Nitridation of aluminum particles and formation process of aluminum nitride coatings by reactive RF plasma spraying

Nitridation of aluminum particles and formation process of aluminum nitride coatings by reactive RF plasma spraying was investigated by collecting splat and depositions and fabrication of the coating. Nitriding reaction of aluminum particles during flight in the plasma and after deposit on the substrate was confirmed by the observation of splats and the deposition morphologies, respectively. However, as nitriding reaction of aluminum particles easily forms brittle agglomerates on the substrate, the formation of sound coating was difficult. Though the coating was fabricated with the spraying condition of RF power of 5 kW, it was impossible to fabricate the coatings with RF power of 6 kW. In order to fabricate aluminum nitride coatings by reactive RF plasma spraying, it is necessary to control the plasma and the substrate temperature for the suitable conditions with changing RF power and nitrogen gas flow rate.