Title: Influences of welding processes on microstructure and mechanical properties of modified 12 wt % Cr ferritic stainless steel

Authors: A.K. Lakshminarayanan; V. Balasubramanian

Addresses: SSN College of Engineering, Kalavakkam – 603 110, Tamil Nadu, India. ' Centre for Materials Joining and Research (CEMAJOR), Annamalai University, Annamalai Nagar – 608 002, Tamil Nadu, India

Abstract: This paper presents the comparative evaluation of microstructural features and mechanical properties of a friction stir welded (solid-state), gas tungsten arc welded (fusion), electron beam and laser beam welded (high energy density) 409M grade ferritic stainless steel joints. Optical microscopy, ferritescope measurements, X-ray diffraction analysis, microhardness, transverse tensile, impact and bend tests were performed. The coarser ferrite grains in the base material are changed to very fine grains consisting duplex structure of ferrite and martensite due to the rapid cooling rate and high strain induced by severe plastic deformation caused by frictional stirring. Fine dendritic columnar grain structure of alpha ferrite with grain boundary martensite was observed in fusion zone of laser and electron beam welded joints. On the other hand, grain growth was observed in fusion zone as well as high temperature heat affected zone of gas tungsten arc welded joint resulting in deterioration of mechanical properties. [Received 17 September 2010; Revised 13 December 2010; Accepted 27 June 2011]

Keywords: ferritic stainless steel; FSS; friction stir welding; FSW; laser beam welding; electron beam welding; gas tungsten arc welding; GTAW; mechanical properties; microstructure; microhardness; plastic deformation; martensite.

DOI: 10.1504/IJMR.2012.050100

International Journal of Manufacturing Research, 2012 Vol.7 No.4, pp.331 - 353

Available online: 27 Oct 2012 *

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