Effect Of Sublayer On Friction And Wear Properties Of Cralyn Composite Coating On Titanium Alloy

The hardness of the titanium alloy is low and t.he supporting force of titanium alloy is poor for hard coating,which leads to the cracking at the interface of coating/substrate of the PVD hard coating on the titanium alloy when load bearing,so the modulus of elasticity of the sublayer is the most important factor affecting bonding strength.Compared with other metal materials,the thermal conductivity and thermal expansion coefficient of titanium alloy are low.and the abrupt change of thermal stress at the the interface of coating/substrate is another factor limiting the bonding strength.Based on this,the pure Cr,pure Ti and three kinds of bimetal mixed sublayer with different Cr and Ti content were prepared by magnetron sputtering,and the CrAlYN composite coating was prepared on different sublayers.To study the effect of sublayer on the friction and wear properties of CrAlYN composite coating on titanium alloy.To discuss the selection and preparation principles of hard coating material on titanium alloy.The results show that the thickness of the five kinds of sublayer is basically the same,and the bimetal sublayer is all mechanically mixed.The clastic modulus of pure Cr sublayer is the highest,and Cr:Ti(at%)=3:1 of sublayer has the highest hardness and hard elastic ratio.The thickness of CrAl YN composite coating with different sublayers is about 2μm,while the elastic modulus,hardness and hard elastic ratio of the sublayer are positively correlated with the CrAl YN composite coating.The friction and wear tests at room temperature indicate that the friction coefficient of CrAlYN coating depends on the hardness of the sublayer.Among them,when the sublayer is Cr:Ti(at%)=3:1,the friction coefficient of the coating is the lowest The friction coefficient of pure Ti sublayer is the highest.After annealing at 400℃,the coating strength keeps a stable state,except for a slight decrease in the bonding strength of the coating.The friction coefficient of the coating depends on the hardness and the coefficient of thermal expansion of the sublayer,in which the influence of the hardness of the sublayer is the same as the friction and wear at room temperature.The phase composition of the coating is not changed after the thermal shock at 400℃.The friction coefficient of the coating depends mainly on the matching degree of the thermal expansion coefficient between the sublayer and the substrate after the heat shock.When the sublayer is Cr:Ti(at%)=3:1,the thermal expansion coefficient of the sublayer is the most matched to the matrix,and the friction coefficient of the coating is the lowest.The pure Ti sublayer has the lowest lattice missmatch with matrix,but the CrAlYN coating has the highest friction coefficient.For TC4 titanium alloy,the hardness of the sublayer coating is the main factor affecting the tribological properties of PVD hard coating.When the hardness is close,the bonding strength depends on the matching between the sublayer and the thermal expansion coefficient of the TC4 matrix.If the heat effect is larger in the friction and wear environment,the thermal expansion coefficient of the sublayer is the main factor determining the tribological properties of the PVD composite coating on the titanium alloy.