Effects of Precipitates Evolution on Low Stress Creep Properties in P92 Heat-resistant Steel

The evolution of precipitates in P92 heat-resistant steel sustained under thermal aging at 923 K for different times were analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), while the effects of precipitates evolution on the low stress creep properties were experimentally analyzed through uniaxial creep testing and multiaxial “helicoid spring creep testing”. The results demonstrate that the coarsening of M 23 C 6 carbide is significantly slower than the Laves phase in the thermal aging of 0~8000 h. The creep resistance of the P92 heat-resistant steel is enhanced at 923 K aging for 3000 h, and the strengthening effect is significantly apparent under the lower stresses. Moreover, the microstructure degradation factor of the P92 heat-resistant steel in the low stress region at 923 K is different that under the lower stresses of 20 MPa and 35 MPa is mainly Laves phase and the higher stresses of 65 MPa and 75 MPa is mainly M 23 C 6 carbide.