Influence of commercial MCrAlY powders on thermal cycling behaviors of TBCs with nano-structured YSZ

This study investigates the thermal cycling behavior of HVOF-MCrAlY combined with APS-nanostructured YSZ（nYSZ） thermal barrier coatings（TBCs） produced using three commercial MCrAlY powders commonly utilized by gas turbine original equipment manufacturers（OEMs） and maintenance，repair，and overhaul（MRO） companies，within a temperature range from ambient to 1150 ℃. Among the coatings，HVOF-A386-2.5+APS-nYSZ exhibits the longest furnace cycle testing（FCT） life，while HVOF-A9624+APS-nYSZ has the shortest. However，the differences in FCT life among the three TBCs are insignificant. All three coatings fails in a manner similar to conventional HVOF-MCrAlY+APS-YSZ（mYSZ） coatings，primarily due to crack propagation and coalescence in the APS-YSZ layer near the YSZ/MCrAlY interface，resulting from interface separation at mYSZ/nYSZ and mYSZ/mYSZ interfaces. The thermally grown oxide（TGO） layer grows fastest on the HVOF-A9624 surface，whereas the growth rate is slowest on the HVOF-A386-2.5 surface. However，the variations in TGO growth rates among the three coatings are relatively small. It is anticipated that increasing the surface roughness of the HVOF-MCrAlY may strengthen the YSZ/MCrAlY interface，thus mitigating crack propagation and coalescence in the TBC. Additionally，reinforcing the YSZ/YSZ interface can enhance resistance to interface separation and surface cracking. Furthermore，controlling the aluminum（Al） content in the MCrAlY and/or doping alloy elements into the MCrAlY may slow down diffusion，reducing the TGO growth rate and preventing excessive formation of mixed oxides. These strategies may collectively contribute to improving the durability of HVOF-MCrAlY+APS-YSZ TBCs under thermal cycling conditions.