高能喷丸法实现工业纯铁表面自纳米化

Surface self-nanocrystallization on industrial pure iron by high energy shot peening

运用高能喷丸法(HESP)在工业纯铁表面获得一定厚度的自纳米化层,通过金相显微镜观察、SEM分析、显微硬度测试以及XRD分析对自纳米化层的组织结构与性能进行了表征,重点对自纳米化层厚度、显微硬度分布与喷丸工艺参数之间的关系进行了分析研究。结果表明,采用0.5 MPa喷丸压力,喷丸5 min,即可在工业纯铁表层得到平均晶粒尺寸为58.5 nm,厚度为127μm的自纳米化层。喷丸时间对自纳米化层厚度和晶粒大小的影响大于喷丸压力的影响。在不低于0.5 MPa喷丸压力下,只要保持足够的喷丸时间都可实现工业纯铁表面自纳米化。而在0.6 MPa的喷丸压力下,喷丸14 min可获得最大厚度为148μm的自纳米化层。工业纯铁自纳米化层的显微硬度呈梯度变化,随着距表面距离的增加而连续降低。

A self-nanocrystallized layer was prepared on industrial pure iron by means of high energy shot peening（HESP） method which was successfully used to self-nanocrystallize many metals and alloys.Performance and microstructure of the self-nanocrystallized layer,effects of the peening parameters on depth and microhardness distribution of the layer were investigated through microscope observation,SEM analysis,microhardness test and XRD analysis.Results show that under 0.5 MPa peening pressure and 5 min peening time,a self-nanocrystallized layer with depth of 127 μm and average grain size of 58.5 nm can be obtained.The effect of peening time on the grain size and depth of the self-nanocrystallized layer is bigger than that of the peening pressure.The industrial pure iron can be self-nanocrystallized under not less than 0.5 MPa peening pressure if keeping enough peening time.A self-nanocrystallized layer with a maximum depth of 148 μm can be prepared at 0.6 MPa peening pressure for 14 min.The microhardness of the self-nanocrystallized layer gradually decreases with the distance to the surface.