The purpose of the present study is to evaluate the potential of X20 and P92 steels as materials for applications operating under combined effect of mechanical wear and alternating high/low temperature conditions. Generally, with longer tempering time and higher tempering temperature, the number of carbide precipitates decreased, while their relative spacing increased. Before tempering, the morphology of the steel matrix (grain size, microstructure homogeneity) governed the wear resistance of both steels, while after tempering wear response was determined by the combination of the number and the size of carbide particles. After tempering, in X20 steel larger number of stable M23C6 carbides was observed as compared with P91 steel, resulting in lower wear rates. It was observed that for both steels, a similar combination of number, density and size distribution of carbide particles provided the highest wear resistance.
COBISS.SI-ID: 1289130
The purpose of this investigation was to identify the distribution of ultrafine particles in a steel matrix introduced through a conventional melting and casting method, and above all to determine the methodology and analysing techniques suitable for the analysis and identification of ultrafine particles incorporated into the steel matrix. In the frame of this work, steels dispersed with Al2O3 ultrafine particles were produced by a conventional casting method and their microstructure investigated with light microscopy (LM), scanning electron microscopy (SEM) and auger electron spectroscopy (AES). Microstructural analyses show that the distribution of the Al2O3 ultrafine particles is non-uniform and has a high degree of agglomeration. Furthermore, for a detailed analysis of the nanoparticles a specific preparation and characterization using advanced microscopic techniques is required.
COBISS.SI-ID: 1213610
In thermal power stations, 9-12 % Cr steels are widely used for components operating at elevated temperatures. In the present work, the influence of quenching and tempering temperatures on microstructure evolution of 9-12 % Cr creep resistant steels was studied. It was found that quenching and tempering parameters influence the number, size, and mutual spacing of precipitates in the steel. The effect of different heat treatment parameters on the steady state creep rate and time to rupture showed that for the higher quenching temperature, the number of precipitates increases while their mutual spacing decreases, which leads to improved creep resistance. Effect of tempering temperatures is not so pronounced as in the case of quenching temperature.
COBISS.SI-ID: 1249450