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本文研究了镍基形变高温合金GH37涂10％NaCl+90％Na_2SO_4混合盐后的蠕变断裂行为,并与空气环境进行了比较.试验结果表明,在700—850℃,196—510MPa试验条件下,涂盐使合金的蠕变寿命和塑性大幅度降低,但最小蠕变速率几乎不受影响;涂盐试样的蠕变激活能和应力敏感指数都与空气中相当,这说明热腐蚀并不改变合金的蠕变机制;在温度较高、应力较低(800℃、265MPa)时,晶粒越细则涂盐试样的蠕变寿命下降越严重;但在温度较低、应力很高(700℃、510MPa)时,晶粒尺寸适中的涂盐试样蠕变寿命最长.涂盐环境下蠕变寿命的降低是由于合金晶界受到贫Cr和硫化损害所致,贫Cr引起晶界上碳化物分解而降低晶界抗剪切强度.贫Cr和硫化导致晶界裂纹易于萌生并加速其扩展.
In this paper, the creep rupture behavior of Ni-based superalloy GH37 coated with 10% NaCl + 90% Na 2 SO 4 mixed salt was studied and compared with the air environment.The results show that under the experimental conditions of 700-850 ℃ and 196-510MPa , Coated with salt greatly reduces the creep life and ductility of the alloy, but the minimum creep rate is almost unaffected; the creep activation energy and stress sensitivity index of salt-coated samples are comparable with that of air, which indicates that hot corrosion is not (700 ℃, 265MPa). The thinner the grain, the more serious the decline of creep life of salt-coated specimens. However, at lower temperature and high stress (700 ℃, 510MPa), the creep life of salt coated samples with moderate grain size is the longest.The reduction of creep life under salt coated environment is due to the Cr-depletion and sulfide damage of alloy grain boundaries, Decomposition of carbides reduces the shear strength at grain boundaries, and Cr-depletion and sulfidation lead to easy initiation of grain boundary cracks and accelerated expansion.