Influence Of Stress On Corrosion And Wear Behavior Of Carbidic Austempered Ductile Iron

Carbidic austempered ductile iron?CADI?balls generate complex residual stresses during manufacture and service process,which has a significant effect on wear and corrosion of CADI balls.However the influence of residual stress on CADI grinding ball has not been systematically studied at domestic and abroad.This paper first studied the stress state during production and service of CADI grinding ball.Then a unidirectional compressive stress loading device was designed to test corrosive and wear behavior of CADI materials under compressive stress.Single-scratch method was used to study the wear performance of CADI materials under different pre-stress conditions and the effects of stress on the corrosion behavior of CADI materials were explored by static immersion corrosion and electrochemical corrosion methods.It will provide a valuable reference for effectively improving the corrosion and wear performance of CADI materials,and for further understanding the influencing factors and mechanisms of corrosion and wear behavior.The results show that:?1?With the austempering temperature increases from 200?to 260?,the thermal stress of the surface of the ball is increased as the compressive stress.However,the transformation stress on the CADI grinding ball surface was tensile stress,which leads to the stress of surface of CADI grinding balls gradually decreases from the original compressive stress to the tensile stress when austempered at 200??2?After serving for a period of time under actual working conditions,mechanical stress caused by non-uniform deformation and transformation induced by martensitic transformation are all compressive stress and quite large up to about 600 MPa on the surface of CADI grinding ball.?3?In the scratch test,the applied pre-stress has no effect on the second principal stress??₂?,and the third principal stress??₃?is always compressive.With the increasing of pre-stress,the first principal stress??₁?gradually decreases from the original tensile stress to the compressive stress,and the maximum shear stress(?_max)decreased gradually.?4?With the pre-stress increases from 0 MPa to 900 MPa,the width of the scratches decreases,cracks in carbides reduce,material damage and reduction of removal rate reduces.It indicates that the existence of compressive stress can improve the wear resistance of CADI materials.With the increase of normal load,the width of scratch increases,and the volume of material removal increases.The ability to resist abrasive wear is reduced.?5?With the increase of pre-stress,the corrosion resistance of CADI material decreases.Moreover,compressive stress can cause stress corrosion cracking of CADI materials in corrosive medium,and its mechanism is the anode active channel dissolves.With the increase of the pre-pressure,the corrosion rate increases,and the external stress can accelerate the corrosion process,and the corrosion rate of CADI material under pre-stress stress condition is linear with the corrosion rate of material under no-stress stress.