The exceptional properties of Ti-6Al-4V of high strength, lightweight, corrosion resistance and machinability make it one of the most widely used alloys in in the aerospace industry. Significant efforts are underway to establish powder bed additive manufacturing (AM) technologies for Ti-6Al-4V. There are also increasing attempts to use thermal and cold spray to build near net shape parts with buildup rates orders of magnitude higher than powder bed. Thermal spraying, such as HVOF, can oxidize and degrade the alloy due to the high processing temperature. Lowering the flame temperature through inert gas addition in full-size HVOF systems is a possible approach to retain solid state deposition of the feedstock particles, thereby limiting oxidation and detrimental α-case formation, while providing sufficient heat input for particle softening and plastic deformation at impact. Novel miniaturized HVOF systems, with spray jets of only a few millimetre in width, may further offer the possibility to improve the spatial resolution of the buildup for near net shape forming. The process parameter range for solid state deposition of Ti-6A-4V, using the liquid fuelled TAFA Model 825 JPid and the novel hydrogen fuelled Spraywerx ID-NOVA MK-6 with the addition of nitrogen will be discussed. Build-ups at over 80% deposition efficiency generally yield as-sprayed porosities below 3% and hardness above 200 HV100gf. Attainable microstructures and oxygen content as a function of spray parameters are delineated. Recrystallization and beta annealing of selected samples lowered the residual porosity and created equiaxed α and intergranular ß-phases. Ultimate tensile strengths of up to 1100 MPa were attained, however, at limited elongation.

Pb-Sn alloys tend to form string-like abrasion products during compressor operations, and the products cause malfunctions at the down streams of the seals and may affect the operation efficiency of the compressors. In this article, a thermal spraying method is developed for forming an abradable labyrinth seal of powdered abradable alloys to cope with the problems for improving the product quality and the operation life of the compressors. The article evaluates the abradable properties of the thermal sprayed coating labyrinth seals of the RIK-type compressors that have higher rotational speed than the other type. Various abradable properties of the sprayed coating are tested by the following test methods: microstructure observation, bond strength, machinability, bending ductility, and corrosion resistance. The article reports the results obtained from these test methods and compares them with those of the cast alloy.