单晶涡轮叶片长期服役组织演化及性能退化分析

Metallographic Structure Evolution and Mechanical Property Degradation Analysis of Single Crystal Turbine Blades after Long-Term Service

摘要:

为对单晶涡轮叶片长时服役后的显微组织损伤及力学性能退化程度进行评价，分别选用服役时间为25000h和50000h的燃气轮机用高压涡轮叶片，截取叶身中部材料进行组织定量表征和显微硬度测试。定量测算了不同服役时间和不同位置的γ"相尺寸、体积分数，二次γ"相尺寸，基体通道宽度，并进行了维氏硬度测试。结果表明：同一服役时间不同位置γ"相尺寸粗化程度不同，前缘、尾缘高温区γ"相尺寸大于叶盆、叶背处，而体积分数稍小于其他两处；服役50000h的叶片γ"相尺寸大于相同位置处服役25000h叶片，体积分数呈相反规律；部分位置存在二次γ"相析出现象，二次γ"相析出位置基体通道宽度明显增加，经1100℃/2h空冷/炉冷实验验证，二次γ"相析出与工作高温及冷却方式有关；尾缘服役异常高温区出现TCP相，该相富含W、Re元素，经分析为μ相；不同服役时长前缘、尾缘位置显微硬度均下降明显，且显微硬度下降与γ"相尺寸增大呈负相关、体积分数减少呈正相关关系，γ"相尺寸、体积分数可作为本材料损伤评价参量。

Abstract:

In order to evaluate the damage of microstructure and the deterioration of mechanical properties after long-term service of single crystal turbine blades. This paper selects the high pressure turbine blades of gas turbines that have served 25000h and 50000h respectively. The material in the middle of the blade body was selected for metallographic structure quantitative analysis and microhardness test. The γ" phase size, γ" phase volume fraction, secondary γ" phase size, γ matrix channel width with different service time and at different positions were measured. And the Vickers hardness were tested. The results show that the γ" phase size of different positions in the same leaf is different; The γ" phase size at the leading edge and the trailing edge which working at high temperature is larger than Pressure side and Suction side;however, the γ" phase volume fraction is slightly smaller than the other two; the γ" phase size of serviced 50,000h blade is greater than the serviced 25000h γ" phase size at the same position; the volume fraction is in the opposite order; secondary γ" phase appears in some positions, the width of the base channel is significantly increase at the secondary γ" phase precipitation position; it is verified by 1100 °C/2h-air+cooling/furnace cooling experiment that the secondary γ" phase precipitation is related to the working high temperature and cooling way; the TCP phase which contains many W, Re elements appears in the abnormally high temperature region of the trailing edge, and the phase is identified as the μ phase; the microhardness of the leading edge and trailing edge position of different service time decrease significantly, and the decrease of microhardness is positively correlated with the increase of γ" phase size and decline of volume fraction.; therefore, the γ" phase size and volume fraction can be used as the evaluation parameters of the tissue damage of the material.