超超临界电站用Inconel 740镍基合金的组织稳定性及其改型研究

Structural Stability and Improvement of Inconel Alloy 740 for Ultra Supercritical Power Plants

利用微观组织分析和化学相分析的综合方法研究了超超临界电站锅炉过热器管材用镍基高温合金Inconel 740在服役温度范围长期时效下的组织稳定性,并基于热力学模拟计算对合金的成分进行调整和改型.结果表明:合金的组织不稳定性主要表现在高温时强化相γ′相急剧长大、晶内和晶界η相以及晶界G相的形成;通过调整Al、Ti含量和降低Si含量研制了改型合金,改型合金γ′相的稳定温度得到提高,在750℃和800℃长达5 000 h时效后晶界没有出现η相和G相,表现出良好的组织稳定性.

Structural stability of high-temperature Inconel alloy 740 for boiler superheater tubes of ultra supercritical（USC） power plant was studied after long-term aging using microstructure and micro-chemical phase analysis.Based on thermodynamic calculation,the chemical composition of the alloy was modified.Experimental results show that the most important microstructure instabilities at high temperatures are found to be γ′ coarsening,γ′ to η transformation and G phase formation.By adjusting the Al,Ti content and lowering the Si content,the phase stabilization temperature of the modified alloy is improved without η and G phase formation after aging at 750 ℃ and 800 ℃ for 5 000 h,indicating better microstructure stability of the modified alloy.