REACTIVE POWDER-METALLURGY OF NI3SI-BASED ALLOYS

Nickel silicides offer interesting properties for applications in high ly corrosive environments at intermediate temperatures. These material s can be produced by reactive powder metallurgy, thus bypassing the ne ed for expensive prealloyed powder and avoiding the difficulties accom panying casting. In reactive processing, controlling the reaction is e ssential to obtain an acceptable product quality. Controlling the synt hesis of intermetallics can be achieved by several methods, such as di lution of the elemental powders with prealloyed powder, in situ format ion of the intermetallic at a low;temperature, or mechanical alloying. Hot isostatic pressing (HIP) greatly improves the properties of the p roducts compared to the reactively sintered materials. The HIP treatme nt can be applied as a post treatment, or as KIP combined with reactiv e sintering.