Crack growth behaviour in austenitic and ferritic steels during thermal quenching from 550°C

In this investigation small, cylindrical specimens of 316, 9CrlMo and 12CrMoV steels and alloy 718 were subjected to a ‘ranking test’ whereby some 30 000 thermal quench cycles were imposed and ultimate crack penetration determined metallographically. Further tests on large specimens of 316 and 1/2CrMoV steels are reported where fewer cycles were involved. Crack progress was also assessed from striation measurements which furnished evidence ofacceleration away from a notch and ofsubsequent arrest. It is concluded that under the conditions oftesting, 316 steel shows the least resistance to crack penetration, the ferritic steels demonstrate intermediate behaviour while alloy 718 is most resistant to crack initiation.