Abstract
The excellent corrosion resistance of superaustenitic stainless steel (SASS) alloys has been shown to be a direct consequence of high concentrations of Mo. The presence of Mo can have a significant effect on the microstructural development of welds in these alloys. In this research, the microstructural development of welds in the Fe-Ni-Cr-Mo system was analyzed over a wide variety of Cr/Ni ratios and Mo contents. The system was first simulated by construction of multi-component phase diagrams using the CALPHAD technique. Data gleaned from vertical sections of these diagrams were inserted in the compositional range of a liquidus projection to produce diagrams that can be used as a guide to understand the influence of composition on microstructural development. A large number of experimental alloys were then prepared via arc-button melting for comparison with the diagrams. Each button was characterized using various microscopy techniques. The expected δ-ferrite and γ-austenite phases were accompanied by martensite at low Cr/Ni ratios and by σ-phase at high Mo contents. The results were used to construct a map of expected phase transformation sequence and resultant microstructures as a function of composition. Electron microprobe measurements of selected alloys were performed to compare the distribution of Mo solute between different solidification modes. Severe Mo microsegregation was observed in alloys that solidified directly as austenite; this was attributed to the low diffusivity of Mo in austenite. The level of Mo microsegregation could be significantly reduced in alloys that solidified as δ-ferrite first and subsequently transformed to austenite by a solid state transformation. Magnetic ferrite measurements were also used to produce quantitative relationships between alloy composition and ferrite content, and the results were then plotted on the WRC-1992 diagram. The results of this work provide a working guideline for future base metal and filler metal development of these alloys.
Article PDF
Similar content being viewed by others
Avoid common mistakes on your manuscript.
References
Garner A.: The effect of autogenous welding on chloride pitting corrosion in austenitic stainless steels, Corrosion 35, 1979, 108–114.
Banovic S., DuPont J., Marder A.: Dilution and microsegregation in dissimilar metal welds between super austenitic stainless steel and nickel base alloys, Science and Technology of Welding and Joining (UK) 7, 2002, 374–383.
DuPont J., Friedersdorf L., Marder A., Banovic S.: Weldability and corrosion performance of welds in AL-6XN Superaustenitic Stainless Steel, Lehigh University ATLSS Report No. 01–03, 2001.
Brooks J., Thompson A.: Microstructural development and solidification cracking susceptibility of austenitic stainless steel welds, International Materials Reviews 36, 1991, 16–44.
Banovic S., DuPont J., Marder A.: Dilution control in gas tungsten arc welds involving superaustentic stainless steels and nickel based alloys, Metallurgical and Material Transactions 32B, 2001, 1171–1176.
Banovic S., DuPont J., Marder A.: Microstructural evolution and weldability of dissimilar welds between a super austenitic stainless steel and nickel-based alloys, Welding Journal 82, 2003, 125–135.
Sundman B.: Thermo-Calc. S-100 44 [N], 2001, Stockholm, Sweden, Department of Materials Science and Engineering, KTH.
Saunders N.: Fe-Data Thermodynamic Database, [3.0], 2001, The Surrey Research Park, Guildford, UK, Thermotech, Ltd.
Schaeffler A.: Constitution diagram for stainless steel weld metal, Metals Progress 56, 1949, 680–680B.
Elmer J., Allen S., Eagar T.: Microstructural development during solidification of stainless steel alloys, Metallurgical Transactions A 20A, 1989, 2117–2131.
Heinrich K., Myklebust R.L., Yakowitz H., Rasberry S.D.: Simple correction procedure for quantitative electronprobe microanalysis, NBS Technical Note 719, 1972, 1–31.
Koseki T., Ogawa T.: An Investigation of Weld Solidification in Cr-Ni-Fe-Mo Alloys. Welding International 6, 1992, 516–522.
Dr. Matthew J. Perricone: Effect of composition, cooling rate, and solidification velocity on the microstructural development of mo-bearing stainless steels, Thesis, Lehigh University.
Kurdjumov G., Sachs G.Z., Physics 64, 1930, 325–343.
Seferian D.: Métallurgie de la Soudure, 1959.
Kotecki D.: A Martensite Boundary on the WRC-1992 Diagram. Welding Journal 78, 2000, 180–192.
McCowan C., Siewart T., Olson D.: Stainless Steel Weld Metal: Prediction of Ferrite Content, Bulletin 342, 1989, Welding Research Council, Welding Research Council Bulletin.
Author information
Authors and Affiliations
Additional information
Advisor: Prof. J.N. DuPont.
Rights and permissions
About this article
Cite this article
Anderson, T. Henry Granjon Prize Competition 2006 Winner, Category B “Materials behaviour and weldability” The Influence of Molybdenum on the Microstructure of Stainless Steel Welds. Weld World 50, 23–34 (2006). https://doi.org/10.1007/BF03263442
Published:
Issue Date:
DOI: https://doi.org/10.1007/BF03263442