激光冲击强化对太阳能热发电用渗铝钢显微组织和高温拉伸性能的影响  

Effect of Laser Shock Strengthening on Microstructure and High Temperature Tensile Properties of Aluminized Steel for Solar Thermal Power Generation

作　　者：李微[1,2] 许栋梁 左炉 陈荐 李传常 何建军[1,2] 任延杰 李聪[1,2] 邱玮 张圣德[3] LI Wei;XU Dong-liang;ZUO Lu;CHEN Jian;LI Chuan-chang;HE Jian-jun;REN Yan-jie;LI Cong;QIU Wei;ZHANG Sheng-de(Key Laboratory of Efficient&Clean Energy Utilization,School of Energy and Power Engineering,Changsha University of Science&Technology,Changsha 410114,China;Hunan Province 2011 Collaborative Innovation Center of Clean Energy and Smart Grid,Changsha 410114,China;Japan Electric Power Central Research Institute,Tokyo 240-0196,Japan)

机构地区：[1]长沙理工大学能源与动力工程学院能源与高效清洁重点实验室,长沙410114 [2]清洁能源与智能电网湖南省2011协同创新中心,长沙410114 [3]日本电力中央研究所

出　　处：《表面技术》2019年第1期1-9,共9页Surface Technology

基　　金：国家自然科学基金(51675058);湖南省自然科学基金项目(2018JJ3531);湖南省教育厅科学研究重点项目(16A002);湖南省创新计划项目(2018RS3073)~~

摘　　要：目的研究激光冲击强化前后,渗铝321不锈钢的显微组织变化和高温拉伸行为。方法采用固体粉末包埋渗铝法对321奥氏体不锈钢板材拉伸试样进行渗铝处理,制成渗铝钢,再对渗铝钢中间8 mm?25 mm标距段进行双面激光冲击强化处理,激光波长为1064 nm,单脉冲能量为7 J,脉宽为20 ns,冲击次数为1次和3次,圆光斑直径为2.6～3 mm,搭接率50%,黑胶布为保护层,水为约束层,并评价激光冲击前后渗铝钢表面完整性。对渗铝钢在620下进行高温拉伸试验,获得真应力-真应变曲线、屈服强度、抗拉强度以及断后延伸率,并在扫描电镜下观察拉伸断口微观形貌。结果渗铝钢的表面粗糙度和显微硬度随着激光功率密度和冲击次数的增加而提高。激光冲击强化后的渗铝钢表现出更高的屈服强度、抗拉强度和断后延伸率,其中,以6.59 GW/cm2激光密度三次冲击的渗铝钢的高温拉伸性能最佳。激光冲击强化后的渗铝钢高温拉伸断口表现出韧性断裂特征。结论激光冲击强化后,渗铝钢表面发生明显塑性变形,形成了起伏较大的凹坑和凸台,改变了材料粗糙度。表面晶粒细化、位错运动加剧以及位错增殖使得材料表面硬度和激光冲击硬化影响层深度提高;另外,引入的高幅残余压应力的释放能够抵消外加拉应力,延缓表面裂纹的形核和扩展。激光冲击强化显著改善了渗铝钢力学性能。The work aims to investigate the effects of laser shock peening on the microstructure and high temperature tensile properties of aluminized 321 stainless steel.The aluminizing was carried out to tensile sample of 321 austenitic stainless steel by packed cementation to prepare the aluminized steel.Then the double-side gauge area(8 mm?25 mm)of aluminized steel was performed by laser shock process with different parameters:pulse wave length of 1064 nm,pulse energy of 7 J,pulse width of 20 ns,circular spot diameter of 2.6~3 mm and overlapping ratio of 50%.Black tape was used as the protective layer and water was used as the restraint layer.The surface integrity of aluminized steel was evaluated and then high temperature tensile test was carried out to aluminized steel at 620℃to obtain the true stress-true strain curve,the yield strength,ultimate strength and elongation.The fracture morphology was observed by scanning electron microscopy.The surface roughness and micro-hardness of aluminized steel increased with the increasing of laser power density and impact times.Aluminized steel processed by laser shock exhibited higher yield strength,tensile strength and elongation.The aluminized steel with laser energy density of 6.59 GW/cm^2 and three-times of impact showed the best tensile performance.The high-temperature tensile fracture of aluminized steel strengthened by laser impact exhibited the ductile fracture characteristics.Obvious plastic deformation occurs at the surface of aluminized steel after laser shock,resulting in larger pit and boss and changing the material roughness.Refinement of surface grains,intensive dislocation and increase of dislocation improve the surface hardness and the depth of hardening impact layer by laser shock.In addition,the release of introduced high amplitude residual compressive stress can offset the external tension and delay the formation and extension of surface crack.Therefore,laser shock strengthening improves the mechanical properties of aluminized steel.

关 键 词：激光冲击强化 321奥氏体不锈钢 渗铝 显微组织 高温拉伸 

分 类 号：TG668[金属学及工艺—金属切削加工及机床]