High Strength Stainless Steel Mechanical Energy Aided Aluminizing Process

With high strength-toughness and low sensitivity to stress concentration in the dynamic and static load high-stress stainless steels were widely used in aeronautics and astronautics,petroleum industry and transportation industry. In its service environment, high-stress stainless steels application were limited to its poor wear resistance, oxidation resistance and the corrosion resistance, and reduc its service life. Surface treatment can be used in steels to improve its performance. After aluminized, the compact alumina membrane can be formed on the steel surface, and it is an effective mean to improve its wear resistance,oxidation resistance and the corrosion resistance. Since high-strength stainless steel in paper the final aging temperature is 540℃, traditional aluminizing process such as solid power aluminizing, hot-dip aluminizing, the aluminizing temperature higher than 540℃, and would change mechanical properties of the matrix material; though the aluminizing temperature of physical vapor deposition aluminizing is low in 540℃, the binding force of aluminized layer is not stronger, expensive equipment, and other shortcomings restrict its application. In the paper, high-stress stainless steel is aluminized with machnical energy adied aluminizing process, and and reliable aluminized layer is got on keeping the mechanical properties of the matrix material the same as before.After systematic study on the aluminizing agent formula and parameters of machnical energy adied aluminizing process, the feasible aluminizing agent formula of high-stress stainless steel machnical energy adied aluminizing process is got, that is 30%wt aluminum powder+10%wt aluminum iron powder+2%wt NH4Cl+4%wtCeO2+140 mesh A12O3 (allowance). The experimental results also show, that the main influence factors of mechanical energy aided aluminizing process is the aluminizing time, the roller speed and the loading amount of penetration for 1Cr15Ni4Mo3N material. Study for parameters of machnical energy adied aluminizing process, the optimal machnical energy adied aluminizing process is got, that is aluminizing temperature 500℃, aluminizing time 10-14h, the roller speed 8-10r/min, the loading amount of penetration 70%-80%(volume ratio),vacuum pumping and pass into Ar gas to protect. Through the optimal machnical energy adied aluminizing process and the aluminizing agent formula, this technique produce aluminized layers with thickness of 11μm and appear to be homogeneous for 10h treatment at 500℃on 1Cr15Ni4Mo3N material surface, base on keeping the mechanical properties of matrix material isn't changed and aluminizing time was reduced by half, compared to solid powder aluminizing process.The element distribution of aluminized layer is analyzed by using SE and X-ray diffraction, also the phase structure of aluminized layer. Found that the mechanical energy aided aluminized layer was a single layer, and the layer composed mainly by Al-rich phase such as Fe2Al5, Fe4Al13. Also, the performance of the mechanical energy aided aluminized layer are tested by micro hardness, thermal shock and oxidation experiments, and discover that the aluminized layer have excellent resistance to middle temperature oxidation and strong combination with matrix material, also, the micro-hardness of aluminized layer is more than two times than that of matrix material. By neutral salt spray test and electrochemical tests showed that the mechanical energy aided aluminized layer has greatly improve chloride corrosion resistance compare to the base material. And compared to solid powder aluminizing process, the mechanical energy aided aluminizing process have more advantages on the chloride corrosion resistance.