Cyclic deformation characteristics and fatigue crack growth behaviour of a newly developed aerospace superalloy Haynes 282

Abstract

Strain-controlled low cycle fatigue (LCF) and fatigue crack growth (FCG) tests were performed on a newly developed Aerospace superalloy, Haynes 282, in its standard heat treatment condition which consists of a solution heat treatment of 1130°C/2h/water-quench followed by ageing at 1010°C/2h/air-cool and 788°C/8h/air-cool. Cyclic deformation characteristics of the Haynes 282 at room temperature (25°C) were obtained from the LCF test. The LCF test results showed that Haynes 282 experienced a relatively short period of initial cyclic hardening followed by a regime of cyclic softening to specimen failure at all the strain amplitudes employed in the work. Additionally, cyclic deformation parameters determined in the work indicate strong fatigue deformation resistance of the newly developed superalloy. On the other hand, room temperature FCG test results showed that an increase in the stress ratio leads to a rise in the crack growth rate. However, in contrast to common assumption, the loading frequency was observed to have an effect on the crack growth behaviour at room temperature. Furthermore, an increase in temperature from 25°C to 600°C at a testing frequency of 15Hz resulted in an increase in the fatigue crack growth at all stress intensities. However, at a frequency of 0.05Hz, over a relatively large stress intensity range (ΔK), the fatigue crack growth rate decreased with an increase in temperature. The effect of temperature on the fatigue crack growth rate of Haynes 282 are discussed in terms of homogeneity of slip, roughness induced crack closure and dynamic strain ageing.