Experimental and constitutive modeling investigation of high-temperature creep behavior and life prediction of PCrNi3Mo steel

PCrNi 3 Mo steel is widely used in key parts of gun system, such as gun barrel and gun tail, which are subjected to harsh thermo-mechanical environment. This study systematically investigates the creep behavior and microstructural evolution of PCrNi 3 Mo steel at 600 °C under 210-300 MPa. The stress exponent n was determined to be 4.65, which indicated that the steel showed typical dislocation creep mechanism at 600 °C. In the fracture observation, there are dimples under all stress conditions, which indicates that the creep failure is dominated by ductile fracture. With the increase of stress, the densities of both high-angle and low-angle grain boundaries increased, and the martensite lath structure began to become wider. At 300 MPa, the enhanced {111}//loading direction and <101>//loading direction textures provide favorable crystallographic conditions for the activation of the {110}<111> slip system, which promotes dislocation slip and climb during high-stress creep. Moreover, compared with 210 MPa, the Zener pinning strength is increased by about 53% at 300MPa, which is beneficial to inhibit boundary migration and lath coarsening. Based on the Monkman-Grant (MG) relation, a creep life prediction model considering precipitate coarsening was established. Furthermore, a constitutive model based on the Continuum Damage Mechanics framework was employed to describe the creep deformation of the steel, and the calculated curves agreed well with the experimental results.