Temperature dependent properties of Co-W-C alloys

Abstract

Integrated Computational Materials Engineering (ICME) supports materials engineering by linking materials models at multiple length scales. Effective use of the ICME approach requires underlying data to fully enable a combination of appropriate models and software tools. In the Hardmetal world where materials are composites of hard carbides/nitrides with tough metal binders this requirement has many facets. This paper addresses one of these facets - the issue of the mechanical behaviour of typical Co based binder phases over a range of temperatures. Three Co-W-C alloys were manufactured to provide samples that could be tested at different temperatures and under various mechanical conditions. The principle of miniaturised testing was adopted to help generate as much information as possible from a restricted amount of original alloy. An important aspect was the phase content of the alloys since Co alloys can be FCC, HCP or HCP/FCC mixtures and resistivity measurements as a function of temperature were used to interpret the phase contents. Below the FCC/HCP phase transformation temperature the microstructure can be a mixture of HCP/FCC, dependent on composition and whether applied heating is increasing or decreasing (hysteresis in phase transformation kinetics). To fully characterise all these parameters and their effect on mechanical properties at different rates would be a significant effort in material manufacture, sample characterisation and testing resources. Consequently, an attempt was made to conserve resources by exploring these issues by completing multiple tests on a few samples of each of the three alloys, while in both the heating and cooling regimes.