Making NiTi intermetallic compound coating using laser plasma complex spraying.

To improve the erosion resistance of the Ti-alloys, surface modification technique using complex spraying system coupled with a high powers CO2 laser and a DC plasma gun was applied. The laser plasma complex spraying system (LPCS) was constructed with 5kW CO2 laser and low pressure DC plasma spraying unit. In this system, the plasma spray coated layer was remelted and rapidly solidified by the CO2 laser irradiation, So, it is possible to synthesize intermetallic compound coatings from the simply mixed. powder. NiTi intermetallic compound is known as a high cavitation erosion resistant material. In a case of only plasma spraying process, Ti and Ni layer were separated mutually in the coatings, but by the laser plasma complex spraying, NiTi, NiTi2, and Ni3Ti intermetallic compounds were formed in the coatings. And the coatings were joined metallurgically with substrate and contained few defect. The ratio of phases such as NiTi, NiTi2, and Ni3Ti was varied with the laser irradiation conditions and powder mixed ratio. To evaluate the erosion resistance of the coatings, vibratory cavitation erosion tests were carried out, The cavitation erasion resistance of the coatings were about 20 times as much as Ti6Al4V substrate due to NiTi phase.