Effects of Thermal Aging on Microstructure and Corrosion Resistance of AISI 317L Steel Weld Metal in the FSW Process

Abstract

The AISI 317L grade is an austenitic stainless steel with high Mo content (3.0 wt% min.). Due to the higher pitting resistance, this grade has replaced AISI 316L steel in many applications where the corrosion resistance is a critical property. However, the high Mo can induce phase transformations in high temperature services. In modern oil refinaries and petrochemical industries AISI 317L has been selected for temperatures as high as 550 °C. The goal of this work was to analyze the microstructural evolution and corrosion resistance of base and weld metal of AISI 317L stainless steel. The welded joints were produced by friction stir welding (FSW). The effect of prolonged exposure at 550 °C was investigated in specimens aged for 200h, 300h and 400h. After each aging treatment microstructural characterization was performed by scanning electron microscopy (SEM). Double loop electrochemical polarization reactivation tests (DL-EPR) were performed to evaluate the degree of sensitization of the samples. The results indicated that the increase of the exposure time at 550 °C promotes the formation of intermetallic phases, which causes corrosion decay of the weld metal.

Influence of the heat input and aging treatment on microstructure and mechanical properties of AISI 317 L steel weldments using 0020 robotic–pulsed GMAW

“…Since Mo is ferritizing, the higher concentration of this element in AISI 317L steel when compared with others austenitic stainless steels will increase the tendency to form δ-ferrite in the fusion zone [11]. Higher δ-ferrite formation associated with higher concentration of Mo contributes to a greater tendency towards precipitation of deleterious phases such as sigma (σ) and chi (χ) [3] Although some previous works [3,4,11] have predicted microstructural and property changes on AISI 317L, very few articles were published considering the influence of the robotic-pulsed GMAW process on the microstructure and mechanical properties of this steel. It is worthwhile mentioning that the robotic-pulsed GMAW process allows a much better control of the welding parameters, arc stability, and heat input as well as a high productivity rate and low operation cost in comparison with the semi-automatic process [12].…”

“…Previous works [3][4][5] has reported that AISI 317L steel also presents a higher resistance to sensitization during welding or when applied to thermal processes due to its low carbon content and that the combination of molybdenum and nitrogen in the chemical composition of this steel is particularly effective in increasing resistance to pitting and cracking, especially in acidic media-containing chlorides and sulfur compounds at elevated temperatures.…”

“…Because all these attributes, AISI 317L stainless steel is often used as lining plates in heavy oil processing towers and as corrosion protective layer over the substrate (weld cladding) in several components, in order to make them resistant to the action of the severe corrosive environment [4,5].…”

Karakteristik Daktilitas SS304 Yang Teroksidasi Pada Temperatur Tinggi

“…Perubahan fasa yang terjadi ketika waktu proses selama 2 jam dengan kondisi pendinginan alamiah memiliki mekanisme yang berbeda. Mekanisme yang terjadi adalah pembentukan fasa alpha, perubahan martensit dan juga terjadi rekristalisasi [8,9]. Hal ini yang menyebabkan kekerasan sampel SS304 yang diproses dengan waktu selama 2 jam lebih tinggi dibandingkan yang diproses selama 1 jam.…”

Machining of Difficult-To-Cut Materials

“…Nevertheless, main application of these materials is for pipes and fittings for the water supply of apartments and houses [5,6]. Some petrochemical applications use the austenitic steel AISI 317L or the relatively new P750 for clads, vessels, tubes, valves and other components in oil refineries [7].…”