The effect of novel composite pretreatment on performances of plasma nitrided layer

Abstract

Novel composite pretreatment combining laser shock peening and pre-oxidation was primarily adopted prior to plasma nitriding for 42CrMo steel. Optical microscope, scanning electron microscope, vickers microhardness tester and wear tester were used to systematically investigate the innovative enhancement effect of novel composite pretreatment on the performances of plasma nitrided layer. The results showed that the surface characteristics of composite pretreated sample had the advantages of both laser shock peening and pre-oxidation, thus brought out much thicker nitrided layer with excellent performances. Compared with conventional plasma nitriding, the thickness of compound layer and effective hardening layer was increased 1.8 times under the same nitriding condition. Meanwhile, the surface hardness was much higher; reaching 750 HV0.05, and the wear resistance was significantly enhanced, with nearly 60% decrease of the width of abrasive mark, comparing with that by conventional plasma nitriding without pretreatment.