增压涡轮用K424高温合金组织特征及热裂倾向性  

Microstructure and susceptibility to hot tearing of K424 nickel-based superalloys for turbocharger turbine wheels

作　　者：赵展[1] 董建新[1] 张麦仓[1] 郑磊[1] 姚志浩[1] 

机构地区：[1]北京科技大学材料科学与工程学院,北京100083

出　　处：《工程科学学报》2016年第10期1429-1437,共9页Chinese Journal of Engineering

摘　　要：针对K424精密铸造增压涡轮叶片出现的热裂问题,采用组织观察和计算模拟的方法,分析增压涡轮用K424合金特性以及涡轮叶片铸造中出现热裂的原因,并对比K418合金提出合金热裂倾向性的影响因素以及减少热裂的建议.结果表明,铸造增压涡轮热裂倾向性与合金特性及铸件特性等有关.K424合金中Al和Ti元素含量较高,导致合金中共晶组织含量多且尺寸大,与K418合金相比,热裂倾向性较大;另一方面,由于铸件叶片位置厚度小且曲率变化大,易形成应力集中,导致热裂.为减小热裂倾向性,需控制K424合金中Al和Ti元素含量并选择合理的工艺参数.Hot tearing tends to occur when K424 superalloy is used for a turbocharger turbine wheel. To solve this problem,the alloy characteristics of K424 and K418 superalloys and the factors impacting the susceptibility to hot tearing were studied by microstructure observations and casting simulations. The research proposed the main factors which affected the susceptibility to hot tearing and also the method to reduce hot tearing in the turbine wheel. It is found that the susceptibility to hot tearing of the turbine wheel is influenced by both the alloy characteristics and casting characteristics. K424 superalloy shows a higher susceptibility to hot tearing when compared with K418. Because of high amount of aluminum and titanium in K424 superalloy,the size and the amount of γ ＋ γ＇eutectics increase,resulting in more prior forming and propagating areas of hot tearing. On the other hand,due to a smaller thickness and a larger curvature change in the blade margin of the turbine wheel,the uneven distribution of the thermal stress is induced in the end of the solidification process,which leads to hot tearing in this paper. In order to decrease the susceptibility to hot tearing of the turbine wheel,the contents of aluminum and titanium should be controlled,and the reasonable technological parameters of casting should be set to ensure the final effect.

关 键 词：镍基高温合金 力学性能 组织特征 凝固 

分 类 号：TG132.3[一般工业技术—材料科学与工程] TG146.15[金属学及工艺—合金]