Mechanical properties of creep enhanced ferritic (CSEF) steels is affected by various parameters, the solutionizing temperature is one of them. The present work demonstrates the effect of solutionizing temperature on microstructure and mechanical properties of CSEF P91 steel. Optical metallography (OM) and Scanning electron microscopy (SEM) were carried out to study the microstructure of P91 steel in different heat treatment conditions. In order to determine the precipitates present in microstructure; X-ray analysis was performed. Moreover, the influence of solutionizing temperature on the mechanical properties (strength, hardness and impact toughness) has also been studied.

Effect of normalizing temperature on microstructural stability and mechanical properties of creep strength enhanced ferritic P91 steel

This paper critically assesses phase transformations occurring after welding and subsequent post weld heat treatments in simulated sub-heat affected zones (HAZ) of P91B steel. Samples for weld-HAZ simulation were produced corresponding to grain-coarsened HAZ, grain-refined HAZ and inter-critical HAZ. Analyses revealed diverse phase transformation mechanisms (for GCHAZ = pipe-diffusion and for GR/ICHAZ = GB-diffusion) owing to manipulation in grain size and boron-enriched nanosized particles as regards virgin steel after welding. However, after PWHT, same phase transformation mechanism (interface diffusion) in all simulated sub-HAZs is observed. Hardness evaluations and prior austenite grain boundaries dissolution confirm GB embrittlement after welding. Boron segregation, the presence of borides and boron-enriched particles heads to ~ 50% drop in hardness deviations enhancing GB hardening after PWHT. Particle refinement is observed after PWHT which is further validated by numerical modelling. In addition, particle evolution during cooling from peak temperature of weld thermal cycle and isothermal holding of PWHT is analysed. Apparent activation energy of nucleation/growth follows descending order, i.e. GC/GR/ICHAZ for nanosized particles during welding.

Phase transformations and numerical modelling in simulated HAZ of nanostructured P91B steel for high temperature applications

Modified 9Cr-1Mo steel finds increasing application in power plant construction because of its excellent high-temperature properties While it has been shown to be weldable and resistant to all types of cracking in the weld metal and heat-affected zone (HAZ), the achievement of optimum weld metal properties has often caused concern The design of appropriate welding consumables is important in this regard In the present work, plates of modified 9Cr-1Mo steel were welded with three different filler materials: standard 9Cr-1Mo steel, modified 9Cr-1Mo, and nickel-base alloy Inconel 182 Post-weld heat treatment (PWHT) was carried out at 730 and 760 °C for periods of 2 and 6 h The joints were characterized in detail by metallography Hardness, tensile properties, and Charpy toughness were evaluated Among the three filler materials used, although Inconel 182 resulted in high weld metal toughness, the strength properties were too low Between modified and standard 9Cr-1Mo, the former led to superior hardness and strength in all conditions However, with modified 9Cr-1Mo, fusion zone toughness was low and an acceptable value could be obtained only after PWHT for 6 h at 760 °C The relatively poor toughness was correlated to the occurrence of local regions of untransformed ferrite in the microstructure

Microstructure and Mechanical Properties of Weld Fusion Zones in Modified 9Cr-1Mo Steel

High temperature creep flow and damage properties of 9Cr1MoNbV steels: Base metal and weldment

A study on influence of shielding gas composition on toughness of flux-cored arc weld of modified 9Cr–1Mo (P91) steel

(1996). Weldability of 9Cr‐1Mo‐Nb, V P91 steel intended for service in the power industry. Welding International: Vol. 10, No. 5, pp. 370-380.

Weldability of 9Cr‐1Mo‐Nb, V P91 steel intended for service in the power industry

An investigation into the properties of the heat affected zone simulated in 9Cr‐1 Mo‐Nb, V(P91) steel intended for service at elevated temperatures

(2000). The weldability of thermomechanically rolled S460ML steel. Welding International: Vol. 14, No. 8, pp. 593-605.

The weldability of thermomechanically rolled S460ML steel

(1998). Welding of P91 steel to other grades of steel for elevated temperature service. Welding International: Vol. 12, No. 7, pp. 509-518.

Welding of P91 steel to other grades of steel for elevated temperature service

We present the issues connected with the manufacture of waterwalls made of modern 7CrMoVTiB10-10 (T24) steel by submerged and TIG welding methods. We give the results of mechanical testing and structural examination of parent materials and welding consumables used for the manufacture of welded joints as well as the results of weldability and crack resistance testing for T24 steel. Possible reasons for cracking in welded joints as well as the usability of T24 steel for construction of responsible elements of waterwalls in advanced power boilers is discussed.

J Brozda

Papers

Weldability of 9Cr‐1Mo‐Nb, V P91 steel intended for service in the power industry

An investigation into the properties of the heat affected zone simulated in 9Cr‐1 Mo‐Nb, V(P91) steel intended for service at elevated temperatures

The weldability of thermomechanically rolled S460ML steel

Welding of P91 steel to other grades of steel for elevated temperature service

Problems with welding steel T24 intended for membrane walls of boilers