Study On The Mechanical Energy Aluminized Of AM355 Stainless Steel By Ceramic Balls Impact

The mechanical energy aided aluminizing process with ceramic balls impact was used to aluminizing on the surface of AM355 stainless steel in this paper. The effects of different ceramic balls parameters on microstructure,chemical composition distribution and the formation rate of aluminized layer were investigated by X-ray diffraction, scanning electron microscopy with energy dispersive spectrum, and optimize the best parameters of ceramic balls. On the other hand, the micro-hardness, mid-temperature oxidation resistance and corrosion resistance were tested to compare the different performances of the aluminized layer prepared by the mechanical energy aided aluminizing process with ceramic balls impact and pack cementation process. On the basis of this, the reaction between aluminizing agent, adsorption and diffusion of active atomic in the aluminizing process, and find out the mechanism of mechanical energy aided aluminizing process with ceramic balls impact. The results are as follows:At the same aluminizing medium condition, the thickness of aluminized layers prepared by the mechanical energy aided aluminizing process with different parameters ceramic balls impact at 550? aluminizing for 5h, which gradually reduced with the increase of mass ratio and diameter of ceramic balls. When the parameter of ceramic ball is 5wt%, and 1mm, the aluminized layer thickness reaches the most 59?m, which is about 2 times more than that prepared by traditional pack cementation, and which is significantly higher than that prepared by mechanical energy aided aluminizing without ceramic balls impact.The aluminized layer prepared by the mechanical energy aided aluminizing process with different parameters ceramic balls impact and pack cementation process are mainly composed by Al-rich phase such as Al13Fe4, FeAl3. Which prepared by the former process are stacked by lots of granuliform aluminide, and those are single layers. The elements in aluminizing are homogeneous distribution, and the atomic ratio of Al/ Fe is about 3:1, which is higher than that prepared by mechanical energy aided aluminizing without ceramic balls impact(2.5:1). And the content of aluminum on aluminized layer surface prepared by mechanical energy aided with ceramic balls impact is higher than that by traditional pack cementation process.The hardness of the surface of aluminized layer prepared by mechanical energy aided aluminizing process with ceramic balls impact is 961HV0.2, which is slightly higher than that prepared by pack cementation process is 844.5HV0.2. And the wear volume of which prepared by the former process is 340?m3, which is little more than the latter 282?m3, and the friction coefficient of the aluminized layer prepared by different processes were both maintained at between 0.5 to 0.6. The oxidation mass gain curve of aluminized samples prepared by two kinds aluminizing process at 600? for 100 h both showed a parabolic law, after oxidation, the oxydate on surface of aluminized layer increases apparently more than 20wt%, and there is no oxidation peeling phenomenon, it belongs to the level of entirely oxidation resistance under the condition of medium temperature.At the aluminized temperature 550~650?, the growth rate constant of aluminized layer prepared by mechanical energy aided with ceramic balls impact is about 2 to3 times more than that by traditional pack cementation, and the diffusion activation factor Q is significantly lower than that by the powder pack cementation process. The impact and friction produced by ceramic balls and aluminizing medium particles on the surface of stainless steel led to the roughness increasing, which increased the chance of samples contact with active atoms, so that increased the content of aluminum on the surface of the samples, and promote diffusion of active atoms. What's more, the impact and friction between ceramic balls and aluminizing medium particles, led to the surface defects increased, and formate the fast-track to promote mutual diffusion of the active atoms, so that reduced the diffusion activation factor, and improved the growth rate constant, which accelerate the formation of the aluminized layer.