Surface layer hardening of metastable austenitic steel – Comparison of shot peening and cryogenic turning

Abstract

In this paper, the effect of shot peening and cryogenic turning on the surface morphology of the metastable austenitic stainless steel AISI 347 was investigated. In the shot peening process, the coverage and the Almen intensity, which is related to the kinetic energy of the beads, were varied. During cryogenic turning, the feed rate and the cutting edge radius were varied. The manufactured workpieces were characterized by X-ray diffraction regarding the phase fractions, the residual stresses and the full width at half maximum. The microhardness in the hardened surface layer was measured to compare the hardening effect of the processes. Furthermore, the surface topography was also characterized. The novelty of the research is the direct comparison of the two methods with identical workpieces (same batch) and identical analytics. It was found that shot peening generally leads to a more pronounced surface layer hardening, while cryogenic turning allows the hardening to be realized in a shorter process chain and also leads to a better surface topography. For both hardening processes it was demonstrated how the surface morphology can be modified by adjusting the process parameter.