Microstructures and Properties of Porous Ni-based Coatings

A porous Ni-based coating was fabricated by plasma spraying and subsequent remelting. The microstructure, thermal expansion coefficient and mechanical properties during compression process were analyzed by scanning electron microscope (SEM), micro-hardness tester, thermophysical properties instruments and so on. The results show that the closed and spherical pores with 30 similar to 100 mu m in diameter are formed in the remelted coating. The elastic modulus of the porous coating descends by 69.5% and elastic deforming scope ascends by 68.7% with the porosity increasing to 30.6% from 0.53%. The average linear thermal expansion coefficient decreases with the increasing of porosity in the temperature scope between 40 and 220 degrees C. The improvement of elastic deforming scope of Ni-based alloy due to the formation of closed pore results in the decline of thermal expansion coefficient, to achieve the purpose of low thermal expansion and high recoverability.