Self-propagating high-temperature synthesis of ZrB2 or TiB2 reinforced Ni–Al composite powder

The self-propagating high-temperature synthesis (SHS) of 0-40 wt.% ZrB(2) or 40 wt.% TiB(2) reinforced Ni-Al matrix composite powders has been investigated. The SHS reactions were conducted starting from elemental powders of Zr, Ti, Ni, Al, and amorphous B. For all initial compositions, the product contained only the NiAl and ZrB(2) or TiB(2) compounds without any trace of cross-reaction phases. The powder, obtained by grinding the reacted pellet, contained ZrB(2) or TiB(2) homogeneously dispersed in the NiAl matrix. The dimension and distribution of the reinforcement phase make the powder suitable as precursor for thermal spray applications. After sintering of the composite powder up to 85% of theoretical density, microhardness was measured. The microhardness of pure NiAl was 394 +/- 37 HV(0.2). It increased considerably by the addition of the boride phases. Samples containing 40 wt.% ZrB(2) and TiB(2) attained values of 812 +/- 94 and 967 +/- 104 HV(0.2), respectively.