Low content and free cobalt matrixes for diamond tools

In the present work several titanium alloys were evaluated as matrixes for diamond tools. The purpose is to find new metal matrixes not containing cobalt or with the amount minimised. Due to the low expansion thermal coefficient of titanium, diamond composites were produced by pressureless sintering, that means a relevant economic saving. The effect of different Ti–Ni ratio and of small aluminum and cobalt additions on the mechanical properties of the alloys was investigated. The monolithic metal alloys and diamond composites were characterized by density measurements. The structure was investigated by X-ray diffraction analysis (XRD), the microstructure by optical and electron microscopy. Hardness as well as erosion tests were performed as mechanical characterization. The diamond retention capability and the metal-diamond interface were evaluated by electron microscopy on the fracture surfaces of composites. Crack free composites, presenting high relative density, were obtained. They show a strong diamond-metal interface. No graphitization evidence on diamond particles was observed. Hardness value and an erosion resistance comparable with that of hot pressed cobalt was registered in some cases.