Study on the microstructure of NiCoCrAl sheet deposited by EB-PVD at 800°C

The microstructure and hardness of NiCrCoAl sheet deposited by Electron Beam Physical Vapor Deposition (EB-PVD) at 800°C for different holding times (2 h; 4 h; 16 h; 30 h) in vacuum of 5 × 10^-3 Pa were studied in this paper. The results shown that the original state was γ-Ni solid solution with homogenous and fine micro structure and without dislocations and precipitates but twin crystals and strain stripes in the grains. The phase structure didn't change at 800°C and in vacuum of 5 × 10^-3 Pa with sheet and layer microstructures and lots of substructures defects such as twin crystals and some dislocations on the surface and cross-section in the superalloy. But a few carbonides were separated and precipitated when held at 800°C. for 16 h in the superalloy. With the increase of held time, the strain stripes disappeared and the grains grew rapidly along the preferential orientation of (220) crystal face, then the microhardness fell down at the same time.