Influence of Temperature and Long Term Ageing on the Fatigue Crack Growth in a Precipitation Hardened Martensitic Stainless Steel

The high-temperature Fatigue Crack Growth (FCG) behaviour of a 15-5 PH (precipitation-hardened) martensitic stainless steel was investigated in three different metallurgical conditions, i.e., as-received, aged at 300 °C for 1000 h and 5000 h. FCG tests were conducted at room temperature and 300 °C under constant amplitude loading with two load ratios (R = 0.1 and 0.7) and under variable amplitude loading. The results indicate that the fatigue crack growth rates (FCGRs) increase with R-ratio at the lower ΔK regime and merge together in the high ΔK regime, regardless of ageing conditions and temperature. At 300 °C, the FCGRs are higher than at room temperature for all ageing conditions. Under variable amplitude loading, the same retardation effect was observed for all the given ageing conditions at room temperature