Creep crack growth of HK40 steel: Microstructural effects

Creep crack growth tests at 871 °C have been performed on compact tension specimens of HK40 steel having different microstructures. The skeleton-shaped carbides on the grain boundaries have a higher resistance to crack growth than the blocky-shaped carbides. The secondary carbide size and distribution explicitly affect crack growth behavior. There exists a critical size of the secondary carbides. With an increase in the secondary carbide size, the resistance to crack growth increases up to the critical size and decreases beyond the critical size.