors gratefully acknowledge the financial support of this work by President Foundation of China Academy of Engineering Physics(YZJJLX2020005)National Natural Science Foundation of China(Grant No.51975492)。
文摘Tribology behaviors of energetic crystals play critical roles in the friction-induced hotspot in highenergy explosive,however,the binder and energetic crystals are not distinguished properly in previous investigations.In this study,for the first time,the nanoscale friction ofβ-octahydro-1,3,5,7-tetranitro1,3,5,7-tetrazocine(β-HMX)crystal is studied with nanoscratch tests under the ramping load mode.The results show that the nanoscale friction and wear ofβ-HMX crystal,as a typical energetic material,is highly depended on the applied load.The friction coefficient ofβ-HMX crystal is initially high when no discernible wear is observed,and then it decreases to a stable value which varies from~0.2 to~0.7,depending on the applied load,scratch direction,and crystal planes.Theβ-HMX(011)surfaces show weakly friction and wear anisotropy behavior;in contrast,theβ-HMX(110)surfaces show strongly friction and wear anisotropy behavior where the friction coefficient,critical load for the elastic–plastic deformation transition and plastic–cracking deformation transition,and deformation index at higher normal load are highly depended on the scratch directions.Further analyses indicate the slip system and direction ofβ-HMX surfaces play key roles in determining the nanoscale friction and wear ofβ-HMX surfaces.The obtained results can provide deeper insight into the friction and wear of energetic crystal materials.
