WEAR STUDIES IN PLASTO-HYDRODYNAMIC (PHD) LUBRICATION CONDITIONS

Abstract

Understanding the tribology of the metalworking process is of importance from the point of view of energy as well as from that of material conservation. It is difficult to simulate plastic deformation conditions in the laboratory as they involve large deformation of the work piece, generating large fresh virgin surface and large heat of deformation. This usually makes the conditions too severe for the lubricant to prevent metal pick-up and wear. Keeping this in view, plastic deformation conditions were simulated on an Amsler wear testing machine, using a flat M.S. disc and a wedge shaped EN 31 disc. The effect of load, speed, cone angle and lubricant on wear were studied. The nature of M.S,.disc surface, EN 31 disc surface and the wear particles generated were examined by SEM. The metallurgical cut sections of M.S. discs were examined to study the nature of subsurface deformation using a metallurgical microscope and X-ray diffraction. The changes in the subsurface hardness was examined by a microhardness tester. It is seen that the nature of lubricant influences the nature of M.S. surface generatedr such that the surface may be from smooth to one having pitting marks. The pit may be with or without a flown boundary indicating the ductile or brittle nature of the surface. Accompanying large deformations there is also some chemical decomposition of the lubricant and also phase transformation of the surface layers. At the beginning, the size of wear particles is large and later ji reduces on the reduction of stresses due to the development conformity between the surfaces.