Grinding of hardened steel for tribological performance
Abstract
The use of super-abrasives such as cubic boron nitride (CBN) in the grinding of hardened steels shows promise for improving the performance of today's engineering surfaces. Tribological performance of a ground surface is determined by surface roughness, hardness, near-surface microstructure, and residual stress. In combination, these four characteristics are referred to as surface integrity throughout this document. Hardened specimens of 52100 and M50 steels are plunge ground with CBN grinding wheels, and for comparison, conventional aluminum oxide wheels. When combined with the workpiece velocity, the material removal rate is obtained from the measured depth and width of each cut. The grinding forces, normal and tangential, are measured using a dynamometer. Grinding forces are shown to be proportional to material removal rate over a range of grinding parameters so that the specific energy required to remove a given volume of material is constant. The work/wheel interface is characterized through measurement of the grinding contact stiffness. A procedure for efficient parameter studies, "ramp grinding", is proposed and validated. The ground surface is evaluated through measurement of surface roughness, hardness, near surface residual stress, and microstructure. It is shown that surface roughness is virtually independent of material removal rate. A remarkable correlation is found between bulk grinding surface temperature, residual stress and workpiece burn. Thus, bulk grinding temperature is established as the parameter most important to surface integrity. The superior performance of CBN over aluminum oxide abrasives is shown to be due to the thermal properties of CBN.
Degree
Ph.D.
Advisors
Farris, Purdue University.
Subject Area
Mechanics|Industrial engineering|Mechanical engineering
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