Preparation of Ti–Cr and Ti–Cu flame-retardant coatings on Ti–6Al–4V using a high-energy mechanical alloying method: A preliminary research

Abstract

The Ti–Cr and Ti–Cu coatings with the in situ forming intermetallic phases were fabricated on the substrates of Ti–6Al–4V alloy using a novel high-energy mechanical alloying method. The coatings exhibited the flame-retardant function on the common Ti alloy which was characterized by the phenomena of spontaneous combustion under some certain environmental conditions. The solid-state processing to prepare the flame-retardant coatings was finished in a planetary ball-mill with a further designed vial. Some stable intermetallic phases were formed on the basis of the initial instable non-equilibrium phases during the mechanical alloying processes. Using the optimized process parameters, the suitable diffusion layer appeared at the interface of the coating and the inner surface of substrate. The effects of the milling durations on the formation quality of coatings were emphasized. Following the analyses of the experimental results, the formation mechanisms of the deposited coatings prepared by the mechanical alloying method were detailed in terms of four assumed steps. The coating adhesion strengths were evaluated by scratch tests and then measured according to ASTM G171-03 Standard. The flame-retardant functions of Ti–6Al–4V substrates with Ti–Cr and Ti–Cu coatings were evaluated through the laser spot melting testing on the surfaces.