The aluminized layer of 321 stainless steel was treated by laser shock processing (LSP). The effects of constituent distribution and microstructure change of the aluminized layer in 321 stainless steel on creep performance at high temperature were investigated. SEM and EDS results reveal that aluminized coating is mainly composed of an Al2O3 outer layer, the transition layer of the Fe-Al phase, and the diffusion layer. Additionally, LSP conducted on coating surface not only improves the density of the layer structure, resulting in an increment on the bonding strength of both infiltration layer and substrate, but also leaves higher residual compressive stress in the aluminized layer which improves its creep life effectively. Experimental results indicate that the microhardness of the laser-shocked region is improved strongly by the refined grains and the reconstruction of microstructures. Meanwhile, the roughness and microhardness of aluminized steel are found to increase with the laser impact times. On the other hand, the intermetallic layers, whose microstructure is stable enough to inhibit crack initiation, reinforce strength greatly. The anticreep life of aluminized sample with three times LSP was increased by 232.1% as compared to aluminized steel, which could attribute to the increased dislocation density in the peened sample as well as the decrease of creep voids in size and density.

中文翻译：

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激光冲击加工和镀铝对太阳能热发电用321不锈钢组织和高温蠕变性能的影响

321不锈钢镀铝层采用激光冲击加工（LSP）处理。研究了321不锈钢渗铝层的成分分布和组织变化对高温蠕变性能的影响。SEM和EDS结果表明渗铝涂层主要由Al2O3外层、Fe-Al相过渡层和扩散层组成。此外，在镀层表面进行LSP不仅提高了层结构的密度，使渗层与基材的结合强度增加，而且在镀铝层中留下了更高的残余压应力，有效地提高了其蠕变寿命。实验结果表明，细化晶粒和微观结构的重建大大提高了激光冲击区域的显微硬度。同时，发现镀铝钢的粗糙度和显微硬度随着激光冲击次数的增加而增加。另一方面，金属间化合物层的微观结构足够稳定以抑制裂纹萌生，大大增强了强度。与渗铝钢相比，3倍LSP渗铝试样的抗蠕变寿命提高了232.1%，这可能归因于喷丸试样中位错密度的增加以及蠕变空隙尺寸和密度的减小。其微观结构足够稳定以抑制裂纹萌生的金属间化合物层大大增强了强度。与渗铝钢相比，3倍LSP渗铝试样的抗蠕变寿命提高了232.1%，这可能归因于喷丸试样中位错密度的增加以及蠕变空隙尺寸和密度的减小。其微观结构足够稳定以抑制裂纹萌生的金属间化合物层大大增强了强度。与镀铝钢相比，3倍LSP镀铝试样的抗蠕变寿命提高了232.1%，这可能归因于喷丸试样中位错密度的增加以及蠕变空隙尺寸和密度的减小。