SURFACE AND SUBSURFACE ALTERATIONS INDUCED BY HARD TURNING OF AISI 52100 BEARING STEEL

Abstract

Over the last decades, turning of hardened steel for finishing purposes has earned visibility as a process that can potentially match grinding. This is due to the fact that economic advantages can be obtained when turning instead of grinding, however, turning of hardened steels has not been able to replace grinding to a greater extent owing to the difficulty of the former in providing the same level of dimensional accuracy achieved by the latter. The aim of this work is to assess the influence of cutting parameters (cutting speed, feed and depth of cut) on the dimensional and geometric deviations induced by finish turning of hardened AISI 52100 steel (60 HRC) with mixed alumina (Al2O3 + TiC) cutting tools. Additionally, the influence of the cutting parameters on the microstructure and subsurface microhardness profile is investigated. The novelty of the present work is to establish a relationship between surface (dimensional and geometric deviations) and subsurface (microstructure and microhardness variation) alterations induced by hard turning, which are crucial to the performance of the machined component. The results show that feed significantly affects diameter deviation, circularity, concentricity and surface roughness, while depth of cut affects diameter deviation and parallelism error. The influence of cutting speed is significant only with regard to the concentricity error. As far as subsurface alterations are concerned, higher surface microhardness values were obtained when combining higher cutting speed and lower feed and depth of cut. Clear evidence of microstructure alterations was observed under the most severe cutting condition only.

Keywords

• Dimensional and geometric deviations
• Hardened steel
• Microhardness
• Microstructure
• Turning