Thermal spraying of silicon nitride coatings using highly accelerated precursor powder particles

Highly accelerated powder particles obtained by low-frequency pulsed detonation spraying (LFPDS), high-frequency pulsed detonation spraying (HFPDS), and high-current pulsed plasma spraying (HCPPS) were applied with the aim to deposit dense protective silicon nitride coatings that adhere well to steel and nickel superalloy surfaces. The silicon nitride-based feedstock powders comprise α-silicon nitride with sintering additives such as alumina, yttria and minor amounts of aluminum nitride and/or silica and magnesia. Coatings were characterized by testing their critical wear path length, tensile adhesion strength, microindentation hardness, salt-spray corrosion and thermoshock resistances, and friction coefficient (pin-on-disk).