The optimization of machining parameters by Taguchi method during turning of 15-5 pH stainless steel

In the recent years, 15-5 PH precipitation hardenable martensitic stainless steel has been widely used especially in the aviation and nuclear industry due to its high strength, good corrosion resistance and lower distortion properties. However, it is ranked in the hardly machinable materials classification because of this excellent mechanical properties. The aim of this study is to investigate the effects of machining parameters on the cutting force (Fc) and surface roughness (Ra) during turning of the 15-5 PH stainless steel and to specify the optimum machining conditions. For this purpose a test design will be carried on with Taguchi L18 orthogonal array by defining the cutting speed, feed rate and cutting depth at three different levels and the cutting tool at two different levels. To indicate the effect of precipitation hardening heat treatment on machinability, 15-5 PH and precipitation hardened 15-5 PH (H1025) materials will be used. Machining tests will be carried on at the CNC turning machine under dry cutting conditions by using coated cementite carbide cutting tools. At the end of the tests, variance analysis (ANOVA) will be made for the Fc and Ra values which are obtained depending on the cutting parameters and the effect of machining parameters on the Fc and Ra will be examined. Besides, a regression analysis will be made to put forth the relation between the dependent and independent variables. It has been seen that depth of cutting is the most efficient parameter on cutting force and feed rate is the most efficient parameter on surface roughness while processing both two materials. It has been determined that precipitation hardening heat treatment increases cutting force and surface roughness. It has been obtained that CVD TiCN-Al2O3-TiN covered tool has gained an advantage over PVD TiAlN-AlCrO covered tool on processing outputs.