Effect of hydrogen on tensile properties and fracture behavior of PH 13-8 Mo steel

The tensile properties and fracture behavior of PH 13-8 Mo steel after subjected to pre-charged hydrogen were investigated by slow strain rate tensile tests. The results suggest that hydrogen slightly increases yield strength, while decreases tensile strength. The susceptibility to hydrogen embrittlement of specimens aged at 650 degrees C firstly reduces and then increases as the aging time increases, reaching the lowest value at aging time 4 h. This is dominantly attributed to the highest content of austenite. Moreover, hydrogen-induced crack nucleation sites initiate from lath, packet and prior austenite grain boundaries. Crack propagation passes through lath boundaries and walks along packet, prior austenite grain boundaries. Scanning electron microscopy result indicates that hydrogen-charged specimens show quasi-cleavage fracture and intergranular fracture in annular brittle zone while dimple fracture is observed in hydrogen-free specimens. (C) 2016 Elsevier Ltd. All rights reserved.