Study on the Mechanism of Oxidation-Accelerated Creep Damage of P92 Steel in 650 °C Superheated Steam

Abstract

In this study, creep tests were conducted on P92 steel at 650 °C under 110–155 MPa in both air and superheated steam environments to investigate the interaction between creep and oxidation. The combined effects of steam and different applied stresses influenced the structure and compactness of the oxide film, as well as the mechanisms of creep damage and creep crack growth, ultimately affecting creep rupture behavior. High applied stress levels (≥ 130 MPa), due to minimal oxidation and a rapid creep rate, the steam environment has a limited impact on creep life and material toughness. Additionally, crack propagation was hindered by the intact martensitic lath, delaying the creep fracture. In contrast, under low applied stress (≤ 110 MPa) in steam, cracking of grain boundary oxides facilitated creep crack growth along high-angle grain boundaries of recrystallization grains, which formed due to severe deformation during necking process in accelerated creep stage. Simultaneously, the presence of oxide on grain boundaries promoted grain boundaries sliding at the crack tip, thereby accelerate the accumulation of creep damage and reducing the toughness of the material.