CReep ResIstanCe of VM12 steelThis article presents selected material characteristics of VM12 steel used for elements of boilers with super-and ultracritical steam parameters. In particular, abridged and long-term creep tests with and without elongation measurement during testing and investigations of microstructural changes due to long-term impact of temperature and stress were carried out. The practical aspect of the use of creep test results in forecasting the durability of materials operating under creep conditions was presented. The characteristics of steels with regard to creep tests developed in this paper are used in assessment of changes in functional properties of the material of elements operating under creep conditions.

This paper presents selected material characteristics of Super 304H austenitic steel used for elements of boilers with super- and ultra-critical steam parameters. In particular, abridged and long-term creep tests with and without elongation measurement during testing and investigations of microstructural changes due to long-term impact of temperature and stress were carried out. The practical aspect of the use of creep test and structure investigation results in forecasting the durability of materials operating under creep conditions was presented. The characteristics of steels with regard to creep tests and structure investigations developed in this paper are used for estimation of changes in functional properties of the material of elements operating under creep conditions.

This article presents the results of investigations on HR6W alloy and Sanicro 25 steel and the dissimilar welded joint made of them. The characteristic images of microstructure of the investigated materials in the as-received condition and following the creep test, observed with a scanning electron microscope (SEM), are shown. The X-ray analysis of phase composition of the existing precipitates was carried out. The method for evaluation of creep strength based on abridged creep tests carried out at a temperature higher than the design one is presented. The obtained results do not deviate from the values of creep strength determined in longterm creep tests. The maximum difference in creep strength of the investigated materials is ±20%, which is in compliance with the acceptable scatter band. The methodology presented can be used for verification of creep strength (life time) of the material of finished components to be operated under creep conditions.

This paper presents the characteristics of the performance of austenitic steel Super 304H and HR3C used for construction of boilers with supercritical and ultra-supercritical steam parameters. Characteristic microstructure images of the examined steels in the as received condition observed with the scanning electron microscope are shown. The method for strength assessment based on abridged creep tests carried out at a temperature higher than the design one is presented on the example of examined steels. It has been demonstrated that the obtained results do not deviate from the values of creep strength determined in long-term creep tests. The maximum difference is ± 20%, which is in compliance with the acceptable scatter band. The presented methodology can be used for verification of creep strength.

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