Performance Enhancement of Powertrain Shaft Through Carbo-Nitriding Surface Treatment

Abstract

This research is done with the purpose of revealing an increase in the fatigue performance of carbo-nitrided powertrain shafts followed by the second tempering. The fatigue test was conducted at a bi-directional torsional cyclic load using an MTS torque tester. Various investigations were carried out to find out the effect of surface roughness, second tempering, inter granular oxidation, retained austenite, and residual stress. The result of this investigation shows that an increase in the carbo-nitriding processing time causes higher inter granular oxidation and a non-martensitic transformation product. The existence of the surface retained austenite has not influenced notably the enhancement in the fatigue life performance in the powertrain shaft. Existence of martensite with the removal of the non-martensitic transformation product from the shaft surface enhanced the fatigue performance significantly—up to 300% (from 12 000 to 40 000 cycles).