The structure and the properties of WC-Co samples produced by SLM technology and carbon-doped prior to HIP processing

Abstract

The purpose of this study is to verify how the carbon doping of the WC-Co cemented carbide (CC) affected their structure before their processing by hot isostatic pressing (HIP) technology. The samples for this experiment were fabricated by selective laser melting technology (SLM) using a YAG fiberl aser with a power of P = 40 W and a scanning speed of 83 mm/s. The subsequent carbon doping process was performed in a chamber furnace at 900 °C for 1, 4 and 12 h. The HIP was performed at 1,390°C and pressures of 40 MPa, 80 MPa and 120 MPa. The changes induced in the structures were evaluated using X-ray diffraction and various microscopic methods. X-ray diffraction analysis showed that the structure of the samples after SLM consisted of WC, W2C, Co4W2C and Co phases. As a result of the increase in the carbon content in the structure of the samples, the transition carbide W2C and structural phase Co4W2C decayed. Their decay was manifested by the coarsening of the minor alpha phase (WC), which occurred both during the carburizing process and during the subsequent processing using HIP. In the samples in which the structure was carburized prior to HIP, only the structural phases WC and Co were observed in most cases.The results confirm that it is possible to increase the homogeneity of the CC structure and thus its applicability in practice by additional carburization of the sample structure with subsequent processing by HIP technology.