Ti and Ti-6Al-4V coatings by cold spraying and microstructure modification by heat treatment

The mictrostructure of cold sprayed Ti and Ti-6Al-4V coatings and the effect of heat treatment on coating microstructure modification was investigated. The results show that the cold sprayed Ti and Ti-6Al-4V coatings have porous structure with a high deposition efficiency. The porosities of cold sprayed Ti and Ti-6Al-4V coatings are found to be 5.4∓2.4% and 22.3∓4.7% under spray conditions. The results show that the reactions of spray particles with oxygen and the poor thermal conductivity of these materials result in a high particle interface temperature, resulting in localized melting and metallurgical bonding. Annealing at 859°C for 4 hours results in an increase in porosities of Ti and Ti-6Al-4V to coatings to 21.6∓4.6% and 29.7∓5.1% respectively, due to coalescence of incomplete interfaces and submicron pores.