NiFe基合金激光增材制造热裂纹形成机理及调控  

Mechanism and elimination of hot cracks in laser additive manufacturing of NiFe based superalloy

作　　者：王帅 付立铭[2] 袁勇[3] 尹宏飞[3] 徐济进[1,2] 谷月峰 WANG Shuai;FU Liming;YUAN Yong;YIN Hongfei;XU Jijin;GU Yuefeng(Shanghai Key Laboratory of Materials Laser Processing and Modification,Shanghai Jiao Tong University,Shanghai,200240,China;Shanghai Jiao Tong University,Shanghai,200240,China;Xi’an Thermal Power Research Institute Co.,Ltd.,Xi’an,710032,China)

机构地区：[1]上海交通大学,上海市激光制造与材料改性重点实验室,上海200240 [2]上海交通大学,上海200240 [3]西安热工研究院有限公司,西安710032

出　　处：《焊接学报》2022年第5期8-13,I0003,I0004,共8页Transactions of The China Welding Institution

基　　金：国家自然科学基金资助项目(52071212)。

摘　　要：针对NiFe基高温合金增材制造过程易出现热裂纹的问题,开展该合金热裂纹形成机理的研究,提出通过层间温度控制以及粉末氮化的方法,降低NiFe基高温合金激光增材过程中的热裂纹敏感性.结果表明,热裂纹的出现主要是由于元素偏析以及热应力所引发的,热裂纹位置大多在大角度晶界处,这是由于大角度晶界中能量较高,在冷却过程中,晶界内液膜的存贮时间较长,从而造成偏析加剧.当层间温度较低,冷却速度加快,能够减少合金中有害碳化物的长大,降低了大角度晶界比例,从而抑制热裂纹的出现.粉末预氮化通过预先将Ti, Nb等元素进行氮化,形成稳定氮化物,在抑制开裂敏感性元素偏析的同时增加了形核点,促进晶粒细化,从而降低该合金的热裂纹敏感性.To solve the problem of hot cracking in laser additive manufacturing process of NiFe based superalloy, the formation mechanism of hot crack was investigated, and the method of interlayer temperature control and powder nitriding to reduce the sensitivity of hot crack was proposed in the laser additive process of NiFe based superalloy. The results show that the occurrence of hot crack is mainly caused by element segregation and thermal stress. Most of the hot cracks are located at the high angle grain boundary, which own higher grain boundary energy to extend existing time of liquid film in grain boundaries during the cooling process, so the obvious segregation phenomenon occurs. When the interlayer temperature is lower, the cooling rate is faster, which can reduce the growth of harmful carbides in the superalloy. The proportion of high angle grain boundary is reduced, and the probability of hot crack is reduced further. Another method is to form stable nitrides by pre-nitriding Ti, Nb elements in the powder, which inhibits element segregation, increases the nucleation points and promotes grain refinement, therefore, the hot crack sensitivity of the superalloy is decreased.

关 键 词：NiFe基高温合金 增材制造 热裂纹 层间温度 粉末氮化 

分 类 号：TG456.7[金属学及工艺—焊接] TG665