An Improved Surface Treatment Process of 304 Stainless Steel Based on Low-Temperature Chromizing and Ultrasonic Vibration Extrusion

The ultrasonic vibration extrusion process is a widely used surface treatment process of stainless steel, e.g., 304 stainless steel, to improve the surface quality and increase hardness and wear resistance. However, for high-hardness 304 stainless steel, the traditional process, i.e., a single ultrasonic vibration extrusion process, does not fulfil its application requirements. To cope with this problem, this paper proposes an improved surface treatment method based on low-temperature chromizing and ultrasonic vibration extrusion to obtain the expected surface quality of 304 stainless steel. Using orthogonal design and multivariate regression, the influence of ultrasonic impact parameters on the surface integrity of 304 stainless steel was studied in this work. Finally, the experimental results show that the hardness of the surface processed by the proposed method is increased by about 2.55 times compared with the ultrasonic vibration extrusion process, and the surface roughness of the composite process is reduced by an average of 60.8% compared with that of unfinished surface. In addition, the optimal combination of process parameters is obtained: the spindle speed of 240 rpm, the feed of 0.1 mm/r, and the static extrusion of 40 μm, which can provide the optimal process parameter support for the surface treatment of 304 stainless steel.