Residual stress profiles of plasma nitrided steels

Abstract

It is well documented that plasma nitrided steels exhibit superior fatigue resistance by virtue of induced compressive residual stress. In the present paper, six steels with different alloying elements and contents were plasma nitrided for 4 and 9 h at 580°C. These were then analysed in terms of microstructural features, microhardness profiles, and residual stress distribution. A Philips X-ray diffractometer was used for phase determination and residual stress measurement. The paper discusses the use of X-ray diffractometry to measure residual stress, emphasising the significance of K calibration, choice of ψ angle, and validation of 2θ measurement. Results showed a close relationship between microhardness profiles and residual stress distribution. Effects of the various alloying elements such as Cr, Al, Ti, W, and V were explored in terms of their plasma nitrided microstructural features as well as their contribution to surface hardness and case depth.