Abstract: MCrAlY bond coat is deposited onto GH99 high-temperature alloy by using high velocity oxygen fuel technique. The influence of this technique on the oxidation resistance is studied. The experimental results show that lots of sharp-angled and hooked grains exist on the surface of the APS-bond coat, while the surface of HVOF-MCrAlY is relatively smooth and with less internal black oxide. A layer of compact granular oxide forms on the surface of HVOF-MCrAlY after 15 min oxidation, the weight gain of HVOF sample is faster than that of the APS sample in the first 40min oxidation, then becomes slowly, while the APS sample still has high oxidation rate. HVOF sprayed coating of thermally grown oxide(TGO) appears delamination after 300 hours oxidation, TGO layer close to bond coat has dense organization, TGO layer close to top coat has lots of holes and gaps in it. Due to high velocity oxygen fuel technique, time for TGO coming into steady-state oxidation stage is shortened and the period of steady-state oxidation becomes longer. The high temperature oxidation resistance of coating could be improved obviously.

Key words: High velocity oxygen fuel, High-temperature oxidation, Thermal barrier coating, Thermally grown oxide