Creep-fatigue behaviour of CoCr22Ni22W14 in the temperature range 850 °C < T < 1200 °C

The creep-fatigue behaviour of CoCr22Ni22W14 was investigated by varying the frequency, the total strain rate and the temperature. With decreasing frequency and increasing temperature, the cyclic deformation behaviour is more and more influenced by creep processes. The recorded hysteresis loops for low frequencies at 1000 and 1200 °C show that the plastic deformation takes place under nearly constant tensile and compression stresses. Compared with fatigue tests at higher frequencies, the dislocation arrangement after failure is altered, and well developed subgrain walls appear. For low frequencies the stress dependence of the plastic strain rates determined during the fatigue tests at half of the lifetime corresponded very well to the stress dependence of the stationary creep rates from creep tests. The fatigue data presented can be correlated very well with the frequency-modified Manson-Coffin relationship and with the frequency-modified Basquin relationship.