摘要
针对激光熔覆层残余应力过大导致变形、开裂的问题,采用激光冲击技术对Fe314合金熔覆层进行了表面冲击处理,分析了熔覆层残余拉应力分布形式及消除机理。结果显示,激光熔覆时采用相对较大的激光比能量,即慢扫描速度、小光斑直径和低送粉速率工艺可有效降低熔覆层残余拉应力。而激光冲击大幅降低了熔覆层残余拉应力,随着冲击次数提高,熔覆层拉应力减小,但拉应力降低幅度呈逐渐减弱趋势。冲击波力学效应引发的极大应变率使熔覆层表层发生微塑性变形,形成压应力场,大幅抵消熔覆层初始态残余拉应力。材料压缩变形时在γ-Fe晶粒内萌发大量位错线,位错发生多系滑移并相互缠结形成位错墙,引发细晶强化作用。
Due to the thermal deformation and crack of laser cladding layers induced by residual stress, a treatment of laser shock processing （LSP） is performed to remove the residual stress of Fe314 alloy cladding layer, its mechanics and residual stress distribution are investigated as well. Results show that residual stress can be removed significantly when a high specific energy of laser cladding comprised of slow scanning speed, small spot size and low powder feed rate is adsorbed by melt pool. Furthermore, LSP decreases the residual stress, and with the number of LSP increasing, the residual stress of cladding layer descends gradually while the removing capability attenuates. The mechanics of variation show that a micro-plastic deformation appears on the Fe314 cladding layer surface, which is induced with a huge strain rate of shock wave. A compression stress field is formed and removes the tensile stress of cladding layer. It is observed that mass dislocation lines emerge in the y-Fe grain due to LSP. Then a dislocation wall is formed and separates one grain into several subgrains. Eventually, the effect of grain refinement is occurred in the Fe314 alloy cladding layer.
出处
《中国激光》
EI
CAS
CSCD
北大核心
2013年第10期97-102,共6页
Chinese Journal of Lasers
基金
总装"十二五"预研项目(51327040401)
国家973计划(2011CB013403)
关键词
激光技术
激光熔覆
激光冲击
残余应力
晶粒细化
laser technique laser cladding laser shock processing residual stress grain refinement
