返回次数对镍基K4169合金组织及性能的影响

采用50%返回料+50%新料的新工艺熔炼镍基K4169合金,进行了4次返回料的熔炼试验。采用金相显微镜及扫描电镜对新料合金及返回料合金的微观形貌进行了观察,用直读光谱仪对不同返回次数的合金进行了化学成分分析、对其力学和持久性能进行测试,研究了返回料熔炼对合金化学成分、微观组织及力学性能的影响。结果表明:随返回次数增加,化学成分无明显变化,合金的气体含量略呈下降趋势且总含量低于40×10-6,返回料冶炼过程中可不添加B和Zr。K4169合金凝固组织为典型枝晶结构,返回料对K4169合金的铸态枝晶组织没有明显影响。MC型碳化物及Laves相在热处理过程中部分分解,析出针片状δ相,在所有元素中,Nb的偏析最为严重,通过适当延长固溶处理时间可提高元素Nb的分布均匀性和抑制δ相的生成。返回料合金的室温拉伸强度及屈服强度随返回次数增加略有增加,合金的持久寿命较新料合金略有降低,但均明显超过现有技术标准规定的要求。熔炼的返回料合金具有良好的中温塑性,总体上与新料的质量水平相当。返回料合金的铸造性能与新料相当,可以代替新料用于铸件生产。

Effect of Revert Recycle Times on Microstructure and Mechanical Properties of Ni-Based Superalloy K4169

A novel melting process for the Ni-based alloy K4169 was developed using 50 % revert alloy and 50 % green alloy,and the revert alloy was recycled 4 times.The microstructure of green alloy and revert alloy was observed using optical microscopy(OM) and scanning electron microscopy(SEM).The effects of revert recycle times on their chemical composition,mechanical properties and rupture life were investigated by inductive coupling plasma mass analyzer(ICP-MS,JY70 PLUS) and mechanical measurement at various temperatures.The results showed that with the revert recycling time increasing,the chemical composition of the revert alloy was basically stable,with a decrease tendency for gas element contents(total content below 40×10-6),so during the melting process it was not necessary to add B and Zr.It was found that the microstructure of K4169 alloy obtained was a typical dendrite structure.Compared with the green alloy,the dendrite morphology of the revert alloy exhibited no obvious modification.The MC-type carbides and Laves phase would be decomposed during the subsequent heat treatment process,with the formation of needle-like δ phase.Among all the elements,the segregation of Nb was the most serious one and the distribution of Nb in alloy would be improved by appropriate extension of quenching time for the heat treatment process and the δ phase formation consequently was suppressed.The alloy mechanical properties were influenced by the revert recycle times.With the revert recycles increased,the revert alloy tensile and yield strengths at room temperature showed a slight increase tendency,while their creep rupture life was reduced compared with the green alloy.But,the mechanical properties and creep rupture life for these revert alloys were clearly better than the current standard requirements for K4169 alloy.The revert alloy had a good mechanical properties at medium temperature,which was similar to the qualities of green alloy.For the casting performance,both the revert alloy and the green alloy were basically the same and the revert alloy could replace the green alloy for casting.