| 英文摘要 |
This study the cause of damage to the 800H circulation fan side plate. The test methods of appearance observation, composition analysis, sensitization test, material metallography and fracture surface analysis were included. The results were shown the 800H side-plate failure by uneven matter. The material composition of the side plate met the 800H specification; oxalic acid test shown that the side plate had sensitization problems and the material strength was reduced; 800H should be the metallographic structure of the Austenite, but the upper and lower surfaces of the cracks on both sides of the side plate shown columns Crystals, the middle was Austenite; the difference of Ni content between the middle and the upper and lower surfaces were more than 10%, this area was not the original 800H. That concluded which side plate was locally heated to a high temperature of 800H melting point temperature, the liquid alloy cooled by heat transfer and the columnar crystal grew on the surface; the temperature at the center of the thickness dropped slowly to form equiaxed Austenite, meanwhile the Ni migrates to the heated area. The surface of fractured was clearly divided into the rugged area on both sides and the middle flat area, which corresponded exactly to the metallographic structure of the sandwich phenomenon shown in the cross-section metallography. The fracture started from the small gap at the outer edge of the side plate, which hit the columnar crystals on both the upper and lower surfaces, cracks quickly in the coarse columnar regions and torn through the side plates.. |
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