Alloying of Cold-Sprayed Al-Ti, Al-Ni Composite Films

Abstract

Abstract The Al-Ti, Al-Ni mixed powders were successfully coated by cold gas dynamic spray process (CDSP) and alloying behaviors of films after post-annealing were investigated. The particles were accelerated through a standard de Laval type of nozzle with 120psi (prior to enter). Instead of conventional He gas, the air was used as particle carrying gas. The as-purchased power size of Al, Ti, Ni, was 77, 44, and 3, respectively. The composition of Ti and Ni was varied from 10 and 30 wt%. The coated films were annealed at 600~630. in air or N2 atmosphere for 3 hrs. It was observed that Ni and Ti particles were finely dispersed and imbedded densely in Al matrix. After post annealing of Al-Ti and Al-Ni films, alloy phases such as the Al3Ti and Al3Ni phase were formed in the films. In case of Al-Ni films after annealing in air, the oxidation process seemed to retard the alloying of Al3Ni. However, after annealing in N2, the limitless alloying was proceeded until Ni particles were all consumed. In case of Al-Ti films, it was found that oxidation were virtually nonexistent even in air atmosphere. The formation of Al3Ti seemed to be limited by Al or Ti diffusion via preformed Al3Ti phase encapsulating Ti powder. In bond strength test, Al-Ti and Al- Ni composite films have higher adhesive bond strength up to 2~ 3 times more than pure Al coating due to massive crater formation of hard Ni or Ti particles. In conclusion, CDSP of Al-metal composite powder source can be a practical and economical way to prepare hard and adhesive Al-alloy thick films owing to stable and finely dispersed inter metallic compound formed in low Temperature annealing. Abstract only; no full-text paper available.