Laser Beam Welding of 2205 Duplex Stainless Steel with Metal Powder Additions

Abstract

Laser beam welding with the aid of metal powder additions to the weld pool was carried out to modify the ferrite/austenite (a/g) ratio of the weld metal of 2205 duplex stainless steel (DSS). The a content in the weld metal of DSS welds could be controlled by the proper flow rate of nickel powder through a coaxial nozzle. This process had the advantage of using only a small amount of filler metal, i.e. a few grams per minute of nickel powder, in the welding process. Imapct and notched tensile tests were utilized to evaluate mechanical properties of laser welds. The notched tensile test was also carried out in hydrogen under a slow displacement rate. The susceptibility to hydrogen embrittlement (HE) was estimated from the loss in notched tensile strength and correlated with the microstructure of a given laser weld. On the whole, the susceptibility to HE decreased with increasing the g content of DSS welds. Autogeneous laser welds containing the highest a content of all welds tested were most susceptible to HE. The base material with banded aϩg structures was susceptible to HE and exhibited severe secondary cracks mainly along a/g phase boundaries. Although laser welds produced at a flow rate of 3 g/min nickel powder had similar a content to the base material, they were more resistant to HE owing to randomly distributed a and g phases in the weld metal. The impact energy of laser welds at low temperatures (Ϫ75 to Ϫ100°C) along with the hardness test could also be used to check if the proper amount of nickel powder was added in laser welding of DSSs.KEY WORDS: laser beam welding; 2205 duplex stainless steel; notched tensile strength; hydrogen embrittlement.fracture separation process, which in turn depends on the microstructure and the hydrogen concentration. 10) In high strength steels, HE and stress corrosion cracking are overlapping processes.11) Hence, the resistance to hydrogen-induced crack becomes an important consideration for DSS welds to be used in hydrogen-containing environments.The purpose of this investigation was to study the microstructure and some mechanical properties of 2205 laser welds produced with the addition of nickel powder to the weld pool. The flow rate of powder was so adjusted to obtain the weld metal having nearly the same a/g ratio as the base material. In addition to the magnetic measurement of a content, impact tests of the welds at low temperatures were also employed to confirm that the proper a/g ratio in the weld metal had been achieved. Notched tensile tests in hydrogen were performed on laser-welded specimens and the results were compared to those of the base material. Experimental ProceduresThe material used in this investigation was the SAF 2205 grade purchased from AVESTA, Sweden in the form of 3.2 mm thick plates. The as-received steel plates consisted of elongated and banded structures of a and g phases. The chemical composition in mass percent was 21.1 Cr, 5.8 Ni, 2.7 Mo, 0.052 C, 1.42 Mn, 0.45 Si, 0.025 P, 0.022 S, 0.02 Cu and balance Fe.Laser welding was carried out usin...

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“…Fig. 1 shows the schematic diagram of such a nozzle, which is similar to the nozzle used in laser powder welding [14]. The spot size of a defocused laser beam at the stand-off distance, i.e.…”

Effects of Heat Input on Microstructure, Corrosion and Mechanical Characteristics of Welded Austenitic and Duplex Stainless Steels: A Review

“…In addition to austenite and ferrite, other phases may occur depending on the thermal history of the steel, when DSS is exposed to a temperature range of 300 to 1000 • C [65][66][67][68]. Examples of such phases are chromium nitrides, carbides, or carbonitride, as well as gamma-phase, chi-phase, R-phase, alpha-prime precipitation, [69][70][71][72], alpha precipitation, copper precipitates, and martensite in gamma phase. Generally, the formation of secondary phases influences the corrosion resistance and mechanical properties [73].…”

Electrochemical corrosion behavior of the laser continuous heat treatment welded joints of 2205 duplex stainless steel

“…The weld pool solidifi ed at fast cooling rate about 139 ℃/s has a desired austenite content without tradition nitrogen addition or post-weld heat treatment. H C WU et al [7] showed that laser beam welding with the aid of metal powder additions to the weld pool was carried out to modify the ferrite/austenite (α/γ) ratio of the weld metal of 2205 duplex stainless steel. In order to improve the weldability of 2205 duplex stainless steel, E Capello et al [8] had conducted a study to counterbalance the excess of δ-ferrite formed in the as-welded joint and the samples were surface treated by using the same laser source adopted during welding.…”