Plenty of oxidation etching pits are found on the surface of the specimen after the thermal fatigue test, and the surface principal crack is prone to propagate through these etching pits.
实验结果发现，试样表面出现大量的氧化腐蚀坑，表面主裂纹优先通过这些腐蚀坑扩展。
2
By means of chemical composition analysis, mechanical property test and microstructure examination, the results showed that this defect was result of rough surface and not the crack existed in matrix.
The treatment technology of "chrome-automatic painting" on the surface of the corroded specimens will make crack more clear to be observed and recorded in the test.