Surface working of 304L stainless steel: Impact on microstructure, electrochemical behavior and SCC resistance S.G. Acharyya a, ⁎ , A. Khandelwal b , V. Kain a , A. Kumar c , I. Samajdar c a Materials Science Division, Bhabha Atomic Research Center, Mumbai, India b Visvesvaraya National Institute of Technology, Nagpur, India c Department of Metallurgical Engineering and Materials Science, IIT Bombay, Mumbai, India ARTICLE DATA ABSTRACT Article history: Received 8 May 2012 Received in revised form 5 July 2012 Accepted 9 July 2012 The effect of surface working operations on the microstructure, electrochemical behavior and stress corrosion cracking resistance of 304L stainless steel (SS) was investigated in this study. The material was subjected to (a) solution annealing (b) machining and (c) grinding operations. Microstructural characterization was done using stereo microscopy and electron back scattered diffraction (EBSD) technique. The electrochemical nature of the surfaces in machined, ground and solution annealed condition were studied using potentiodynamic polarization and scanning electrochemical microscopy (SECM) in borate buffer solution. The stress corrosion cracking resistance of 304L SS in different conditions was studied by exposing the samples to boiling MgCl 2 environment. Results revealed that the heavy plastic deformation and residual stresses present near the surface due to machining and grinding operations make 304L SS electrochemically more active and susceptible to stress corrosion cracking. Ground sample showed highest magnitude of current density in the passive potential range followed by machined and solution annealed 304L SS. Micro-electrochemical studies established that surface working promotes localized corrosion along the surface asperities which could lead to crack initiation. © 2012 Elsevier Inc. All rights reserved. Keywords: Machining Grinding Residual stresses Stress corrosion cracking SECM 1. Introduction Surface integrity issues arising due to material finishing pro- cesses have become a serious cause of concern in fabrication of stainless steel components [1–12]. Surface finishing oper- ations like machining grinding produce very high levels of tensile residual stresses on the metal surface (of the order of 1100 MPa [1]) together with the creation of a work hardened layer having high magnitude of plastic deformation [4–10], stress and strain induced martensite formation [8,9] and heavy grain fragmentation [8–14]. Moreover, surface finishing operations increase the surface roughness of stainless steel which has direct implication on its electrochemical behavior [3,15–17]. Higher surface roughness implies the presence of deeper grooves on the surface wherein higher concentration of ions take place leading to early initiation of attack [18]. The nature of the surface exposed to service environment plays a vital role in determining its integrity as attack initiates from the surface of the metal exposed to the environment. Thus extensive efforts are being directed towards producing surface integrity parameters such as surface roughness, hardness, depth of work hardened layer and the associated residual stresses in a range of surface finishing operations such as turning, milling, grinding, electro discharge machining (EDM) etc. [4,19–23]. Also attempts have been made to correlate the process parameters of surface finishing operations and the surface integrity measures like hardness, residual stresses, and surface roughness [4,5,19]. Localized corrosion, especially stress corrosion cracking becomes a major issue when the performances of components fabricated of stainless steel are MATERIALS CHARACTERIZATION 72 (2012) 68 – 76 ⁎ Corresponding author. Tel.: + 91 9969628176; fax: + 91 25505151. E-mail address: swati364@gmail.com (S.G. Acharyya). 1044-5803/$ – see front matter © 2012 Elsevier Inc. All rights reserved. doi:10.1016/j.matchar.2012.07.008 Available online at www.sciencedirect.com www.elsevier.com/locate/matchar