Hot corrosion cracking of Nimonic 80A

Experimental investigations have been carried out to study the hot corrosion crack growth behaviour ofN imonic BOA in a combustion gas containing sulphur, vanadium or sodium at 600 and 700°C. The time to rupture has been found to be inversely proportional to the applied stress, and the crack growth rate, da/dt, can be described by the LEFMparameter K, the stress intensity factor. The threshold stress intensity factor, K_th , and the critical stress intensity factor, K_c, have been found to be functions oftemperature and corrodent level. In the case ofsulphur, K_th decreases continuously with increasing sulphur content in the fuel. In the case of vanadium or sodium, there appears to be a critical level ofcorrodent for the worst attack.