汽轮机叶片的方形光斑激光多层交错冲击均匀强化及抗腐蚀行为

To solve the challenge of uniform strengthening in the edge region of the ultra-supercritical steam turbine blade, the uniform strengthening mechanism of steam turbine blade subjected to square-spot laser shock peening (LSP) with stagger multilayer and its anti-corrosion behaviour are investigated in the present proposal. This research can meet the need of the longlife and reliable service for ultra-supercritical steam turbine. The following issues will be focused: .The first is to investigate the time and space distributions of the square-spot and the loading feature to metallic material, develop the distribution model of residual stress as functions of sheet depth and surface curvature, achieve strengthening theory and technic criteria of square-spot LSP with stagger multilayer, and control the plastic deformation of complicated surface subjected to the uniform strengthening treatment. The second is to describe the distribution characteristics and the relaxation process of deeper and uniform residual stress field, and its inhibition mechanism of corrosion element diffusion, and gain the corrosion crack growth law in the action of environment and stress. The last is to characterize gradient microstructure in depth direction, and grain size distribution, gain the grain refinement mechanism or surface nanocrystallization mechanism, develop the strong correlations between the technological parameters, microstructure and anti-corrosion performance in system, and reveal the anti-corrosion life extension mechanism under the combination effect of residual stress and grain size generated by square-spot LSP with stagger multilayer. .The above research involves many new scientific issues, and these research achievements can not only enrich and develop the uniform strengthening theory of complicated surface, and improve the corrosion resistance of steam turbine blade, but also provide the scientific basis for the manufacturing technology of ultra-supercritical steam turbine.

面向超超临界大型汽轮机长寿命可靠运行的需求，针对低压过渡区叶片边缘均匀强化难题，开展方形光斑激光多层交错冲击均匀强化及抗腐蚀行为研究。主要包括：⑴研究方形光斑时空分布及加载特性，探索脉冲激光与材料相互作用机理，建立以板料厚度、表面曲率为特征参量的塑性变形分布模型，获得方形光斑激光冲击均匀强化理论和工艺准则，实现复杂表面塑性变形的精确控制；⑵描述方形光斑激光冲击诱导的较深均匀残余应力场分布特性、释放过程以及对腐蚀元素扩散的抑制机制，阐明环境-应力交互作用下腐蚀裂纹萌生和扩展规律；⑶微观表征叶片表层梯度结构和晶粒尺寸分布，获得激光冲击叶片材料的晶粒细化/纳米化机制，建立工艺参数-微观结构-抗腐蚀性能的强关联关系，揭示残余应力/晶粒尺寸协同的抗腐蚀行为。相关内容涉及众多全新科学问题，研究成果可以丰富和发展复杂表面均匀强化理论，提高汽轮机叶片抗腐蚀性能，为提升超超临界汽轮机制造水平提供科学依据。

面向超超临界大型汽轮机长寿命可靠运行的需求，针对低压过渡区叶片边缘均匀强化难题，开展了方形光斑激光多层交错冲击均匀强化及抗腐蚀行为研究。主要取得了以下进展：① 成功研制了基于五分透镜的方形光斑调制系统，发明了方形光斑多层叠加交错冲击强化工艺，实现了叶片类零件的大面积冲击均匀强化；② 对于体心四方(BCT)结构的2Cr13马氏体不锈钢，多层激光冲击强化诱导材料深度方向上梯度纳米结构，激光冲击强化也导致了原始粗大碳化物碎化和纳米碳化物析出，揭示了不同冲击层诱导的疲劳性能提升机制；③ 大面积激光冲击强化有效降低材料的腐蚀疲劳裂纹扩展速率，从而显著提升了马氏体不锈钢腐蚀疲劳寿命,同时含氯浓度与腐蚀疲劳寿命成反比，在此基础上揭示了基于应力场深度和垂直方向的2Cr13马氏体不锈钢抗腐蚀疲劳的物理机制；④ 建立了2Cr13马氏体不锈钢在不同pH值NaCl溶液中的腐蚀疲劳行为与激光脉冲能量的关系，从微观角度揭示了激光脉冲能量对2Cr13马氏体不锈钢腐蚀疲劳性能的影响机理；⑤ 激光冲击强化明显提升镁-铝-锰合金在浓度为3.5%的NaCl腐蚀溶液中的抗电化学腐蚀性能，随着冲击层数的增加，其抗电化学腐蚀性能得到进一步改善，建立了含氯溶液浓度、冲击层数和腐蚀时间与电化学腐蚀参数之间的物理模型；⑥ 激光冲击在4145钢的表层产生了残余压应力场，在一定程度上抑制了氧化膜的破坏，高温腐蚀性能得到提高，虽然不能阻止金属表面发生氧化发生，但是残余压应力平衡了氧化膜的拉应力，抑制表面氧化膜的脱落，从而提高了高温Y接头的使用寿命。.在项目执行期内，圆满完成计划任务书的各项任务。研究成果获2019年江苏省科学技术奖一等奖1项，主要研究成果发表论文14篇，其中SCI收录10篇，EI收录4篇(不含SCI收录)。获美国授权发明专利3件、中国授权发明专利4件，申请美国发明专利1件，获得软件著作权2件。参加国际/国内会议交流15次(44人次)，作邀请报告3次。研究执行期内，项目组获得省级人才项目2人次、省级青蓝工程骨干教师计划1人次，1人当选为第一届全国高能密度热处理学术会议委员，培养博士研究生1名、硕士研究生6名，获省优博1篇、省优硕1篇。