Effect of using monocrystalline aluminum oxide grinding wheels on the surface integrity of AISI 420 (UNS S42000) martensitic stainless steel

Abstract

Grinding is a precision machining process in which high hardness abrasive grits remove material from the workpiece in chip form with cutting, plowing and sliding interactions ensuring that appropriate surface tolerances are created. Owing to the fact that chips generated are small (due to low radial depths of cut) and that grinding wheels are poor conductors of heat, most of the heat generated is directed to the machined surface and can result in microstructural damage. Therefore, the correct selection of grinding parameters and the type of abrasive grinding wheels used in the process is essential. In this case, monocrystalline grinding grits are hard and extremely brittle compared to other alumina grits used for grinding tool and highly alloyed steels that are sensitive to burning. In this work, AISI 420 martensitic stainless steel (UNS S42000) samples were ground in order to evaluate the influence of the type of abrasive grit on surface and sub-surface integrity of workpieces. Experiments were designed and performed to screen two types of aluminum oxide grinding wheels (polycrystalline and monocrystalline), two radial depths of cut and a synthetic cutting fluid. Workpiece integrity was analyzed in terms of surface roughness parameters, R_a and R_z, microhardness and the physical analysis of ground surface texture using a scanning electron microscope (SEM). The results showed that monocrystalline abrasives provided the best results compared to conventional polycrystalline abrasive grits with the same cutting conditions in terms of surface roughness, texture, and microhardness.