Assessment of microstructure stability and mechanical properties of X10CrWMoVNb9-2 (P92) steel after long-term thermal ageing for high-temperature applications

Abstract

This paper presents changes in mechanical properties and microstructure of the material of components of a power station boiler made of X10CrWMoVNb9-2 (P92) steel after long--term thermal ageing. Mechanical properties and microstructure were examined on material in initial heat treatment condition and after long-term thermal ageing up to 100,000 h at 600 and 650• C. The microstructure was observed using a scanning and transmission electron microscope. The examinations of steel microstructure and mechanical properties in initial heat treatment condition have confirmed that the requirements for this steel are met. Longterm thermal ageing at a temperature similar to the operating one as well as mechanical properties and microstructure examinations allowed to assess the effect of long-term impact of temperature on the properties and microstructure of P92 steel. The presented method can be used for evaluation and qualification of microstructural changes in power station boiler components operating under creep conditions. K e y w o r d s : P92 steel, microstructure, mechanical properties, long-term thermal ageing

Hydrogen pre-charging effects on the notch tensile properties and fracture behaviour of heat-affected zones of thermally aged welds between T24 and T92 creep-resistant steels

“…The most significant microstructural change in Grade 92 steels during their long-term ageing and/or creep exposure is the additional precipitation of intermetallic Fe 2 (W, Mo) based Laves phase, typically in the vicinity of M 23 C 6 carbides [19][20][21][22][23][24].…”

The effect of temperature on the changes of precipitates in low-alloy steel

“…19,23,24 The basic statistical measurements describing the structure of the data set, calculated by the Gaussian probability distribution assumption, are presented in Table 2. Results in the form of distributions of equivalent diameters of the occurring precipitates for the analysed conditions of the tested low-alloy steel are shown in Fig.…”

Ageing Effects on Microstructure, Mechanical Properties, and Fracture Behaviour of 9Cr-1.5Mo-1Co-VNbBN Martensitic Steel Welded Joint for High Temperature Application

“…These intermetallic precipitates show clear bright appearance in the SEM visualization using backscattered electrons contrast (Figures 3(b), 3(d), 4(b), and 4(d)) due to their notable molybdenum content and thus much higher average atomic number compared to other precipitated phases in the microstructures. The precipitation of Laves phase belongs to the most significant microstructural changes in 9Cr creep-resistant steel during its long-term thermal or creep exposure [13][14][15]. Furthermore, as indicated in present study by both the experimental measurements and thermodynamic calculations ( Table 2), beside the Laves phase also some other newly precipitated phases, namely, the Cr(V,Nb)N type Z-phase and Nb-rich MC carbides, have been revealed in thermally exposed state at 625 ∘ C for 30 kh hours.…”