Microstructural Effects and Properties of Non-Line of Sight Coating Processing via Plasma Spray-Physical Vapor Deposition

Plasma Spray-Physical Vapor Deposition (PS-PVD) is a unique processing method that bridges the gap between conventional thermal spray and vapor phase methods, enabling tailorable coatings in thin dense layers or columnar microstructures. The strengths of this processing technique are material and microstructural flexibility, deposition speed, and potential for non-line-of-sight (NLOS) capability by vaporizing feedstock material into the plasma stream. High plasma temperature and low pressure combined with viscous gas flows enable deposition of coatings around complex shapes and NLOS coverage. Oxide coatings were deposited on cylindrical substrates using PS-PVD. The effects of impingement angle and flow attachment had significant effects on the deposition mode, ranging from cluster deposition to entirely vapor transport. These modes produced different microstructures and properties, which were deposited on flat substrates for evaluation of erosion performance, thermal conductivity, and thermal cycling life. Coating microstructure and phase analysis were performed using X-ray diffraction and electron microscopy.