Preparation And Properties Of Mechanical Energy Aided Aluminizing And Sherardizing Layers

Mechanical energy aided diffusing is a new technology about surface handling, first studied in our country in 1990's. The principle of this technology is by using the kinetic particles to impact the heated surface of the sample, because of the bombardments of the particles, the lattice atoms on the surface are activated, vacancies and other lattice defects are formed, which result in a lattice defects diffusion process in stead of a pure thermal diffusion process. As a result, the temperature and the duration of the thermal chemical process are obviously reduced.In this experiment, mechanical energy aided diffusing technology was compared with general pack powder diffusing to explore the characteristic of mechanical energy aided diffusing. Through the experiment data, more thick film in lower temperature and less time could be obtained by using mechanical energy aided diffusing method. The temperature of aluminizing reduces from 750℃to 650℃, and the time decreases from 5 hours to 4 hours. The temperature of sherardizing drops down from 550℃to 400℃, and the time also decreases more than one hour.The phase composition and the microhardness of the diffusion layer were analyzed by X-ray diffraction and microhardness apparatus. The aluminizing layer is mainly composed by Fe₂Al₅, its hardness is relatively high around 750～1000HV. The hardness of sherardizing layer is around 260～350HV.The aluminizing layer has excellent oxidation and corrosion resistance when the content of aluminum is more than 8wt%. In the experiment, the content of aluminum is more than 40wt%, so it has excellent oxidation resistance and corrosion resistance. The high temperature oxidation and the surface EIS experiment confirm the result.Although the corrosion resistance of sherardizing layer is less than Q235, it is the anode of the sample so the sherardizing layer improves the corrosion resistance of the sample. The oxidation velocity of sherardizing sample is 0.06mg/cm²Â·h and the oxidation velocity of Q235 is 0.18 mg/cm²Â·h, so the sherardizing layer a certain extent improves the high temperature oxidation resistance.