Mechanical fastening is widely used in joining metals, particularly in automotive, aerospace, building and construction industries. However, the main concern on mechanical fastening is the issue of corrosion. An effec...Mechanical fastening is widely used in joining metals, particularly in automotive, aerospace, building and construction industries. However, the main concern on mechanical fastening is the issue of corrosion. An effective way to prolong the service life of steel fasteners is to apply protective coatings onto these components. This paper reviews and compares a few common coating deposition techniques, i.e., electroplating, hot-dip galvanizing, ion vapour deposition and mechanical plating, in terms of their characteristics. Compositional and microstructural properties including morphology and porosity, corrosion resistance performance and frictional performance of the coatings formed by each process are discussed in details. Hydrogen embrittlement, a premature failure often occurred on high strength steel fasteners, is also reviewed. The key results of recent studies of various metallic coatings on fasteners are presented to provide a fundamental understanding of the evolving topics, and the research gaps have been identified for further investigation.展开更多
The frictional performance of materials used in face seals is critical to the sealing performance.Silicon carbide is commonly used in hard rings because of its abrasion resistance,corrosion resistance,and thermal shoc...The frictional performance of materials used in face seals is critical to the sealing performance.Silicon carbide is commonly used in hard rings because of its abrasion resistance,corrosion resistance,and thermal shock resistance.In this study,the frictional performance of silicon carbide,including graphite-added silicon carbide,under water and lubrication-absent conditions was studied by using a Falex-1506 tribotester and different working parameters.In addition,the morphology of the worn surfaces was observed using scanning electron microscopy and the damage was characterized to understand the tribological behavior of different silicon carbides.The results suggest that the friction coefficients decrease with increasing pressure under water lubrication conditions because of the water within the holes on the surface of the materials.The percentage of water lubrication increases,whereas the percentage of solid friction decreases when the pressure increases.Under dry contact conditions,the friction coefficients change negligibly with increasing pressure and graphite-added silicon carbide shows better frictional performance.展开更多
The sliding friction of rock, involving all kinds of particles at the contact surface, is relevant to many problems, ranging from those in artificial engineering to earthquake dynamics. In this work, the frictional pe...The sliding friction of rock, involving all kinds of particles at the contact surface, is relevant to many problems, ranging from those in artificial engineering to earthquake dynamics. In this work, the frictional performance of the shale rock–dry quartz sand contact was investigated using a self-developed testing device. The study showed that the coefficient of friction of the contact increases with nominal stress and that the corresponding friction force increases approximately linearly with nominal stress, which is directly related to the contact stress between each single sand particle and rock shale. An overall dynamic coefficient, γ, reflecting the response of friction force to nominal stress, first decreases and then increases with area ratio, which is determined by not only the contact stress but also the interparticle friction force. These have important repercussions for a preliminary understanding of the frictional properties of the shale rock–dry quartz sand contact in hydraulic fracturing and related industrial applications.展开更多
文摘Mechanical fastening is widely used in joining metals, particularly in automotive, aerospace, building and construction industries. However, the main concern on mechanical fastening is the issue of corrosion. An effective way to prolong the service life of steel fasteners is to apply protective coatings onto these components. This paper reviews and compares a few common coating deposition techniques, i.e., electroplating, hot-dip galvanizing, ion vapour deposition and mechanical plating, in terms of their characteristics. Compositional and microstructural properties including morphology and porosity, corrosion resistance performance and frictional performance of the coatings formed by each process are discussed in details. Hydrogen embrittlement, a premature failure often occurred on high strength steel fasteners, is also reviewed. The key results of recent studies of various metallic coatings on fasteners are presented to provide a fundamental understanding of the evolving topics, and the research gaps have been identified for further investigation.
基金supported by the National Basic Rese arch Program of China(973)(Grant No.2009CB724304)the National Natural Science Foundation of China(Grant No.51275268)State Key Laboratory of Tribology(Grant No.SKLT11C4)。
文摘The frictional performance of materials used in face seals is critical to the sealing performance.Silicon carbide is commonly used in hard rings because of its abrasion resistance,corrosion resistance,and thermal shock resistance.In this study,the frictional performance of silicon carbide,including graphite-added silicon carbide,under water and lubrication-absent conditions was studied by using a Falex-1506 tribotester and different working parameters.In addition,the morphology of the worn surfaces was observed using scanning electron microscopy and the damage was characterized to understand the tribological behavior of different silicon carbides.The results suggest that the friction coefficients decrease with increasing pressure under water lubrication conditions because of the water within the holes on the surface of the materials.The percentage of water lubrication increases,whereas the percentage of solid friction decreases when the pressure increases.Under dry contact conditions,the friction coefficients change negligibly with increasing pressure and graphite-added silicon carbide shows better frictional performance.
基金Support by National Natural Science Foundation of China (No. 51575529)
文摘The sliding friction of rock, involving all kinds of particles at the contact surface, is relevant to many problems, ranging from those in artificial engineering to earthquake dynamics. In this work, the frictional performance of the shale rock–dry quartz sand contact was investigated using a self-developed testing device. The study showed that the coefficient of friction of the contact increases with nominal stress and that the corresponding friction force increases approximately linearly with nominal stress, which is directly related to the contact stress between each single sand particle and rock shale. An overall dynamic coefficient, γ, reflecting the response of friction force to nominal stress, first decreases and then increases with area ratio, which is determined by not only the contact stress but also the interparticle friction force. These have important repercussions for a preliminary understanding of the frictional properties of the shale rock–dry quartz sand contact in hydraulic fracturing and related industrial applications.
