Creep crack growth properties of P91 and P22 welded joints

Abstract

The ferritic P22 and bainitic-martenstic P91 steel welded joints operating at elevated temperatures are highly vulnerable to premature failure, because microstructure gradients can lead to cracking in the heat-affected zone, commonly referred to as type IV cracking. Creep crack growth tests have been performed using compact tension specimens made of P91 and P22 weld joints at temperatures of 600 and 550 degrees C, respectively. The creep crack growth characterization through empirical equation of C* was the main fracture parameter for relating behaviour of component's regions. Results have shown that, for a specific value of C* parameter, the weld metal and heat-affected zone had similar crack growth rates, which were about two times faster than base metal rates, because of lower creep strength that leads to a conclusion that the creep cracks will most likely initiate in the heat-affected zone region.