Effect of Mo addition on microstructure, mechanical and machinability properties of Cr-PM steels

Abstract

In this work, it was investigated the effect of molybdenum (Mo) addition on machinability, mechanical properties, and microstructure of Cr steels produced by using powder metallurgy method. Tensile and hardness experiments were applied to define the mechanical properties of the produced Cr-PM steels. The machining experiments have been also performed without coolant on a CNC vertical machining center at three different cutting speeds (150, 210, and 270 m/min), two different feed rates (0.4 and 0.8 mm/tooth), and constant depth of cut (0.5 mm). The machinability of the alloys was evaluated in regard to surface roughness (Ra) and tool wear (Vb). The results indicated that that Cr-PM steel with 5% Mo addition by weight had the highest yield, tensile strength, and hardness, and the best surface quality was obtained in this sample in terms of surface roughness. However, according to Vb measurement results, the cutting performance of the cutting inserts wasnegative affected by MoC(N), CrC(N), and MoCrC(N) precipitates formed in the microstructure of PM steel.