Isolation Ring 소재의 역설계로 개발된 원심주조 내열합금소재의 기계적 특성 평가

Abstract

This paper is a study on the evaluation of the mechanical properties of centrifugal casting heat-resistant alloy materials developed by inverse design of isolation ring material used in the turbine parts of gas turbine for power generation. For this paper, mechanical properties were identified using component analyzer by spark atomic emission spectrometry and universal testing machine, Charpy V-Notch impact tester, hardness tester, and further microstructure and macrostructure test, copper sulfate-sulfuric acid test were performed to check the integrity of the material. The material is a high Cr-Ni material (SCS13A), manufactured by centrifugal casting method according to TAKASAGO Specification of Mitsubishi Hitachi Power Systems, LTD. such as SGC-0133, SGC-0048. ASTM Code has been selected for identification of material properties with the material's inner surface, outer surface, mean-radius positions. According to the test results, the hardness was higher in order of inner surface > outer surface > mean-radius positions. At room temperature, the tensile strength was higher in order of mean-radius positions > inner surface > outer surface and the yield strength was higher in order of inner surface > mean-radius positions > outer surface, the elongation rate was higher in order of outer surface > mean-radius positions > inner surface. Also, at elevated(600°C) temperature, the tensile strength was higher in order of outer surface > inner surface > mean-radius positions, and the yield strength was higher in order of inner surface > outer surface > mean-radius positions, the elongation rate was high in order of outer surface > mean-radius positions > inner surface. The ferrite volume was 12.5% at axial position and 10.6% at radial position, and there were no defects or publications that could have a significant effect on the material as a result of the macrostructure test. In addition, as a result of the sensitization corrosion by the copper sulfate-sulfuric acid test, confirmed that there was no possibility of a crack caused by the occurrence of standing corrosion and the corrosion of standing stress.

However, in order to stabilize the quality at elevated temperature of the centrifugal casting material(SCS13A), it seems necessary to adjust the elements of alloys such as Ni or N, Mn.