No abstract

The 22Cr25NiwCoCu austenitic stainless steel was developed by aB Sandvik Material Technology in Sweden. due to its high creep strength and good corrosion resistance, this material is well suited for use in superheaters in advanced coal-fired power boilers as well as in other types of steam boilers using various types of fuel. The examined material was subject to long-term ageing for the time of annealing up to 20 000 h at 700 and 750°C. Precipitation processes and microstructure stability as-received and after ageing were investigated. Examination of the microstructure was conducted using scanning electron microscopy. The identification of secondary phases was carried out by X-ray phase composition.Using the results of the investigations of precipitation processes in the microstructure, both within the grains and at the grain boundaries, their statistical analysis was carried out. To illustrate this impact, the following parameters were used: surface area and equivalent diameter of precipitates. Based on the surface area measurements, the percentage of the phase in the reviewed photo's total area was calculated.

Structure of the S304h Steel after 20,000 hourS of ageing the s304H steel is used in the construction of pressure components of boilers with supercritical operating parameters. the paper presents the results of the research on the microstructure after ageing for 20,000 hours at 650 and 700°C. the microstructure examination was performed using scanning and transmission electron microscopy. the precipitates were identifies using transmission electron microscopy. the influence of ageing time on microstructure changes and the precipitation process of the tested steel is described. the presented research results are an element of material characteristics of the new generation of steel, which are used in the design work of pressure devices of steam boilers and in diagnostic work during operation.