热处理对激光熔覆GX4CrNi13-4显微组织和力学性能的影响  

Effect of heat treatment on the microstructure and mechanical property of GX4CrNi13-4 manufactured by laser cladding

作　　者：何凌欢 李家民 张华炜 侯娟[1] 田馨妮 黄爱军 HE Linghuan;LI Jiamin;ZHANG Huawei;HOU Juan;TIAN Xinni;HUANG Aijun(School of Materials and Chemistry,University of Shanghai for Science and Technology,Shanghai 200082,China;Monash Center for Additive Manufacturing,Monash University,Notting Hill,VIC 3168,Australia;Department of Materials Science and Engineering,Monash University,Clayton,VIC 3800,Australia;Suzhou Industrial Park Monash Research Institute of Science and Technology,Suzhou 215004,China)

机构地区：[1]上海理工大学材料与化学学院,上海200082 [2]蒙纳士大学增材制造中心,澳大利亚诺丁山3168 [3]蒙纳士大学材料科学与工程系,澳大利亚克莱顿3800 [4]苏州工业园区蒙纳士科技研究院,苏州215004

出　　处：《核技术》2024年第6期99-109,共11页Nuclear Techniques

基　　金：深圳市协同创新科技计划-国际科技合作项目(No.GJHZ20200731095203011)资助。

摘　　要：激光熔覆凭借低成本、高效率被激光再制造领域重点关注,激光熔覆制造的GX4CrNi13-4马氏体不锈钢是一种核电站中应用广泛的结构材料。为改善激光熔覆制件低塑性问题,需进行热处理组织结构调控,改善其力学性能。采用激光熔覆技术制备了GX4CrNi13-4不锈钢样品,对其热处理组织开展调控研究。首先通过热膨胀试验推导出该合金的奥氏体相变开始温度为620℃,作为热处理工艺开发的基准参考温度。分别制定了固溶时效(1050℃保温1 h+550℃保温4 h,简称固溶时效处理)和单时效(620℃保温2 h,简称单时效处理)两种热处理工艺,对比研究了热处理对覆层金属显微组织和力学性能的影响作用。然后采用X射线衍射仪、光学显微镜、扫描电子显微镜、透射电子显微镜对热处理后的显微组织结构和物相分布等进行表征,并对热处理前后的样品进行室温拉伸性能测试。结果表明:激光熔覆GX4CrNi13-4马氏体不锈钢沉积态样品基体组织主要为马氏体/铁素体双相组织,铁素体相呈连续网状结构,沿马氏体晶界析出,此外还存在少量残余奥氏体。经固溶时效热处理后,基体仍主要由马氏体和铁素体组成,但连续网状铁素体发生分解,且出现大量微米级马氏体晶内析出物,这导致材料塑性略有提升,但强度显著下降。对覆层样品进行单时效热处理,由于温度处于奥氏体相转变临界温度,样品中产生了逆变奥氏体相,该相在拉伸过程中引发相变诱发塑性(Transformation Induced Plasticity,TRIP)效应。此外,单时效处理后沿马氏体析出的网状铁素体进一步得到分解,呈离散分布。TRIP效应和铁素体分解的共同作用下,有效改善了激光熔覆GX4CrNi13-4不锈钢的塑性同时使得强度被较好地保持。激光熔覆工艺在修复和再制造领域具有广泛的应用前景,但熔覆过程的高冷却速度、复杂的热循环对材料的组织结构产生�[Background]Laser cladding,recognized for its cost-effectiveness and high efficiency,has become a focal point in the field of laser remanufacturing.GX4CrNi13-4 martensitic stainless steel produced by laser cladding is a widely used structural material in nuclear power plants.[Purpose]This study aims to enhance the mechanical properties of GX4CrNi13-4 martensitic stainless steel,fabricated using laser cladding technology,through different heat treatments that cause microstructure modification.[Methods]The GX4CrNi13-4 stainless steel sample was prepared using laser cladding technology,and its heat treatment microstructure was studied in details.Firstly,thermal expansion experiments identified the onset temperature of austenitic phase transformation of sample at 620°C,serving as a pivotal reference for developing heat treatment schemes.Two distinct heat treatment processes,i.e.,solution treatment plus aging(STPA)at 1050°C for 1 h followed by a similar treatment at 550°C for 4 h and single aging(SA)at 620°C for 2 h,were applied to experiments.The effects of these treatments on the microstructure and mechanical performance of the cladding were comparatively analyzed by using X-ray diffraction(XRD),optical microscopy,scanning electron microscopy(SEM),and transmission electron microscopy(TEM)were employed to characterize the post-treatment microstructure and phase distribution.Tensile tests at room temperature were performed on samples before and after heat treatment.[Results]Experimental results indicate that the as-cladded GX4CrNi13-4 stainless steel exhibits a dual-phase microstructure primarily comprising martensite and ferrite,with continuous network-like ferrite precipitated along martensitic boundaries,accompanied by a minor presence of residual austenite.Post STPA,the matrix still predominantly comprises martensite and ferrite,but the continuous network-like ferrite decomposes,and numerous micrometer-scale transgranular precipitates within the martensite are observed.This led to a slight improvement in plast

关 键 词：马氏体不锈钢 激光熔覆 逆变奥氏体 热处理增韧 热膨胀系数 奥氏体转变温度 

分 类 号：TG142.1[一般工业技术—材料科学与工程] TL374.5[金属学及工艺—金属材料]