Surface Integrity and Fatigue Strength of Hard Milled Surfaces

Tool flank wear during hard milling adversely affects surface integrity and, therefore, fatigue strength of machined components. Surface integrity and machining accuracy deteriorate when tool wear progresses. In this paper, surface integrity and its impact on endurance limit of AISI H13 tool steel (50 ± 1 HRC) by milling using PVD coated tools are studied. The evolutions of surface integrity including surface roughness, microhardness and microstructure were characterized at three levels of tool flank wear (VB = 0, 0.1mm, 0.2mm). At each level of tool flank wear, the effects of cutting speed, feed, and radial depth-of-cut on surface integrity were investigated respectively. Fatigue endurance limits of the machined surfaces at different reliability levels were calculated and correlated with the experimentally determined fatigue life. The good surface finish and significant strain-hardening on the machined surfaces enhance endurance limit, which enables machined components have a fatigue life over 10₆ cycles.