Five Co-modified P92-type steels with different contents of Cr, W, Mo, B, N, and Re have been examined to evaluate the effect of the chemical composition on the evolution of Laves phase during creep at 650 °C. The creep tests have been carried out at 650 °C under various applied initial stresses ranging from 80 to 200 MPa until rupture. An increase in the B and Cr contents leads to a decrease in the size and volume fraction of M₂₃C₆ carbides precipitated during tempering and an increase in their number particle density along the boundaries. In turns, this affects the amount of the nucleation sites for Laves phase during creep. The (W+Mo) content determines the diffusion growth and coarsening of Laves phase during creep. Susceptibility of Laves phase to coarsening with a high rate is caused by the large difference in Gibbs energy between fine and large particles located at the low-angle and high-angle boundaries, respectively, and can cause the creep strength breakdown. The addition of Re to the 10%Cr steel with low N and high B contents provides the slowest coarsening of Laves phase among the steels studied.

In metastable austenitic stainless steels the formation of high dislocation densities, compressive residual stress states, strain-induced martensite and nanocrystalline regions are the most important consequences of mechanical surface treatments leading to retarded fatigue crack initiation as well as propagation. These properties can be altered in a characteristic way applying different deep rolling temperatures. The main objective of this paper is to clarify the role of the different near surface microstructures introduced by deep rolling operations on the fatigue behaviour of steel AISI 304 especially in the low cycle fatigue region. For this purpose special experimental techniques were applied allowing deep rolling operations in the temperature range between −192 °C and +700 °C. Results clearly show that the amount of strain induced martensite by deep rolling in near surface layers is less important than the stability of the microstructures under fatigue loading.

This paper presents the results of an experimental investigation of a 12% Cr steel where a significant increase in Charpy impact toughness and a slight decrease in ductile-brittle transition temperature (DBTT) from 70 °C to 65 °C were obtained through thermo-mechanical processing, including interim hot forging at 1050 °C with long-term annealing at 1000 °C, as compared with conventional heat treatment. At lower temperatures ranging from −20 °C to 25 °C, the value of impact toughness comprised ~40 J cm⁻² in the present 12% Cr steel subjected to thermo-mechanical processing. The amount of δ-ferrite decreased to 3.8%, whereas the size of prior austenite grains did not change and comprised about 40–50 μm. The boundaries between δ-ferrite and martensitic laths were decorated by continuous chains of Cr- and W-rich carbides. M₂₃C₆ carbides also precipitated along the boundaries of prior austenite grains, packets, blocks and martensitic laths. Thermo-mechanical processing increased the mean size of M₂₃C₆ carbides and decreased their number particle densities along the lath boundaries. Moreover, the precipitation of a high number of non-equilibrium V-rich MX particles was induced by hot forging and long-term normalizing at 1000 °C for 24 h.