MICROSTRUCTURE TRANSFORMATIONS IN THE HAZ AT DISSIMILAR STEELS WELDING

Abstract

A plate of carbon steel was cladding with stainless steel by means of a shielded metal arc welding process. The alloys are considered dissimilar materials. At a welding process, is not possible to predict the final metallographic characteristics of the zones at relation with the welding process. The stainless alloy was applied at melted state therefore the high temperature affected the microstructure of carbon steel, which is called heat-affected zone. Rapid solidification of the filler metal and the rapid cooling of the heat-affected zone leaded to meta-stable microstructures formation. The changes of the microstructure at the heat-affected zone were studied by scanning electron microscopy technique. At the heat affected zone of no-aging material samples, multiple carbides of no-globular morphology were recorded, which were transformed to globular morphology after of an aging process of 3 600 hours at room temperature. Passed 10 000 hours of aging, whiskers were developed from the globular carbides.  Due to non-stoichiometric chemical composition, the multiple carbides are considered as intermetallic compounds.