W元素对单晶合金TLP扩散焊微观组织与性能的影响

Effect of tungsten on microstructure and mechanical properties of nickelbased single crystal superalloy TLP diffusion bonding joints

为了研究W元素在单晶合金TLP扩散焊过程中的作用机制,采用两种自主设计的镍基钎料钎焊DD6单晶高温合金,分析了W元素对焊缝显微组织和高温性能的影响.结果表明,含W钎料在DD6钎焊时的等温凝固过程较缓慢,在1 220℃钎焊120 min后才可完成等温凝固,不含W钎料所形成的焊缝存在骨架状富Cr,Ni和W的化合物,而添加W元素后焊缝中主要存在块状W,Cr和Ni化合物,钎焊30 min后,不含W钎料所形成的焊缝性能较高,随着钎焊时间的延长,两种钎料的接头高温抗拉强度均明显提升,且含W钎料的提升速率高于不含W钎料,表明在焊缝完成等温凝固后,W元素对焊缝具有明显的强化作用.采用含W钎料的DD6单晶焊缝1 000℃的高温强度可达到639 MPa,约为母材强度指标的90%.

Two designed Ni-based filler alloys were used to join DD6 single crystal superalloy to investigate the function mechanism of tungsten in the TLP diffusion bonding process of single crystal superalloy.The effects of tungsten on the joint microstructure and mechanical properties were investigated.The isothermally solidified process of brazing alloy containing tungsten conducts slowly.After brazing for 30 min,the joint of brazing alloy without tungsten exhibits higher elevated temperature strength.With the extending of holding time,the elevated temperature strength of both joint increase obviously,where the increase value of joint for brazing alloy with tungsten is higher.It indicates the strengthening effect of tungsten on the joint after isothermal solidification.The elevated temperature strength of DD6 single crystal joint at 1000℃reached 639 MPa after brazing for 120 min with Ni-Cr-Co-Ta-Al-W-B brazing alloy,which is 90 percent of DD6 base material.