Ensaios e metodologias de análise de integridade para equipamentos em aço baixa liga sujeitos à fragilização por hidrogênio

Abstract

This research work presents initially a review of environmentally assisted cracking mechanics, especially hydrogen embrittlement of low alloy steels. Applicability of structural integrity and fitness for service techniques based on fracture mechanics for this scenario is discussed together with different testing methodologies in order to obtain useful parameters. Rising step loading tests were performed to obtain fracture toughness values of a 780 MPa yield strength quenched and tempered AISI 4340 low alloy steel in brine solution with cathodic protection. Results obtained were discussed vis à vis available literature, showing good correlation. They were then employed in a structural integrity analysis according to fitness for service standard British Standard 7910 (2013), proving the suitability of this methodology to evaluate the integrity of equipment and components subject to hydrogen embrittlement. The capability to perform fitness for service evaluations in aggressive environments with reliable fracture toughness data allows the safe operation of hard-to-inspect/repair equipment (namely subsea), thus avoiding production losses, environmental hazards and costly interventions.