The present study proposes a novel method, i.e., combined severe shot peening (SP) and reversion annealing treatment, to grain-refine the surface layers of 304L austenitic stainless steel. Steel specimens were shot-peened at 0.7 MPa for 30 min, introducing 40% vol. α′ martensite, and then were annealed at 700 or 800 °C for different durations (30 s). As annealing reversed α′ martensite to austenite, the obtained surface layers consist of fully austenitic ultrafine grains. The smallest grain size obtained is about 500 nm at the top surface. SP elevates the microhardness to more than 500 HV. Although the grain-refined surface layers produced by the combined method are not as hard as that treated by only SP, they are harder (e.g., the specimen annealed at 700 °C for 30 s using a heating rate of 50 °C/s exhibited a peak microhardness of 400 HV) than the untreated surface layer (225 HV) due to grain refinement. Moreover, due to the absence of α′ martensite, they have higher corrosion resistance in H₂SO₄ solution than that treated by only SP.

中文翻译：

---

严重喷丸强化和回火退火相结合处理对304L不锈钢的表面晶粒细化

本研究提出了一种新的方法，即结合严格的喷丸处理（SP）和回火退火处理，以细化304L奥氏体不锈钢的表面层。钢试样在0.7 MPa下喷丸处理30分钟，引入40％的体积。α'马氏体，然后在700或800°C退火不同的持续时间（30 s）。随着退火将α'马氏体反转为奥氏体，获得的表面层由完全奥氏体的超细晶粒组成。所获得的最小晶粒尺寸在顶表面处为约500nm。SP将显微硬度提高到500 HV以上。尽管通过组合方法生产的晶粒细化表面层不如仅通过SP处理的表面坚硬，但它们更坚硬（例如，由于晶粒细化，与未处理的表面层（225 HV）相比，以50°C / s的加热速率在700°C退火30 s的样品表现出的峰值显微硬度为400 HV。而且，由于不存在α'马氏体，因此在H中具有较高的耐腐蚀性₂ SO ₄溶液比仅SP处理的溶液要多。