Evolution Of Cr-Mo-Vweld Metal Microstructure during creep testing Part 2: P24 material

Abstract

In the course of 5^thFP “SmartWeld” EU R&D project, welding consumables of P24 grade were developed with the aim of reaching adequate combination of creep strength and fracture toughness, eventually without post-weld heat treatment. All-weld metal samples, showing evidences of “smartness” in various creep tests, were subjected to thorough metallographic and micro-analytical study, to explain changing of their properties. In particular, scanning and transmission electron microscope observations concentrated on evolution of microstructure and transformations of carbides, which were leading to nucleation of voids and cracks in various creep tests. Three different types of creep tests were carried out, i.e. the constant load short-term/ creep rupture test, the small punch accelerated creep test and the simulative (Gleeble) accelerated creep test. The transformed microstructures after these creep tests were compared with the initial microstructures of the weld metals. In this article are presented two different manual metal arc weld metals of P24 grade, in as-welded and post-weld heat-treated states, manufactured by Metrode Ltd, Chertsey, UK and by Elektrode, Jesenice, SI.