Pore Feature and Cracking Behavior of Cold-sprayed Al-based Composite Coatings under Reciprocating Friction
Al-based composite coatings containing 30%Al2O3 were prepared on AZ31 Mg-alloy via cold-spraying technique.Then the pore feature and cracking behavior of Al-based composite coatings during reciprocating friction testing was assessed by means of a wear-testing machine,as well as and the location of crack initiation for relevant pores on the cross section of coatings.Meanwhile,models for composite coatings of elliptical-,triangular-,and rectangular-pores,and pore-free were respectively estab-lished using Abaqus and Python scripts,then the maximum stress of pores during friction and the residu-al stress on the top surface after friction were analyzed for the composite coatings.The relationship be-tween stress finite element results and the size of cracks induced by reciprocating friction was discussed.The research findings indicated that stress concentration for elliptical-,triangular-,and rectangular-pores mainly occurred at the endpoints of the major axis or at their corners during friction.From the top surface to the interface,the residual stress transformed from tensile stress to compressive stress and then back to tensile stress.For elliptical-,triangular-,and rectangular-pores,the maximum Mises stress and aver-age residual stress on the surface gradually increased.Cracks initiated and propagated from the end-points of the major axis for elliptical pores,while cracks in triangular-and rectangular-pores originated from the corners,with corresponding increases in crack length and width.Finite element analysis re-vealed that the increase in the maximum Mises stress of poresduring friction led to an increase in the av-erage residual stress on the surface after friction.This,in turn,resulted in larger crack dimensions,con-sistent with the findings from the reciprocating friction experiments.