THE INFLUENCE OF TEST TEMPERATURE ON IMPACT FATIGUE CRACK GROWTH BEHAVIOR IN QUENCHED AND TEMPERED Cr‐Mo ALLOY STEELS WITH DIFFERENT PRIOR AUSTENITE GRAIN SIZES

TLDR: In this paper, the influence of prior austenite grain size, ductile-brittle transition temperature and test temperature on impact fatigue crack growth rate was investigated by means of fracture mechanics and fractography in quenched and tempered Cr-Mo alloy steel.

Abstract: — Impact fatigue tests were carried out using a rotating-disk type impact fatigue testing machine The influence of prior austenite grain size, ductile-brittle transition temperature and test temperature on impact fatigue crack growth rate was investigated by means of fracture mechanics and fractography in quenched and tempered Cr-Mo alloy steel in which the prior austenite grain size was varied from 8–3 to 25-4 μm The results in impact fatigue tests were compared to those under non-impact conditions The crack growth rates associated with striation formation were insensitive to the change in prior austenite grain size, ductile-brittle transition temperature and test temperature regardless of impact and non-impact fatigue When the material was in the brittle condition, impact fatigue gave rise to a transition from striation formation to intergranular and cleavage cracking Such a transition will result in the acceleration of crack growth rate The Paris Law exponent values in impact fatigue were reasonably expressed by the ratio of test temperature to ductile-brittle transition temperature