基体材料力学性能对316L不锈钢颗粒沉积行为的影响

INFLUENCE OF SUBSTRATE MECHANICAL PROPERTIES ON DEPOSITION BEHAVIOUR OF 316L STAINLESS STEEL POWDER

研究了基体材料的力学性能对冷喷涂316L不锈钢单颗粒沉积行为的影响.结果表明,除硬度之外,弹性模量和Poisson比也会影响颗粒的沉积行为.这是由于基体性质对颗粒/基体的能量分配和结合机制造成了影响.其中,沉积颗粒的变形行为与颗粒吸收的能量有关,而沉积效率与基体吸收的能量及结合机制有关.根据沉积颗粒的变形行为,将基体分为2类:颗粒几乎不变形,此时基体的硬度和弹性模量皆低于颗粒材料,颗粒与基体的结合主要是机械咬合,推导出可用于推断相同颗粒在基体上沉积趋势的参数E_(para),并以AZ91镁合金为基体进行验证;颗粒发生强烈变形,此时基体的硬度或弹性模量高于颗粒材料,结合机制更为复杂,此时增加颗粒/基体新鲜表面接触面积有利于提高沉积效率.

Nowadays the theory of critical velocity of particles in cold spray has been already accepted gen- erally. In the familiar semi- empirical formulas of the theory, only the properties and conditions of particles have been considered but there is no consideration of substrate. Yet most researches for effect of substrates＇ properties implied hardness of substrate was the most essential. However, little attention has been devoted to influence of other mechanical properties （e.g. Young＇s modulus and Poisson＇s ratio） and their cooperation on the deposition behavior. In order to study the effect systematically, 316L stainless steel particles were deposited by wipe test on six different substrates with a widely range of mechanical properties including Young＇s modulus, hardness and Poisson＇s ratio. They are pure Al, pure Cu, 7075T6 Al alloy, mild steel, Inconel625 and Ti6Al4V. The specimens have been investigated from morphology, cross-section and deposition efficiency. It is found that not only hardness but also Young＇s modulus and Poisson＇s ratio can affect deformation and deposition of bonded particles through playing arole in energy partition and bonding mechanism. In the case, the deformation of deposited particles is dependent on energy accepted by the particles, while the deposition efficiency is related to the bonding mechanism and energy ac- cepted by substrate. According to the deformation level of the deposited particles, there are two kinds of substrate materials. On the one hand, bonding between particles with little deformation and their substrates is mainly depen- dent on mechanical interlock, in which both hardness and Young＇s modulus of the substrates are lower than that of the particle. Then a parameter, Epara, has been calculated to predict the tendency of deposition efficiency for the situa- tions. AZ91 alloy has been employed as substrate material in confirmatory experiment. Its result indicates that Epara, is available for tendency prediction of the deposition efficiency of spherical-like deposited particle. On the other hand, the bonding mechanism of deposited particle with obviously flattening is more complex. In this situation, ei- ther hardness or Young＇s modulus of the substrates is higher than that of the particle. The more area of fresh metal contacts on the interface, the higher deposition efficiency is.