Contents lists available at ScienceDirect Materials Characterization journal homepage: www.elsevier.com/locate/matchar Evaluation of microstructural and mechanical properties of Fe-16Cr-1Ni- 9Mn-0.12N austenitic stainless steel welded joints Manidipto Mukherjee a,⁎ , Tapan Kumar Pal b a Mechanical Engineering Department, SRM University, Chennai 603203, Tamil Nadu, India b Metallurgical and Material Engineering Department, Jadavpur University, Kolkata 700032, India ARTICLE INFO Keywords: Low nickel austenitic stainless steel Modes of metal transfer Microstructure Mechanical behaviour ABSTRACT This study has been aimed to find out the proper welding procedure/conditions for a newly developed Fe-16Cr- 1Ni-9Mn-0.12N austenitic stainless steel (ASS), which is uniquely modified from 200 series alloy, in order to control the microstructural metastability of the weld metals. The welded joints of 4 mm thick sheet were pre- pared in a square butt configuration by using three modes of metal transfer, i.e., short-circuit (SC), spray (S), and pulse (P) mode of metal transfer and three austenitic filler metals (304L, 308L and 316L) under two shielding gas environments using gas metal arc welding (GMAW) process. It is observed that the variation in modes of metal transfer and filler metals can effectively manipulate the metastability of γ-phase, formation of δ-phase and grain size of the weld metals. Among the modes of metal transfer, pulse mode of metal transfer produces more me- tastable γ-phase and higher δ-phase fraction responsible for finer grain structure in weld metals irrespective of filler metals used. Again, higher microstructural metastability was obtained with the 304L filler metal irre- spective of modes of metal transfer used. It is evident that the weld metals having higher microstructural me- tastability also improved mechanical properties (i.e. hardness, strength and toughness). However, weak fusion boundary (FB) region of welded joint limits the beneficial effect of metastability and creates a weakest link in the joint. On the other hand, high temperature heat affected zone (HTHAZ) having a coarse austenite grain sur- rounded by grain boundary precipitates is governed only by the modes of metal transfer. 1. Introduction The relatively high cost of nickel as an alloying element in standard austenitic stainless steels (which contain 8 to 12 wt per cent nickel) [1] is the main driving force behind the development of low nickel auste- nitic stainless steel (LNiASS) where a combination of Mn and N has been adopted as substitutes. Manganese partially stabilizes the γ-phase and increases the solubility of N in the liquid steel which acts as a potent austenite former and reduces the tendency to form ferrite during solidification and deformation-induced α′ and ε martensites under stress [2–4]. A comprehensive study by Nijhawan et al. has shown that low nickel Cr-Mn-N steels also known as LNiASS containing up to 15 wt per cent Mn and 0.6 wt per cent N have properties comparable with AISI 304, and are successfully applied in household utensils, motor car and railway fittings, hospital ware, dairy equipment, cryogenic pro- cesses, chemical equipment and pressure vessels [5]. However, welding is the most common method for fabricating stainless steel structures in different applications [6]. Austenitic stainless steels generally experi- ence severe metallurgical changes during welding such as stability of γ- phase, grain coarsening in the heat affected zone (HAZ), formation of martensite, precipitation of carbides and nitrides, sensitisation, HAZ softening, cracking, weld decay etc. which will affect the mechanical behaviour of the welded joints and will ultimately govern the service life of the welded structures/components [7–10]. Among the various welding techniques, gas metal arc welding (GMAW) process is now the most reliable, cost-effective, techno-eco- nomic and widely practiced method in most industries due to its high productivity, relative cleanliness, ability to weld complicated shapes with large and small dimensions and availability of a wide range of filler materials [11]. GMAW process involves various operating char- acteristics such as mode of metal transfer, filler metals, shielding gas composition etc. which play important role on the performance of welded joints. This welding process could be operated at a particular mode among four different modes of metal transfer such as short cir- cuit, globular, spray and pulse [7–10,12,13]. However, globular mode of metal transfer is often avoided because of heavy spatter generation (large droplet diameter) during welding which severely deteriorates the weld bead appearance and quality [10]. The effect of other modes of http://dx.doi.org/10.1016/j.matchar.2017.07.028 Received 22 December 2016; Received in revised form 22 June 2017; Accepted 16 July 2017 ⁎ Corresponding author. E-mail address: m.mukherjee.ju@gmail.com (M. Mukherjee). Materials Characterization 131 (2017) 406–424 Available online 18 July 2017 1044-5803/ © 2017 Elsevier Inc. All rights reserved. MARK