Reactive atmospheric plasma spray of Al powder

Summary form only given. Reactive plasma spraying (RPS) is based on using reactive plasma to react with feedstock powders. RPS is a promising technology of material processing and coating manufacturing, especial for ceramic coatings like A1N which is expected to contribute to semiconductor equipments and so on, due to its outstanding properties [1]. However, fabrication of A1N coatings by conventional thermal spray processes was impossible due to thermal decomposition of A1N powder during spraying. In our previous study we fabricated A1N coatings through nitriding of Al powder in evacuated Radio Frequency (RF) plasma spray equipments using Ar/N2 mixture as a plasma gas [2,3]. In this study we fabricated A1N coatings through nitriding of Al powder in the air by Atmospheric plasma spray (APS) process, using N2/H2 as plasma gases. Al particles are injected in the plasma jet created by the passage of N2/H2 gases through an electric arc under high current conditions. Al particles continuously heated up (At high temperatures: above its melting point) and interacts with the plasma jet during flight to reach a certain energy state which is composed of thermal energy and kinetic energy. Al particles are fused and simultaneously accelerated by the plasma flow and gain their velocity and temperature by thermal and kinematic transfers towards SS400 substrate to be coated. Firstly we used carrier gas Ar and we found that the spray distance is an important parameter for nitriding reaction of Al powder. At small spray distance the coatings contain both Al and A1N but by increasing the spray distance the amount of A1N increases gradually, due to increase the reaction time so the possibility of Al nitriding increases, that at 300 mm spray distance the coatings is pure A1N. However, the coatings thickness decreased gradually from 100 to 20 I??m with increasing the spray distance from 150 to 300 mm, thus particles temperature decrease by increasing the spray distance so its deposition efficiency decreased. To fabricate thick A1N coatings we used N2 as carrier gas and the coating mainly A1N with thickness 100 I??m at spray distance 100 mm.