Evaluation of the mechanical properties and machinability of chromium and molybdenum-added powder metallurgy steels

Abstract

The present study focuses on the microstructure, mechanical properties, and machining aspects of powder metallurgy (PM) steel containing different rates of chromium (Cr) and molybdenum (Mo). PM steel alloys were pressed at 700 MPa and sintered at 1400°C in a mixture of nitrogen and hydrogen atmosphere for 1 hour. While the precipitates and fracture surfaces of the samples obtained were examined by scanning electron microscope (SEM) and EDS analyzes, the grain size and phase distributions were also examined with an optical microscope. Moreover, tensile and hardness measurement tests were carried out to determine the mechanical properties of the samples with different ratios of Cr and Mo content. The milling experiments were also performed without using coolant in a CNC milling machine at different cutting parameters. The surface roughness (Ra), tool wear (Vb), and wear mechanism were investigated under these conditions. The outcomes of this study reveal that the yield and tensile strength values of the samples with the addition of Cr and Mo increased but the elongation value decreased. The results also stated that the most effective process parameter for both Vb and Ra was the workpiece material and the regression models developed to estimate the output parameters (Vb and Ra) give successful results with high determination coefficients (R²) of 98.05% and 98.11%, respectively.