Optimization of Cryogenic Treatment to Maximize the Wear Resistance of Chrome Silicon Spring Steel by Taguchi Method

Deep Cryogenic Treatment (DCT) is an add on process over the conventional heat treatment on steel components, carried out in such a way that the material is slowly cooled down to the cryogenic temperature, held at that temperature for a specified period of time, heated back to the room temperature in a slow rate followed by low temperature tempering. The main advantage of DCT is that, it enhances the wear resistance. The various levels of DCT process parameters have its influence over the wear resistance of the material. In this study, the Taguchi method is used to optimize the process parameters of DCT for a commercial piston ring, made up of Chrome silicon spring steel (SR10) to obtain maximum wear resistance. The DCT parameters considered for optimization are cooling rate, soaking temperature, soaking time, tempering temperature and tempering period. Two iterations of Taguchi design were used. During the first iteration, L162¹⁵ Orthogonal array (OA) was used to conduct the Taguchi experiment so as to study the significance of these factors and the effect of their possible two factor interactions. In the second iteration, L93⁴ OA was used to conduct the Taguchi experiment to arrive at the optimal levels. Wear test was conducted on a reciprocatory friction and wear monitor by weight loss method, as per ASTM standards G181 and G-133. The relative importance of the controlling parameters of DCT and their interactions for enhancing the wear resistance were evaluated in terms of their percentage contributions using Analysis of variance (ANOVA). Thus the optimum levels of the DCT parameters for SR10 steel ring were arrived. Confirmation test was conducted and the results fall with in the confidence interval.