Effect of Hydrogen on the Mechanical Properties of ASTM A182 F22 and ASTM A36 Steels Welded Joint Using Inconel 625 as Filler and Buttering Metal

Abstract

ASTM A 182 F22 steel, used in components subsea for oil extraction, are previously buttered with ductile metal such as Inconel 625, before being welded to steel pipes similar to ASTM A36 steels. The thermal buttering weld cycle provides the formation of high hardness micro-phases and carbides at the interface between F22 steel and the buttering with Inconel, which when in contact with hydrogen, originating from the cathodic protection applied to these equipment, can lead to the embrittlement of this region, causing fragile fractures. In this work, ASTM A 182 F22 steel, buttered with Inconel 625 and welded to A36 steel, submitted to post-weld heat treatment without hydrogenation and subjected to cathodic protection for hydrogen permeation were submitted to fracture toughness test. The welds and buttering were done using GMAW process with AWS ERNiCrMo-3 wire as filler and buttering metal and a mixture of Ar and He as shield gas. The results indicated a 56% of area reduction, and 15% in the elongation values in the tensile tests, in addition to a 13.3% reduction in the CTOD value, for welded joints subjected to hydrogen permeation, which showed a quasi-cleavage fracture mechanism.