Microstructural features of dissimilar welds between 316LN austenitic stainless steel and alloy 800
15 Nov 2000-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing (Elsevier)-Vol. 292, Iss: 1, pp 74-82
TL;DR: In this article, the weld fusion zones and the interfaces with the base materials were characterised in detail using light and transmission electron microscopy, showing that the stainless steel weld metals solidified dendritically, while the 16-8-2 (16%Cr-8%Ni-2%Mo) weld metal showed a predominantly cellular substructure.
Abstract: For joining type 316LN austenitic stainless steel to modified 9Cr–1Mo steel for power plant application, a trimetallic configuration using an insert piece (such as alloy 800) of intermediate thermal coefficient of expansion (CTE) has been sometimes suggested for bridging the wide gap in CTE between the two steels. Two joints are thus involved and this paper is concerned with the weld between 316LN and alloy 800. These welds were produced using three types of filler materials: austenitic stainless steels corresponding to 316, 16Cr–8Ni–2Mo, and the nickel-base Inconel 182 1 . The weld fusion zones and the interfaces with the base materials were characterised in detail using light and transmission electron microscopy. The 316 and Inconel 182 weld metals solidified dendritically, while the 16–8–2 (16%Cr–8%Ni–2%Mo) weld metal showed a predominantly cellular substructure. The Inconel weld metal contained a large number of inclusions when deposited from flux-coated electrodes, but was relatively inclusion-free under inert gas-shielded welding. Long-term elevated-temperature aging of the weld metals resulted in embrittling sigma phase precipitation in the austenitic stainless steel weld metals, but the nickel-base welds showed no visible precipitation, demonstrating their superior metallurgical stability for high-temperature service.
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TL;DR: In this article, the effects of creep behavior of different weld joints at various test conditions and parameters involved were analyzed for fast breeder reactors, steam generators, and prototype FBRs.
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TL;DR: In this article, the authors studied the characteristics of 316LN welded joints produced by different welding fillers through temperature and field dependent magnetization measurements and observed significant variations depending on the used welding filler.
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TL;DR: In this article, a super Ni laminated composite and 1Cr18Ni9Ti stainless steel were welded by the tungsten inert gas process with the Cr25-Ni13 filler alloy, and microstructure, element distribution and phase formation near the fusion zone were evaluated by standard technique.
Abstract: Super Ni laminated composite and 1Cr18Ni9Ti stainless steel were welded by the tungsten inert gas process with the Cr25–Ni13 filler alloy The microstructure, element distribution and phase formation near the fusion zone were evaluated by standard technique Results indicated the formation of four main regions: the fusion transition region on the 1Cr18Ni9Ti steel side, the fusion transition region on the super Ni laminated composite side, a columnar crystal weld region and the weld centre region The microstructure on either side of the weld was characterized by strong directionality and changed from columnar austenite to equiaxed austenite in the weld centre A Ni, Fe and Cr element transition region, about 30 μm wide, was formed at the fusion zone on the super Ni side The phase formed into welded zone was composed mainly of austenite, δ-Fe, γ-Ni(Cr, Fe) and FeNi intermetallic compounds
7 citations
TL;DR: In this article, the relationship between the microstructure and mechanical properties of Inconel 617/AISI 310 stainless steel electron beam welds was analyzed using scanning electron microscopy and the electron backscatter diffraction (EBSD) technique.
Abstract: The aim of this research was to analyze the relationship between the microstructure and mechanical properties of Inconel 617/AISI 310 stainless steel electron beam welds. The microstructure of the weldments was studied using scanning electron microscopy and the electron backscatter diffraction (EBSD) technique. Mechanical properties of the weldments, including tensile behavior, hardness and impact toughness resistance, were evaluated. The results indicated that the electron beam welding process led to the segregation of elements in the weld metals, and the formation of secondary phases rich in Co, Nb and Mo was recorded too. EBSD studies also showed that the grains of the weldment had a variety of orientations. In addition, the fraction of coincident-site lattice boundaries was non-uniformly distributed across the weldments. The tensile strength of the weldments was similar to that of the AISI 310 parent metal, and the tensile samples underwent the ductile fracture mode. Upon Charpy impact testing, the weldments underwent notch deformation and the ductile mode of fracture; however, the impact toughness resistance was lower, as compared with the base metals. Based on the performed tests, the heat input of 168 kJ/m could be recommended.
7 citations
TL;DR: In this article, an attempt has been made to weld nickel-based superalloy, Inconel 718 and ferritic stainless steel, AISI 430, using a gas tungsten arc welding process employing ER2553 and ERNiCrMo-4 fillers.
Abstract: In this research work, an attempt has been made to weld nickel-based superalloy, Inconel 718 and ferritic stainless steel, AISI 430, using a gas tungsten arc welding process employing ER2553 and ERNiCrMo-4 fillers. Microstructure studies revealed the formation of an unmixed zone and the presence of tiny Nb-rich phases in the heat-affected zone (HAZ) of Inconel 718; also, grain coarsening was observed at the HAZ of AISI 430. Tensile studies corroborated that the failures occurred at the parent metal of AISI 430 in all the experimental trials. Bend test results revealed that no cracks occurred in either of the weldments reporting for ductility and soundness of the weld joints. This work also articulates the detailed structure–property relationships of these dissimilar weldments using the combined techniques of optical and scanning electron microscopy. The outcomes of the present study will be helpful to the aerospace and nuclear sectors.
7 citations
Cites methods from "Microstructural features of dissimi..."
...[10] recommended the use of Inconel filler metals for joining the trimetallic joints involving ferritic steel, AISI 316 LN and Alloy 800 joints....
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References
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01 Oct 1988
TL;DR: In this article, the importance of the Constitution diagram for the understanding of Welding Phenomena is discussed, and a detailed description of the Welding and post-weld surface treatment of Fabrications and Welded Components made from Austenitic Stainless Steels is given.
Abstract: Contents: Significance of Constitution Diagrams for the Understanding of Welding Phenomena * Metallurgical Processes During Solidification and Cooling in Stainless Steel Weld Metal * Metallurgical Phenomena in Secondary Crystallization of Stainless Steels and Weld Metals * Precipitation Phenomena in Stainless Steel and Weld Metals * Hot Cracking Resistance During the Welding of Austenitic Stainless Steels * Welding Metallurgy of Ferritic Stainless Chromium Steels with Carbon Contents Below 0.15 per cent * Welding Metallurgy of Low Carbon Chromium-Nickel Martensitic Stainless Steels (Soft Martensitic Steels) * Welding Metallurgy of Duplex Austenitic-Ferritic Stainless Steels * Welding Metallurgy of Austenitic Stainless Steels * General Instructions for the Welding and Post-Weld Surface Treatments of Fabrications and Welded Components Made from Austenitic Stainless Steel * Welding Metallurgy of Heat Resisting Steels * Welding Metallurgy of Austenitic-Ferritic Dissimilar Joints * Appendix: Abbreviations and Short Designations * References * Author Index * Subject Index.
394 citations
TL;DR: In this article, a trimetallic joint involving modified 9Cr-1Mo steel and 316LN austenitic stainless steel as the base materials and Alloy 800 as the intermediate piece was investigated.
150 citations
TL;DR: In this paper, a wide range of fundamental knowledge of solidification processes is applied to the study of fusion-weld solidification, including inoculants, stimulated surface nucleation, dynamic grain refinement, and arc modulation.
Abstract: To an increasing extent the wide range of fundamental knowledge of solidification processes is being applied to the study of fusion-weld solidification. Initially this fundamental knowledge is surveyed concisely and those areas of particular importance to weld-pool solidification are indentified. This is followed by an examination of phenomenological studies of the solidification behaviour of fusion welds in which particular attention is given to factors influencing the development of the fusion-zone structure. Then, the ways in which the metallurgical structure of the fusion zone influences the mechanical properties of the weldment are reviewed. Attention is then given to methods of controlling the fusion-zone structure by using inoculants, stimulated surface nucleation, dynamic grain refinement, and arc modulation. The gains and advantages which accrue from the way in which structure control affects properties are then considered. The review concludes with a discussion of likely future developme...
119 citations
TL;DR: In this paper, a ternary system composed of a pure iron substrate and a 70Ni-30Cu filler metal was used to determine the nature and evolution of boundaries and structure in dissimilar metal welds.
Abstract: Cracking, or disbonding, along the fusion boundary in dissimilar metal welds has been a persistent problem, particularly in applications where austenitic alloys are clad on to structural steels for corrosion protection. Many failures in dissimilar metal welds occur as a result of cracking along a boundary that runs parallel to the fusion boundary in the adjacent weld metal. A preliminary investigation was undertaken to determine the nature and evolution of boundaries and structure in dissimilar metal welds using a simple ternary system composed of a pure iron substrate and a 70Ni–30Cu (Monel) filler metal. Changes in base metal dilution were found to alter the evolution of boundaries and structures near the fusion boundary dramatically. Optical metallography and electron microanalysis reveal that the resulting weld microstructures and boundaries are similar to those observed in engineering materials used for cladding and corrosion resistant overlay. Transmission electron diffraction analysis revea...
63 citations
TL;DR: In this article, a series of laser and gas tungsten arc welds traversing stainless steels of different chemical compositions has been studied, to elucidate the role of austenite or ferrite nucleation and cooling rate on solidification behaviour.
Abstract: A series of laser and gas tungsten arc welds traversing stainless steels of different chemical compositions has been studied, to elucidate the role of austenite or ferrite nucleation and cooling rate on solidification behaviour. It has been found that a steel with a high CrEQ/NiEQ ratio can be induced to solidify as metastable austenite by initiating the weld in a steel with a lower CrEQ/NiEQ ratio in which the thermodynamically stable solidification mode is austenitic. The austenite dendrites are then found to continue growth across the weld junction into the undiluted regions of the high CrEQ/NiEQ ratio material. By providing austenite particles in this way, nucleation is rendered unnecessary and it is found that solidification to metastable austenite can be induced at cooling rates significantly lower than previously encountered. The results of these and other experiments in which the welding speed was changed during the experiment are interpreted to yield new information about the mechanisms o...
37 citations