THE EVALUATION OF DENSIFIED LAYER FORMATION MECHANISMS AND THICKNESS DURING DRY SLIDING WEAR OF POROUS POWDER METALLURGY PARTS

When a porous powder metallurgy part is worn by a counterbody, intense shear stresses are exerted on the surface and subsurface owing to the both normal load and tangential load (i.e. friction). Hence, the pores near the surface are closed owing to intense plastic deformation in this area and a hardened densified layer is formed. This densified layer has the thickness in which applied stresses are more than the yield stress of the matrix. In this research a porous Distaloy AE material which is a partially alloyed steel powder was worn by AISI 52100 steel in a reciprocating manner. Then subsurface stresses derived from normal and tangential load were calculated. The thickness of densified layer was obtained by comparing these stresses with yield stress of the matrix. The results compare with the metallographic photos and the differences are discussed.