Characterization of welded joint made of T24 steel (7CrMoVTiB10-10) with and without post-weld heat treatment

Abstract

Modified 2.25Cr1Mo steel, known as a relatively new generation, grade T24 heat resistant steel (7CrMoVTiB10- 10), is extensively used as a material for fabrication of water walls panels - evaporator tubes in supercritical boilers of a new generation in thermal power plants. A special advantage of T24 steel is low carbon content and the optimal content of alloying element which simultaneously provides its good weldability and heat resistance. For elements up to 10 mm of thickness, made of T24 steel standards not foreseen previous and subsequent post-weld heat treatment (PWHT). However, after a series of problems encountered with welded joints, practice has shown that some kind of heat treatment is necessary, in order to reduce the susceptibility to hydrogen induced stress corrosion cracking (HISCC). This paper deals with the microstructural characterization of both base material and welded joint of boiler tube (dimension �����44,5x7,1 mm), made of T24 steel, before and after PWHT. The aim of this paper is to evaluate the effect of this type of PWHT on microstructural changes and its possible impact on the susceptibility to cracking of T24 welded joints.