The Study On The Preparation Of Porous Nickel-Based Alloy Through Plasma Spraying

According to the self-fluxing alloy Ni15, porous nickel-based alloys were prepared by atmospheric plasma spraying technology and three kinds of heat treatment(including the electric furnace heating remelting, oxygen-acetylene flame remelting and induction remelting technology). Using laser scanning confocal microscopy to observe the microstructure of the prefabricated samples and analysis the reason which make the differences. Microhardness is gotten by hardness tester and coefficients of thermal expansion by dilatometer. The prefabricated samples were tested by using tensile-compression testing machine and real-time data acquisition instrument for small strain compression tests.In the experiments, four kinds of mixed powder with different components are prepared to manufacture eight kinds of Ni15 based porous samples by atmospheric plasma spraying technology and three kinds of heat treatment. The samples which containing 25%Nickel-Graphite have a good microstructure after oxygen-acetylene flame remelting. Its graphite phase and pores are evenly distributed and hardness value is 179.8HV and the porosity rate is 27%. The other seven samples, respectively, have problems of poor remelting result, uneven hardness, uneven pore structure, too low porosity rate or too high porosity.The thermal expansion and compression performance of the preferred porous samples was tested and it was compared with solid metal nickel-based alloys. The results showed that:the thermal expansion coefficient of the porous samples was enhanced with the increase of temperature and the thermal expansion coefficient of the porous solid sample is lower than the solid metal at the same temperature. With the decrease of the porosity, the thermal expansion coefficient increases. The elastic modulus of the porous sample was significantly lower than the solid metal and with the decrease of the porosity, the elastic modulus of the porous sample increases. The elastic range of the porous sample is slightly higher than the solid metal and it will be reduced with the decrease of porosity. The high temperature has a significant effect on the elastic modulus and the elastic range of the porous samples and with the increase temperature, elastic modulus was increased and the elastic range was decreased.