Relationship between Hydrogen-induced Additive Stress and Threshold Cracking Stress for a High-strength Steel

The relationship between hydrogen induced additive stress and threshold cracking stress of high strength steel 40CrMoTi was studied using SSRT.The hydrogen-induced additive stress,σad,increased linearly with the increase of both yield strength and logarithm of hydrogen concentration for the samples,i.e,σad=-260+0.226σys+63.9 lnC0.The threshold stress decreased with the increase of logarithm of hydrogen concentration for the samples,i.e,σHIC=863-145 lnC0(σs=900 MPa),σHIC=891-183 lnC0(σs=1 050 MPa).The relative fracture stress σF(H)/σF during charging with hydrogen decreased with the increase of logarithm of hydrogen concentration for the samples,i.e,σF(H)/σF=0.97-0.18 lnC0(σs=900 MPa),σF(H)/σF=0.95-0.24 lnC0(σs=1 050 MPa).