高温疲労破面のX線フラクトグラフィ

抄録

An X-ray fractographic study was made on the fatigue fracture surface of HT80 and S53C steels at elevated temperatures up to 400°C.
Emphasis was put on examing the effects of oxide film and fracture surface roughness on the residual stress and half-value breadth of fracture surface at elevated temperatures. It was found that the oxide film induced on the fracture surface at elevated temperatures was thin enough and was not detrimental for the application of X-ray fractography to analyze the fracture surface of steels up to 400°C.
However, it was also found that the increased fracture roughness beyond a certain value was detrimental. The value was estimated as about 7.5μm in the center line average roughness. For this case, it is difficult to apply X-ray fractography because both the residual stress and half-value breadth are controlled not only by K_max or ΔK but also by the roughness of fracture surface.