感应加热消除激光直接成形DD4零件裂纹

Elimination of Laser Direct Forming Crack on DD4 Parts by Induction Heating

针对单晶镍基高温合金DD4在激光直接成形过程中熔覆层开裂的问题,利用不同工艺在定向凝固DZ125L基体上成形DD4零件,研究了DD4零件熔覆层的裂纹种类和裂纹特征以及基本工艺参数对DD4零件裂纹率的影响。提出了利用感应加热辅助激光直接成形的方法来消除DD4零件熔覆层裂纹。结果表明,DD4零件熔覆层裂纹分为凝固裂纹和液化裂纹两种,其中绝大多数裂纹为液化裂纹;降低激光功率,增大扫描速度,选取合适的搭接间距和提升量都有利于降低DD4零件熔覆层的裂纹率。试验中通过优化工艺参数,可将DD4零件裂纹率降低至0.230mm/mm^2。裂纹率会随着感应加热温度的升高而下降,感应加热温度为1200℃时裂纹率可降低至0.017mm/mm^2。

Abstract To solve the problem of cladding layer cracking of single-crystal Ni-based superalloy DD4 during the laser direct forming process, DD4 parts are fabricated on the directionally solidified DZ125L substrate by different processes. The kinds and the characteristics of cracks in cladding layers of DD4 parts and the effects of basic process parameters on the crack rate of DD4 parts are investigated. The laser direct forming process which is assisted by induction heating is proposed to eliminate the cladding layer cracks of DD4 parts. The results indicate that the cracks in the cladding layers of DD4 parts mainly include solidification crack and liquidation crack, and most of the cracks are the latter one. Reducing laser power, increasing scanning speed, and choosing appropriate overlapping space and elevation can decrease the crack rate of cladding layers of DD4 parts. The crack rate of the DD4 parts can be reduced to 0. 230 mm. mm 2 by optimizing process parameters. The crack rate of DD4 parts decreases with the elevation of the induction heating temperature, and the crack rate is 0. 017 mm·mm^-2 when the induction heating temperature is 1200℃.