Abstract
The secondary creep rate and rupture life of the nickel-base superalloy GH37 were determined at 700 and 850 °C under stresses of 471 and 196 MN m −2, and the influence of the hot corrosion due to a 75wt.%Na 2SO 4-25wt.%NaCl coating on the creep strength of the alloy was evaluated. It was found that the secondary creep rate increased and the creep rupture life and ductility decreased considerably for the alloy coated with the Na 2SO 4NaCl mixture. The influence of hot corrosion due to the Na 2SO 4NaCl coating on the creep strength of GH37 was more severe at 700 °C than at 850 °C. Observation of the fracture surface, together with the results of creep rupture tests, leads us to suggest that the decrease in the creep rupture life of the Na 2SO 4NaCl-coated specimens at 700 °C is due to a reduction in the incubation period of the crack initiation but that the decrease in the creep rupture life at 850 °C is due to an increase in the creep crack propagation rate. A chromoaluminide coating on the specimen surface can increase significantly the creep strength of the alloy under hot corrosion.
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