激光沉积修复GH738合金时效热处理组织及性能研究

Study on Aging-treatment Microstructure and Properties of GH738 Alloy by Laser Deposition Repair

摘要:

研究了双极时效热处理对激光沉积修复GH738合金显微组织及力学性能的影响。结果显示：沉积态显微组织为典型的外延柱状枝晶，枝晶间距为约10 μm。经过时效处理后，修复区组织开始长大、合并。沉积态未发现γ＇相，枝晶间存在立方状的MC型碳化物，枝晶干存在颗粒状M23C6型碳化物。经双级时效处理后，修复区析出γ＇相：稳定化温度为820℃时，γ＇相平均尺寸约为37nm，碳化物在晶界处呈断续状析出。随着稳定化温度升高，γ＇相及碳化物尺寸均有所增大，其中稳定化温度为840 ℃时，γ＇相平均尺寸约为76 nm，碳化物呈项链状析出；稳定化温度为860℃时，γ＇相平均尺寸无明显增大，部分γ＇相发生明显粗化，尺寸达到150 nm，晶界处碳化物开始呈包膜状析出。力学性能测试结果显示：时效处理后试样抗拉强度明显提高，随着稳定化温度升高，抗拉强度先升高后降低，断后伸长率不断降低。

Abstract:

The effects of bipolar aging heat treatment on the microstructure and mechanical properties were studied on GH738 alloy repaired by laser deposition repair technology.The results show that :the microstructure of repair area present typical characteristics of the epitaxial growth of columnar crystals and the dendrite spacing is about 10μm.After the aging treatment, the repair area begins to grow and merge .The results of SEM analysis show that :There is no γ＇appear at the as-deposited , and the cubic MC type carbide is formed at the interdendritic, and the M23C6 type carbide at the dendrite arm ; After the aging treatment, γ＇phase precipitated at the repair area: γ＇phase with an average size of 37nm was found in the repair area, and the carbide precipitates in the grain boundary with the character of discontinued when the temperature of the stabilization step is 820℃; With the increase of the stabilization temperature, the size of the γ＇ and carbide increases ;When the temperature is 840℃, the average size of the γ＇is about 76nm, and the carbide is precipitated in the form of necklace ;Adding the temperature of the stabilization step to 860℃ , the average size of the γ＇does not increase obviously, and part of the γ＇ of is obviously coarsening and the size reach 150nm, meanwhile the carbides at the grain boundaries begin to form the closed. The results of mechanical property show that :the tensile strength of the sample increases obviously after aging treatment,and with the increase of the temperature, the tensile strength increases first and then decreases, and the elongation decreases continuously.