Stress Corrosion Cracking Resistance of 22%Cr Duplex Stainless Steel in Simulated Sour Environments

Abstract

Effect of nickel and nitrogen contents on stress corrosion cracking (SCC) of 22%Cr-3%Mo-base duplex stainless steel was investigated in simulated sour environments with respect to both the base metal and the heat-affected zone (HAZ) of welding. The threshold stress and the critica) chloride concentration for SCC ware evaluated as a function of the ferrite content (a-content) in the alloy. The threshold stress is highest at the a-content of 40 to 45%, and is lowered with decreasing and increasing the a-content from its value. The alloy whose a-content exceeds 80% at the HAZ has also high susceptibilities to pitting corrosion and intergranular corrosion (IGC). The critica) chloride concentration for cracking increases with the decrease in the a-content. Moreover, the contents of chromium, nickel and molybdenum in the a-phase are considered to be an important factor for determining the critica) chloride concentration.KEY WORDS: duplex stainless steel, sour environment, stress corrosion cracking. ABSTRACTThe effect of Cr, Ni, and Mo contents of Ni-base alloy on the corrosion behavior in H2S-0O2-C1 environment with elemental sulfur at elevated temperature was investigated. The environmental with elemental sulfur was more corrosive than that without elemental sulfur. The stress corrosion cracking (SSC) resistance of Ni-base alloys increases with increasing Ni and especially Mo contents. The main effect of the elemental sulfur is considered that the generation of H2S due to the cathodic reaction of elemental sulfur at a location underneath sulfur deposftion, which is related to the viscosity of elemental sulfur. Recommendable chemical composition of Ni-base alloys in H2S-CO2-C1--S environment was proposed trom the view points of phase stability, stress corrosion cracking, and hydrogen embrittlement (HE). Suitable high-Ni alloys had more than 12%Mo and 15%Cr and the phase stability parameter (Md) value below 0.911.

Avaliação da soldagem multipasse de chapas espessas de aços inoxidáveis lean duplex UNS S32304 soldadas pelos processos SMAW, GMAW e FCAW: parte 1: propriedades mecânicas

“…Ressalta-se que a adição de nitrogênio no gás de proteção no processo GMAW é importante para evitar a perda de nitrogênio, conforme descrito por Westin [10], e por conseqüência a formação excessiva de ferrita em detrimento da austenita. Entretanto para o a soldagem FCAW acredita-se que tal adição não se faz necessária, devido a presença da escória, que ao se solidificar a uma temperatura mais elevada, portanto, primeiro que a poça de fusão, pode atuar como uma barreira à perda de N 2 .…”

“…As propriedades do metal depositado, como resistência, tenacidade e resistência à corrosão podem ser prejudicadas por um excessivo desvio no balanço de fases com relação ao metal base [9,10].…”

Effect of N addition on tensile and corrosion behaviors of CD4MCU cast duplex stainless steels

“…[2,7,[9][10][11] Particularly, the importance of nitrogen-containing duplex stainless steels is continuously growing due to their unique advantages. [7,9] Nitrogen alloying, however, offers challenges since the solubility of N in Fe-based alloy is extremely limited at atmospheric pressure, and most of the nitrogen-related research on duplex stainless steel has been performed on the wrought products. [3,[5][6][7]9] At present, a limited number of studies have been reported on cast products of duplex stainless steels, despite their significance in the industry.…”

“…[1][2][3][4][5][6][7][8] Recent development of duplex stainless steels occurs mainly in the area of alloying Mo, Cu, N, etc. for further improving mechanical and corrosion properties.…”

“…for further improving mechanical and corrosion properties. [2,7,[9][10][11] Particularly, the importance of nitrogen-containing duplex stainless steels is continuously growing due to their unique advantages. [7,9] Nitrogen alloying, however, offers challenges since the solubility of N in Fe-based alloy is extremely limited at atmospheric pressure, and most of the nitrogen-related research on duplex stainless steel has been performed on the wrought products.…”