Avaliação da susceptibilidade à fragilização por hidrogênio de juntas soldadas e metais dissimilares para aplicações submarinas no setor de petróleo e gás.

Abstract

This work aimed to study the susceptibility to hydrogen embrittlement of dissimilar welded joints, used in offshore sector of oil industry. For this weld beads were previously deposited in segments of quenched and tempered AISI 8630 steel used in submarine valve, with two different composition (standard and modified) using the automatized GMAW process. AWS ERNiCrMo-3 wire with 1.2 mm diameter commercially known as Inconel 625, was used as filer metal. The segments were subsequently subjected to post welding heat treatment (PWHT) at 650 ° C for 3 hours and 676 ° C for 1h. After this the samples were subjected to welding union, also using the same wire and welding process. After welding union tension samples were drawn for hydrogenation test using the same condition of cathodic protection used in submarine application. The test samples were subjected to hydrogenation by seven days, and then immediately were placed in the tensile test to evaluate as hydrogen inserted into the microstructure affects its mechanical properties. The results showed that thermal cycle of the PWHT promote a significative influence. It was also observed that the PWHT 650 ° C for 3 hours promoted a greater formation of partially diluted areas, making the microstructure of the region next to the fusion line harder. The specimens machined from the standard AISI 8630 showed higher susceptibility to hydrogen embrittlement.