Oxidation Resistance of Al PO 4 Bonded Ceramic Coating Formed on Titanium Alloy for High‐Temperature Applications

Al PO 4 based coatings were prepared on T i‐6 A l‐2 Z r‐1 M o‐1 V titanium alloy using aluminum phosphate as a binder and A l 2 O 3 / C r 2 O 3 based mixing particles as the fillers. The microstructure, phase and chemical composition of the coatings were analyzed by SEM , XRD and EDS techniques. The high temperature infrared emissivity values of coated and uncoated titanium samples were tested. The results show that the coating had a higher infrared emissivity value (>0.8) than titanium substrate (0.15–0.3) in the wide wavelength range of 5–20 mm, which is attributed to the uniform dispersion of high emissivity A l 2 O 3 and C r 2 O 3 particles in the Al PO 4 binder matrix. The coated titanium samples exhibited excellent oxidation resistance performance with significantly decreased oxidation rates at 600 and 800°C. The mass gain of the coated sample kept at a low and stable constant of 0.15 mg/cm 2 , significantly lower than that of titanium substrate (0.54 mg/cm 2 ) when oxidized at 600°C up to 100 h.