Grindability of TiC-Ni₃Al metal matrix composites

TiC-Ni₃Al metal matrix composites with 40-60 vol% hard phase concentration have been developed as candidate materials for diesel fuel injector plungers. They possess good mechanical properties and similar thermal expansion rate to the steels used for the injector bores. Previous studies have confirmed their high scuffing resistance in fuel-lubricated environment. However, machining of these composites has been quite challenging, especially when high material removal rate (MRR) or precision surface finish are required, due to their relatively high toughness and non-uniform distribution of hard phases in the microstructure. This paper presents a grindability study on TiC(50 vol%)-Ni₃Al using different diamond grinding wheels at a variety of grinding conditions. Alumina and silicon nitride were used as baseline materials for comparison. The maximum material removal rate (constrained by machine power) of this composite material was slightly higher for conventional grinding than for creep feed grinding, while much lower compared to alumina in either case. While comparable average surface finish was generated by creep feed and conventional grinding, more severe surface damage was observed for creep feed grinding. The lower abrasive concentration wheel generated lower tangential force and consumed less power, but produced a rougher surface. Lower wheel speed may increase grinding efficiency but would sacrifice the surface finish. A worn-out wheel generally consumes much more grinding power while produces smoother surfaces.