Ref.: MmeMge20-001
Apresentador: Lívia Ferreira Guedes
Autores (Instituição): Guedes, L.F.(Universidade Federal Fluminense); Tavares, S.S.(Universidade Federal Fluminense); de Sousa, E.M.(Universidade Federal do Piauí); De Sousa, R.R.(Universidade Federal do Piauí); Velasco, J.A.(Instituto Nacional de Tecnologia); CINDRA-FONSECA, M.(Universidade Federal Fluminense);
Resumo:
Supermartensitic stainless steels (SMSS) are corrosion resistant alloys used as casing and
tubulars in the oil and gas prodution. In this application, mandrels for gas or chemical
products injection in the wheel are composed of forged and hot rolled seamless tubes.
SMSSs used as tubulars are subjected to sulfide stress corrosion cracking (SSC) in sour
services with H 2 S and high salinity. Nitriding is a thermochemical treatment used to increase
hardness and wear resistance of steels. This surface treatment can be used to improve the
performance of SMSSs. In this work a forged SMSS grade UNS S41426 steel was plasma
nitrided at 350 º C, 400 º C and 570 º C for 5 h, using gas mixture of 75%H 2 and 25%N 2 . The
effects of the microstructure were evaluated by X-ray diffraction and scanning electron
microscopy. The effects on mechanical properties were evaluated by microhardness and
tensile tests, while the susceptibility to SSC was evaluated by slow strain rate testing
(SSRT). The average microhardness measured in the surface was 308 HV0.05 in the as
received steel, and increased to 341 HV0.05, 441 HV0.05 and 1277 HV0.05 with nitriding at
350 o C, 400 o C and 570 o C, respectivelly. The results were compared to specimens of SMSS not
subjected to nitriding treatment.