DD6镍基单晶高温合金激光重熔区杂晶的形成机制研究  

Formation Mechanism of Stray Grain in Laser Remelting Zone of DD6 Nickel⁃Based Single Crystal Superalloy

作　　者：王慧君 郭鹏飞 耿建峰 许建军 林鑫[3] 于君[3] 兰红波[1] 杨光 黄卫东[3] Wang Huijun;Guo Pengfei;Geng Jianfeng;Xu Jianjun;Lin Xin;Yu Jun;Lan Hongbo;Yang Guang;Huang Weidong(Shandong Engineering Research Center for Additive Manufacturing,Qingdao University of Technology,Qingdao 266520,Shandong,China;Analytical&Testing Center,Northwestern Polytechnical University,Xi’an 710072,Shaanxi,China;State Key Laboratory of Solidification Processing,Northwestern Polytechnical University,Xi’an 710072,Shaanxi,China;School of Mechatronics Engineering,Shenyang Aerospace University,Shenyang 110136,Liaoning,China)

机构地区：[1]青岛理工大学山东增材制造工程技术研究中心,山东青岛266520 [2]西北工业大学分析测试中心,陕西西安710072 [3]西北工业大学凝固技术国家重点实验室,陕西西安710072 [4]沈阳航空航天大学机电工程学院,辽宁沈阳110136

出　　处：《中国激光》2024年第10期277-289,共13页Chinese Journal of Lasers

基　　金：山东自然科学基金(ZR2020ZDD04);国家自然科学基金(U22A20189,52005280)。

摘　　要：研究了DD6镍基单晶高温合金在不同功率下重熔区内部杂晶的形成机制。碳化物的形成导致固液界面塌陷,进而诱导杂晶的形成;熔池顶部杂晶的产生主要与温度梯度、固液界面的迁移速率有关。激光功率升高导致温度梯度降低,进而诱导柱状晶向等轴晶转变(CET);转向枝晶交汇处杂晶的产生是由枝晶交汇处的温度梯度比其他地方小以及温度梯度方向改变引起的。热应力数值模拟结果表明:低激光功率下的热输入可以有效提高温度梯度并有效降低残余应力水平,有利于抑制单晶修复过程中杂晶的形成。该研究可为单晶修复过程中杂晶的抑制提供理论和实验支撑。Objective Nickelbased singlecrystal superalloys are widely used in the manufacture of singlecrystal turbine blades in the combustion chambers of aircraft engines owing to their excellent hightemperature mechanical properties.However,these components often suffer from severe damage,such as edge erosion,cracking,and pitting,owing to the harsh operating conditions,including high temperatures and pressures,requiring repairs to extend their service life.Laser additive manufacturing technology has garnered significant attention for repairing nickelbased singlecrystal superalloys owing to its unique advantages,including controllable heat input,the ability to fabricate complex structures,and reparability.However,the appearance of grain defects during the repair process may lead to serious failure phenomena,such as crack propagation and component fracture,during component operation,thereby posing potential risks to the safety and reliability of aircraft engines.Therefore,this study selected a DD6 secondgeneration nickelbased singlecrystal superalloy as the substrate material and used lasers with powers of 1200 and 1500 W to remelt the substrate,revealing the mechanisms of stray grain formation at the fusion line,top of the molten pool,and at the intersection of the dendrites,thereby providing a theoretical basis and technical support for the laser additive repair of nickelbased singlecrystal superalloys.Methods This study employed a DD6 nickelbased singlecrystal hightemperature alloy prepared via directional solidification as an experimental substrate material.Subsequently,a laser cladding additive manufacturing device equipped with a 2 kW German Rofin fibercoupled semiconductor laser was utilized.The process parameters included laser powers of 1200 and 1500 W,a scanning rate of 3 mm/s,and a spot diameter of 4 mm for the singletrack remelting experiments on the substrate(001)crystal surface.To prevent sample oxidation during remelting,argon gas was used as a protective gas at a flow rate of 10 L/min.The dendritic morpholo

关 键 词：镍基单晶高温合金 杂晶 单晶修复 激光重熔 

分 类 号：TG14[一般工业技术—材料科学与工程]