In situ processing aluminide coatings with and without tungsten carbide

Alloying elements have been added to β-NiAl to improve strength and creep resistance at high temperature enhancing β-NiAl attractiveness and competitiveness. Particularly, tungsten carbides (WC) have been used to modify this aluminide, resulting in an increase in hardness and improved its tribological behavior in high temperature. However, the size of WC particles and the processing conditions account for the microstructure obtained and the resulting properties. This study takes an important step toward understanding how carbide particle size can contribute or interfere in the synthesis and microstructure of NiAl-based coatings. NiAl intermetallic coatings were processed by in situ synthesis during deposition by plasma transferred arc (PTA). Powder mixtures of elementary Ni and Al powders with and without the addition of 1 wt% carbide microparticles and of 1 wt% WC nanoparticles. Carbide microparticles increased the dilution with the substrate and consequently the density of point defects, which had a strong impact on hardness. However, the addition of WC nanoparticles had a negative impact on the synthesis of NiAl, delaying/inhibiting its formation, which was reflected on the microstructure and low hardness of coatings.