Bonding by hot extrusion of Incoloy 825 and Duplex 2205 to low alloy steel

Abstract

Low alloy AISI 4130 steel has been bonded to an Incoloy 825 and a Duplex 2205 stainless steel by an industrial hot extrusion process, the final product being a seamless clad tube, with an internal lining of these corrosion resistant alloys. The microstructures of the as processed products have been analysed using optical metallography and scanning (SEM) and scanning transmission (STEM) electron microscopy. The interdiffusion of various elements through the interface has been determined using microanalysis both in the SEM and the STEM. For the combination AISI 4130–Incoloy 825, a region close to the original interface on the Incoloy side is observed, in which a deformation substructure with subgrains, dislocations, and a considerable number of M₂₃C₆ type carbides is found. Various layers of austenite free of carbides, martensite, and ferrite–pearlite are observed on the steel side. For the combination AISI 4130–Duplex 2205, a region close to the interface, having a small amount of ferrite and a profusion of M₂₃C₆ carbides precipitated at the grain boundaries, is observed; this is succeeded by regions having a greater amount of ferrite at grain boundaries until the original structure of the Duplex is attained. The influence of various heat treatments, consisting of quenching plus tempering of the region around the bonding, has also been analysed.

MST/1325