Effect of Particle Morphology on Physical, Mechanical and Wear Properties of Cobalt Metal Powders

Abstract

Cobalt is used in applications that require high densities and good mechanical properties. Cobalt powder is used in batteries, cemented carbides, stainless steel, machine tools and also in manufacturing of metal matrix diamond tools designed for the cutting and drilling of hard rocks and concrete. This study aimed to investigate the structural properties and compare the mechanical and micro structural properties of two different cobalt powders, specifically the spherical grain (Co-S) and rod-like grain shapes (Co-R), to enhance the cutting performances of the diamond cutting tools. The flow properties of the powders, as a function of the shear strain rate, were determined using Freeman Technology (FT4) rheometer analysis. The microstructural characterizations were conducted using scanning electron microscopy (SEM)-energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analyses, and the crystallite size values were calculated using the Williamson-Hall method. The mechanical characterizations were conducted using the density measurement, hardness, compression test, and wear test. Based on the results of the FT4 rheometer analysis, the Co-S powder had higher compressibility and air permeability compared to the Co-R powder. The SEM analysis of the sintered samples revealed multiple pores in the Co-R powder. The highest mechanical properties were obtained in the sintered sample of the S series. The most suitable Co powder for the preparation of metal matrix mixtures of diamond cutting tools produced using SPS was determined to be the Co-S series.