表面机械研磨处理后316L不锈钢的表层结构及硬度的热稳定性

THERMAL STABILITY OF STRUCTURE AND HARDNESS OF THE SURFACE LAYER OF 316L STAINLESS STEEL AFTER SURFACE MECHANICAL ATTRITION TREATMENT

对316L不锈钢进行表面机械研磨处理(SMAT),获得表面为纳米晶、晶粒尺寸沿厚度方向逐渐增大的梯度组织.对SMAT前、后样品进行不同温度和时间的真空退火.结果表明:当退火温度低于0.5Tm(Tm为熔点)时,梯度组织中晶粒尺寸未发生明显变化,只是在表面纳米晶层及其相邻的亚微晶层上因残余应力释放而发生了马氏体相变,对应的硬度沿深度分布也未见明显的改变;当退火温度高于0.5Tm时,梯度组织发生回复和再结晶,加之残余应力大幅度下降,使硬度明显下降.与退火温度相比,退火时间对梯度组织和硬度的影响不大.

After surface mechanical attrition treatment (SMAT) for 316L stainless steel, a gradient structure in its surface layer with grain size from nano-scale to micro-scale was obtained. The samples before and after the SMAT were annealed in vacuum at different temperatures for different durations, and the structural evolution as well as the hardness and the residual stress variations along the depth were analyzed. Experimental results show that when the annealing temperature is lower than 0.5T(m) (T-m is the melt point), no obvious change can be found for the grain size in the gradient structure, except the martensite transformation in the affected layer due to the release of residual stress, and the hardness distribution along the depth remains unchanged. When the annealing temperature is higher than 0.51(m), recovery, recrystallization and sharp drop of the residual stress occur in the gradient structure, which induce significant reduction of the hardness along the depth. The effect of annealing duration on the structure and property of the SMAT sample is less important comparing with the annealing temperature.