热腐蚀对GH37高温合金蠕变强度的影响

采用在GH37合金上涂敷NaCl(25Wt％)及Na_2SO_4(75Wt％)的方法,研究了700℃及850℃下热腐蚀对蠕变强度的影响。发现试样涂上混合盐后,蠕变第二阶段速率增大,并严重降低二个温度下的蠕变断裂寿命及断裂塑性。值得提出的是,尽管700℃下合金几乎不经受热腐蚀,但与850℃的相比,对蠕变强度的影响却是700℃时更为强烈。 由断口观察推测,涂盐试样在700℃下蠕变寿命下降是由于缩短了蠕变裂纹萌生期。850℃下蠕变寿命的下降是由于蠕变裂纹扩展速率的增大。 试样上渗涂Al-Cr涂层后,可以大大提高在热腐蚀介质中合金的蠕变强度。

INFLUENCE OF HOT CORROSION ON THE CREEP STRENGTH OF THE SUPERALLOY GH 37

The effect of hot corrosion on creep strength of the superalloy GH37 at 700℃ and 850℃ has been studied by comparing the results for both bare specimens and specimens coated with a salt mixture of 25％ NaCl and 75％ Na_2SO_4. Results show that the secondary creep rate increases and that the life of creep rupture and ductility decreases considerably with salt coated specimens. The effect of hot corrosion on creep strength of alloy at 700℃ is much more severe than that at 850℃, although the alloy is nearly unattacked at 700℃ by salt. Direct observation of fracture surface leads us to suggest that for the salt coated specimens the decrease of creep rupture life at 700℃ is due to the reduction, of the crack initiation time, while the reduction of the creep rupture life at 850℃ is due to the acceleration of creep crack growth rate. The creep strength of the alloy can be improved by means of Al-Cr diffusion coating on the specimen.