EFFECTS OF TEMPERATURE AND AL-CONCENTRATION ON FORMATION MECHANISM OF AN ALUMINIDE COATING APPLIED ON SUPER ALLOY IN738LC THROUGH A SINGLE-STEP HIGH ACTIVITYGAS DIFFUSION PROCESS

activity gas diffusion process has been investigated in this research. Effects of coating temperature and aluminum concentration in powder mixture on formation mechanism were studied using optical and scanning electron microscopes, EDS and X-ray diffraction (XRD) techniques. For this purpose two different packs containing 1 and 2 wt% aluminum powder, were used for coating the samples at two temperatures, 850ºC and 1050ºC. The ratio of Al to activator was kept constant in both packs. By increasing the Al content in high activity powder mixture, the concentration of diffused Al increased in the coating layers, and the thickness of coating increased. At 1050ºC as the rate of diffused Al to the interdiffusion zone increased, this zone gradually transformed to outer coating phases. At 850ºC coating formed by inward diffusion of Al, but at 1050ºC it was initially formed by inward diffusion of Al followed by outward diffusion of Ni. Formation mechanism of an aluminide coating on a nickel base superalloy IN738LC via a single step high.