Thermomechanical fatigue crack growth in a cast polycrystalline superalloy
2014 (English)In: EUROSUPERALLOYS 2014 - 2ND EUROPEAN SYMPOSIUM ON SUPERALLOYS AND THEIR APPLICATIONS, EDP Sciences , 2014, Vol. 14, no 19004Conference paper (Refereed)
Thermomechanical fatigue (TMF) crack growth testing has been performed on the polycrystalline superalloy IN792. All tests were conducted in mechanical strain control in the temperature range between 100 and 750 degrees C. The influence of in-phase (IP) and out-of-phase (OP) TMF cycles was investigated as well as the influence of applying extended dwell times (up to 6 hours) at the maximum temperature. The crack growth rates were also evaluated based on linear elastic fracture mechanics and described as a function of the stress intensity factor K-I. Without dwell time at the maximum temperature, the crack growth rates are generally higher for the OP-TMF cycle compared to the IP-TMF cycle, when equivalent nominal strain ranges are compared. However, due to the fact that the tests were conducted in mechanical strain control, the stress response is very different for the IP and OP cycles. Also the crack closure level differs significantly between the cycle types. By taking the stress response into account and comparing the crack growth rates for equivalent effective stress intensity factor rages Delta K-eff defined as K-max - K-closure, very similar crack growth rates were actually noticed independent of whether an IP or OP cycle were used. While the introduction of a 6 hour dwell time significantly increased the crack growth rates for the IP-TMF cycle, a decrease in crack growth rates versus Delta K-eff were actually seen for the OP-TMF cycle. The fracture behaviour during the different test conditions has been investigated using scanning electron microscopy.
Place, publisher, year, edition, pages
EDP Sciences , 2014. Vol. 14, no 19004
, MATEC Web of Conferences, ISSN 2261-236X ; 14
IdentifiersURN: urn:nbn:se:liu:diva-117399DOI: 10.1051/matecconf/20141419004ISI: 000351930400074OAI: oai:DiVA.org:liu-117399DiVA: diva2:807743
2nd European Symposium on Superalloys and their Applications