旋转加速喷丸处理18CrNiMo7-6钢的微观结构与力学性能

Microstructure and Mechanical Properties of 18CrNiMo7-6 Steel Processed by Rotationally Accelerated Shot Peening

本研究首次采用一种高效率、低成本的大塑性变形技术——旋转加速喷丸技术(Rotationally accelerated shot peening)对正火后高温回火的18CrNiMo7-6钢进行表面纳米化处理,利用光学显微镜、扫描电子显微镜、电子背散射衍射技术、硬度测试以及拉伸测试等对不同喷丸参数的样品进行了微观组织和力学性能的表征。结果表明,旋转加速喷丸能够成功地在材料表面制备出梯度结构,从样品表面到芯部具有明显的显微组织梯度和硬度梯度;调节喷丸速度可以有效地调控材料显微组织,长时间喷丸易萌生微裂纹;在喷丸速度为40m/s、喷丸时间为5min的条件下处理,样品的表面完好,屈服强度提高了57%,达到512 MPa。

In the present work,normalized and high temperature tempered 18 CrNiMo7-6 steel was firstly subjected to rotationally accelerated shot peening（RASP）processing,which was a low-cost and efficient severe plastic deformation（SPD）technique to produce nanostructured surface-layers of metals.The microstructure of the steel after RSAP processing was characterized by optical microscopy（OM）,scanning electron microscopy（SEM）,electron back-scattered diffraction（EBSD）techniques,and the mechanical properties were analyzed by microhardness measurements and tensile testing.Simultaneously,the effects of RASP parameters on the microstructural evolution and mechanical properties were analyzed.It is found that RASP successfully produced a steel with structural gradient and it had a obviously microhardness gradient form surface to the inner.Varying the shot peening velocity was an effective way to control the microstructure,while micro-cracks formed easily at the long shot peening time.With a peening velocity of 40 m/s and a peening time of 5 min,the sample had a harden surface without defects and the yield strength was improved by57%to 512 MPa.