Preparation a nickel-aluminide bonded diamond tool by self-propagating high-temperature synthesis and strengthening by nickel-chromium-phosphorus alloy and copper

Abstract

Metal bonded diamond tools are normally manufactured by hot-press sintering, which is a high energy consuming process and using a large number of graphite moulds as well. Graphite dust is hazardous to operator's health and environment in machining of graphite mould. In present study, a metal bonded diamond tool is manufactured by self-propagating high-temperature synthesis (SHS) without hot press sintering and consuming of graphite moulds. In order to improve bonding of diamond grit and flexural strength of the tool for this method, nickel‑chromium‑phosphorus alloy and copper are introduced into nickel‑aluminum SHS in present study. The influence of nickel‑chromium‑phosphorus alloy and copper content on the combustion processes, the thermal behaviors, and the microstructures of the synthesized composite bonds are examined in detail. A diamond tool based on the optimized composite is prepared, and the grinding performance is examined. The results reveal that the addition of nickel‑chromium‑phosphorus alloy and copper inhibited the SHS reaction of nickel‑aluminum and reduced the combustion velocity, combustion temperature and reaction exothermic enthalpy. Copper can significantly improve flexural strength of the nickel aluminide bond. However, the maximum of nickel‑chromium‑phosphorus alloy or copper is about 60 wt% to sustain the SHS. A homogeneously dispersed and interconnected nickel-chromium-phosphorus phase in the matrix of nickel aluminides can be obtained with addition of over 40 wt% nickel‑chromium‑phosphorus alloy. A continuous chromium rich layer, composed of chromium carbide, has been formed at the interface between diamond grit and matrix, which renders a chemical bond of diamond grit. On the basis of the addition of 40 wt% nickel‑chromium‑phosphorus alloy and 10 wt% copper, an interconnected nickel‑chromium‑phosphorus phase for strong bonding of diamond grit and a flexural strength up to 700 MPa are achieved, which is considered as an excellent candidate material for diamond tools. The grinding test shows that the diamond tool owns a sound machining ability on the granite, and the diamond grit can be well retained and protruded.