CRDM钩爪不同工艺钴基合金堆焊层组织表征及性能研究

Study on the microstructure and properties of the cobalt-base alloys surfacing layer of the CRDM claws with different technologies

控制棒驱动机构(Control Rod Drive Mechanism,简称CRDM)钩爪部件形状复杂精密,是压水堆一回路的运动执行部件,其销轴孔与齿部钴基合金堆焊层组织与性能要求极高。通过激光熔敷、氧乙炔焊两种工艺试验,获得了满足设计要求的工艺参数。对两种工艺获得的钴基合金堆焊熔敷层进行组织表征与分析,比较两种工艺熔敷层的宏观与微观形貌差异,测试与对比分析熔敷层显微硬度,对熔敷层界面处的Co、Cr、Fe等元素进行了线扫描,通过Fe元素的分布分析两种不同熔敷层稀释率与硬度差异的关系。两种堆焊层均未观察到微裂纹、夹杂、气孔、未熔合等缺陷,激光熔敷钴基堆焊层晶粒最细,因细晶强化作用,其显微硬度也最高。

The shape of the claws of the control rod drive mechanism(CRDM)is complex and precise,the claws are the motion actuator in primary circuit of the pressurized water reactor,the surfacing layer of the pin hole and claws tooth is welded by the cobalt-base alloys,so the microstructure and properties of the surfacing layer have a great influence on the CRDM.The appropriate technological parameters that meet the design requirements are obtained by the oxyacetylene welding technology and laser welding technology tests.In addition,the microstructure characterization and analysis of the surfacing deposition layers of the cobalt-base alloys obtained by theses two welding technologies are carried out,the differences of the macrostructures and microstructures of the deposition layers of these two technologies are compared,and the micro hardness of the deposition layer is tested are contrastively analyzed.The elements Co,Cr and Fe of the deposition layer are tested by the line scanning.The relations between the dilution rate and hardness difference of these two different deposition layers are analyzed through the distribution of element Fe.No micro crack,inclusion,air hole,lack of fusion and other defects are observed in these two different surfacing layers.Because of the fine grain strengthening effect,the grain in the surfacing layer of cobalt-base alloys by laser welding is the most fine,and the micro hardness is also the highest in the surfacing layer.