Corrosion Behavior Of Two Directional Solidification Super Alloy In Different Mediums

Gas turbine engine has been widely used in the field of aviation as a power unit. With the rapid development of the aerospace industry, the demand of the performance of blade material in the gas turbine engine has become higher and higher. Due to the combined effect of Na2SO4 generated by the fuel combustion and NaCl in the seawater, the gas turbine engine that is working in the coastal environment will be subject to hot corrosion, which also accelerates the failure of the blade. Therefore, it has become a significant issue to make in-depth research into the corrosion behavior and mechanism in different media.By making use of a series of equipments such as high temperature heat treatment furnace, optical microscope, scanning electron microscope and X-ray diffract meter, this paper has made an analysis of the corrosion behavior and mechanism of two directionally solidified super alloys in the saturated Na2SO4 saturated NaCl and 75% Na2SO4+25% NaCl(wt.%) at the temperature of 700 degrees.The research result of the corrosion behavior of directionally solidified nickel-based alloy shows that the corrosion products at 700? and covered with 100%Na2SO4 include Al2O3,NiO,Cr2S3,Ni3S2,NiCr2O4 and TiS while the corrosion products at 700? and covered with 100% NaCl include Na2CrO4,NiO and Al2O3. What is more, the corrosion products at 700? and covered with 75%Na2SO4+25%NaCl include Al2O3,NiO, TiO2, CrO,CrS,Ni3S2 and CoCr2S4(in small quantity). The alloy that is put in the 75%Na2SO4 +25%NaCl(wt.%) has displayed a relatively high level of corrosion and the heating treatment will also eliminate the composition segregation to make it more even in structure and corrosion resistant.The research result of the corrosion behavior of directionally solidified cobalt-based alloy shows that DZ40M alloy has displayed different levels of corrosion resistance in different corrosion media, highest in the mixed salt solution and lowest in the Na2SO4. What is more, the state of the alloy has a great effect on the capability to resist hot corrosion. Compared with the cobalt-based alloy, the alloy that received heating treatment on the corrosion resistance. The result of electrochemical corrosion test shows that the capability of corrosion resistant will be weakened after the heating treatment. On the whole, the corrosion of DZ40M has been the mixture of hot corrosion and electrochemical corrosion, suggesting that the corrosion mechanism is quite complicated.