A surface and sub-surface quality evaluation of three cast iron grades after grinding under various cutting conditions

Abstract

Grinding is one of the most common finishing processes used in the manufacture of metal components that require a combination of both smooth surface finish and tight tolerances. Despite the abundant knowledge concerning this process, specific literature is still scarce regarding the grinding of different cast iron grades. These materials have a wide application in the automotive industry, notably in the manufacture of gears, crankshafts, and valve control shafts. In this sense, this paper presents an experimental study of the peripheral surface grinding of three grades of cast iron grades (gray, nodular, and compacted graphite) with two SiC abrasive grinding wheels. The input variables tested were two values for depth of cut (15 and 30 mu m) and two worktable speeds (5 and 10 m/min). The output variables analyzed were surface roughness, microhardness, microstructures, and SEM images of the ground surfaces. The results showed that gray cast iron provided the best performance concerning surface and sub-surface integrity among the three cast iron grades tested, whereas the nodular cast iron exhibited both worst finishing and superficial texture. No microstructural changes were observed in the samples of gray and compacted graphite cast iron grades, irrespective of the cutting conditions investigated, unlike for the nodular cast iron grade in which microstructural change was detected. The ranking order for the grindability of the three cast iron grades in terms of roughness, microhardness and surface texture investigated in this paper is gray cast iron, compacted graphite iron and nodular cast iron.