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 paper, an attempt has been made to join Hastelloy C-276 nickel-based superalloy and AISI 321 austenitic stainless steel using ERNiCrMo-4 filler.
Abstract: In the present investigation, an attempt has been made to join Hastelloy C-276 nickel-based superalloy and AISI 321 austenitic stainless steel using ERNiCrMo-4 filler. The joints were fabricated by continuous and pulsed current gas tungsten arc welding processes. Experimental studies to ascertain the structure-property co-relationship with or without pulsed current mode were carried out using an optical microscope and scanning electron microscope. Further, the energy-dispersive spectroscope was used to evaluate the extent of microsegregation. The microstructure of fusion zone was obtained as finer cellular dendritic structure for pulsed current mode, whereas columnar structure was formed with small amount of cellular structure for continuous current mode. The scanning electron microscope examination witnessed the existence of migrated grain boundaries at the weld interfaces. Moreover, the presence of secondary phases such as P and μ was observed in continuous current weld joints, whereas they were absent in pulsed current weld joints, which needs to be further characterized. Moreover, pulsed current joints resulted in narrower weld bead, refined morphology, reduced elemental segregation and improved strength of the welded joints. The outcomes of the present investigation would help in obtaining good quality dissimilar joints for industrial applications and AISI 321 ASS being cheaper consequently led to cost-effective design also.
43 citations
01 Jun 2016-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the effect of Ni-Fe buffer layered buttering and welding processes on the resulting weld joints properties has been addressed, which leads to the development of more favourable properties than observed in welded joints made using the current practice without a buffer layer.
Abstract: In this study, we present the metallurgical and mechanical investigation of four dissimilar welds between SA508Gr.3Cl.1 and SS304LN. The welding processes for buttering deposition and fill-pass welding were varied with ERNiCr-3/ENiCrFe-3 consumables. The Ni-Fe alloy buffer layer was introduced as intermediate layer in buttering and then the joints (with and without buffer layer in buttering) were fabricated. The effect of Ni-Fe buffer layered buttering and welding processes on the resulting weld joints properties has been addressed. Metallurgical and mechanical properties, fracture toughness were measured and various examinations were carried out for integrity assessment on all the weld joints. Addition of a Ni-Fe buttering layer leads to the development of more favourable properties than observed in welded joints made using the current practice without a buffer layer. Control of carbon migration and its subsequent effect on metallurgical, mechanical properties due to buffer layer has been justified in the study. Conventional procedure of DMW fabrication has been proven to be the least favourable against the new technique suggested. Modification in current integrity assessment procedure would be possible by considering the properties at interfacial regions, introduction of yield strength ratio mismatch and the plastic instability strength in the integrity assessment.
43 citations
14 Jul 2020-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the microstructure and mechanical properties of dissimilar metal weld joints between AISI 316L SS-Alloy 800 developed by activated TIG (A-TIG) welding are discussed.
Abstract: The present work discusses the microstructure and mechanical properties of dissimilar metal weld joint between AISI 316L SS-Alloy 800 developed by activated TIG (A-TIG) welding. The evolution of fusion zone microstructure and solidification temperature range were investigated through equilibrium calculation and Scheil-Gulliver equation. Electron probe micro-analysis revealed the micro-segregation of Ti and Si in the inter-dendritic arms of the fusion zone. The presence of secondary phases (Ti(C,N) and FeSi2) in the fusion zone was confirmed with X-ray diffraction technique and transmission electron microscopy of electrochemically extracted precipitates. The A-TIG weld joint showed a decent combination of tensile strength and impact toughness. Tensile testing with digital image correlation revealed a transfer of strain localization from Alloy 800 side heat affected zone to the fusion zone due to lower hardening capacity of the fusion zone. During tensile loading, the formation of micro-cracks along the solidification grain boundaries reduces the peak tensile strength of the fusion zone.
42 citations
TL;DR: In this paper, the joint region of direct diffusion-bonded joints made between duplex stainless steel SAE 2205 and medium carbon steel AISI 1035 was studied for the samples processed at temperatures of 850, 900, 950 and 975°C, with holding time of 60 and 90min and pressures of 20 and 30 MPa.
41 citations
TL;DR: In this article, the phase evolution within each weld was analyzed using thermodynamics calculation and electron back-scattered diffraction (EBSD), and it was found that the welded joints were mainly composed of martensite and ferrite phases.
41 citations
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