Session: MF-02-05 Materials for Hydrogen Service-High Alloy Materials 2

Paper Number: 121158

121158 - Effect of Temperature on Hydrogen Assisted Fatigue Crack Growth Rate of Austenitic Stainless Steel 

It is well-documented experimentally that the influence of hydrogen on the mechanical properties of structural alloys strongly depends on temperature. A typical curve plotting any hydrogen-affected mechanical property as a function of temperature gives a temperature T_HE,max, where the degradation of this mechanical property reaches a maximum. Above and below this temperature, the degradation is less. The temperature T_HE,max is alloy dependent and, up to now, can only be measured experimentally. Due to its simplicity, T_HE,max is typically measured by tensile testing and for austenitic stainless steels, a T_HE,max of about -70°C is well established. However, an open question is if T_HE,max also depends on the test method. This investigation provides results of a 1.4404 austenitic stainless steel to measure T_HE,max using fatigue crack growth tests. CT25 specimens were precharged at 30 MPa gaseous hydrogen at 350°C resulting in a hydrogen concentration of about 60 wppm. Fatigue crack growth rates of hydrogen charged and unchgarged specimens at ΔK = 20-30 MPa*m^0,5 were measured in a temperature range between -100 and +100°C to identify T_HE,max. The results will be compared to tensile test results from similar steels published previously in the open literature.

Presenting Author: Thorsten Michler Fraunhofer IWM

Presenting Author Biography: Working on hydrogen efects in structural alloys for more than 20 years.
Currently group manager for "lifetime concepts for hydrogen applications" at Fraunhofer IWM.

Authors:

Thorsten Michler Fraunhofer IWM
Igor Varfolomeev Fraunhofer Institute for Mechanics of Materials IWM