Abstract
In the present work, AISI 304L steel was used to investigate the effect of surface mechanical attrition treatment (SMAT) parameters on the hardness and microstructure. The surface modified by SMAT was examined using an optical microscope, SEM, electron backscattered diffraction, X-ray diffraction and microhardness measurements. The surface hardness of specimens was more than two times the hardness of non-treated core for all SMAT parameters. High density of shear bands (which formed nanosize rhombic blocks) was observed near the treated specimen surface. Density of shear bands was reliant on the size and number of balls. Deformation induced martensite (α′) was formed in surface mechanical attrition treated region. Volume per cent of α′ was enhanced with an increase in SMAT duration and number of balls. However, it was reduced with an increase in gap between vibrating plate and specimen surface. Microstructure evolution at various SMAT parameters was effectively explained using newly introduced terminology called ‘peening intensity’.
Acknowledgements
We would like to thank Dr R. Kadam of Kalyani Centre for Technology and Innovation, Bharat Forge Ltd, Pune, India, for his cooperation in SEM and EBSD experiments. We are thankful to Professor K. Chattopadhyay and Professor S. Suwas (both at the Department of Materials Engineering, Indian Institute of Science, Bangalore, India) for their cooperation and discussion in the project. Support of the Networking Resource Centre for Materials (NRC-M), a scheme of University Grants Commission (UGC), India, is kindly acknowledged. One of the authors, Mr A. Gatey, would like to thank Bharat Forge Ltd for providing scholarship to do his PhD on the related topic. We would like to thank Professor S. Mali (Sinhgad Institute of Management, Kondhwa, Pune) for editing the English language in the manuscript.