Abstract
In addition to good high-temperature creep resistance and adequate heat resistance, steels for the power industry must have, among other things, good weldability. Weldability of such steels is one of the criteria determining whether or not the material is suitable for applications in the power industry. Therefore, when materials such as martensitic steel Thor 115 (T115) are introduced into the modern power industry, the quality and properties of welded joints must be assessed. The paper presents the results of metallographic and mechanical investigations of T115 martensitic steel welded joints. The analysis was carried out on joints welded with two filler metals: WCrMo91 (No. 1) and EPRI P87 (No. 2). The scope of the investigations included: microstructural investigations carried out using optical, scanning and transmission electron microscopy and mechanical testing, i.e., Vickers microhardness and hardness measurement, static tensile test and impact test. The macro- and microstructural investigations revealed correct structure of the weld, without welding imperfections. The microstructural investigations of joint No. 1 revealed a typical structure of this type of joint, i.e., the martensitic structure with numerous precipitates, while in joint No. 2, the so-called Nernst’s layers and δ-ferrite patches were observed in the weld fusion zone as well as the heat affected zone (HAZ). The mechanical properties of the test joints met the requirements for the base material. A slight influence of the δ-ferrite patch on the strength properties of joint No. 2 was observed, and its negative effect on the impact energy of HAZ was visible.
Highlights
The construction of modern supercritical or ultra-supercritical boilers to reduce air emissions and fuel consumption required the use of modern creep-resistant materials, including but not limited to 9–12% Cr martensitic steels, for boiler pressure components.Martensitic steels are intended for, but not limited to, steam superheater components which are considered essential for a power unit [1,2]
Thor 115 (T115) steel had a structure of tempered martensite with numerous particles packetsatand lathes in thegrain blocks were variable
T115 steel joints welded with two filler metals: CrMo91 (No 1) and EPRI P87 (No 2)
Summary
The construction of modern supercritical or ultra-supercritical boilers to reduce air emissions and fuel consumption required the use of modern creep-resistant materials, including but not limited to 9–12% Cr martensitic steels, for boiler pressure components.Martensitic steels are intended for, but not limited to, steam superheater components which are considered essential for a power unit [1,2]. The construction of modern supercritical or ultra-supercritical boilers to reduce air emissions and fuel consumption required the use of modern creep-resistant materials, including but not limited to 9–12% Cr martensitic steels, for boiler pressure components. The limited operating temperature of martensitic steels resulted in the introduction of austenitic steels in the power industry [2,3,4]. Due to their adverse physical properties and susceptibility to intergranular and stress corrosion, the creep-resistant austenitic steels give rise to a number of operational problems [5,6]. Research aimed at the development of new types of steel with ferritic matrix capable of operating at above 610 (620) ◦ C is being carried out in numerous research centres
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