Caracterização microestrutural e avaliação do perfil de microdureza da interface AISI 8630M amanteigado com o arame AWS ER 80S.

Abstract

Underwater valves are manufactured with AISI 8630M steel and are welded to oil extraction pipes. In this context, the high pressures and low temperatures allied with fragile microstructure present in the welding region together with the deleterious effect of hydrogen, can use the mechanical failure of these devices in use. The Butterion of 8630M steel with low carbon steel appears as an alternative to the embrittlement of hydrogen in marine environment, since it is not expected formation of fragile partialy diluted descontinous areas in the microstructure of the 8630M/low carbon steel interface. The objective of this work was to evaluate the microstructure and the microhardness profile of the buttering interface of the AISI 8630M steel with the addition metal AWS ER 80S using the GMAW (Gas Metal Arc Welding) welding process, to evaluate the effect of the heat treatment of strain relief, and to compare the microstructure formed with that generated in the buttering of the AISI 8630M steel with the Inconel 625 Ni alloy. Thus, samples were cut and prepared before and after the butterring and subjected to analysis by optical microscopy, scanning electrical microscopy (SEM) and microhardness. It was observed that the TTAT practically did not change the microstructure, but it was efficient in reducing the microhardness along the interface, also a microstructure without the presence of partially diluted zones.