Effect of Isothermal Aging on Microstructure Evolution of Ni Claddings on Inconel 617

In this work, gas tungsten arc weld was employed to produce corrosion-resistant Ni claddings on the surface of Inconel 617. The effect of isothermal aging on the microstructure of Ni claddings was studied at 850 °C for up to 3000 h. Results show that isothermal aging can promote the release of welding residual stress. Recrystallization begins to appear in the Ni claddings when the aging time reaches 2000 h. Hardness values and chemical compositions of Ni claddings are changed slightly during the whole aging process. TiN phase is precipitated in the Ni claddings before and after isothermal aging, while their quantity and morphology do not change significantly. Low chromium concentration and extremely low chromium diffusion coefficient in Ni claddings indicate that the Ni claddings have excellent corrosion resistance to molten salts.