Microstructure and Mechanical Properties of Modern 11%Cr Heat-Resistant Steel Weld Joints

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.

Analysis of Mechanical Properties of Welded Joint Metal from TPP Steam Piping after Its Operational Degradation and Hydrogenation

“…The premature failure of welded joints is a serious problem in thermal power engineering because the creep resistance of weld metals decreases faster than that of base metals due to high temperatures and applied stresses [3][4][5]. Areas of welds are potentially dangerous because they are more structurally heterogeneous than the surrounding metal and are zones of localization of stresses and deformations [6][7][8].…”

Microstructure and Properties of Dissimilar Joints of AISI 430 Steel with Inconel 625 Obtained by Electron Beam Welding

“…Welding is one method to join these materials [14]. However, very serious metallurgical and technological problems may arise during welding, which primarily stems from differences in the physicochemical properties of materials, such as the melting point, thermal conductivity or expansion coefficients, or the weld material structure.…”