Spinodal decomposition in AISI 316L stainless steel via high-speed laser remelting

• Published in: Applied surface science 2014-05, Vol.302, p.318-321
• Main Authors: Chikarakara, Evans, Naher, Sumsun, Brabazon, Dermot
• Format: Article
• Language: English
• Subjects: 316L stainless steel; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Lamellar and nodular structures; Laser remelting; Physics; Spinodal decomposition
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2013.10.099

•Extremely high cooling rates achieved via high-speed laser remelting of 316L stainless steel using high irradiances and low residence times.•Formation of unique nodular structures due to high temperature and cooling rate spinodal decomposition.•Elimination of cracks, inclusions and voids within the laser treated region.•Grain structure reorientation between the bulk alloy and laser-treated region due to the high thermal gradients resulting from laser process.•Laser remelting showed a high degree of repeatability and homogeneity. A 1.5kW CO2 pulsed laser was used to melt the surface of AISI 316L stainless steel with a view to enhancing the surface properties for engineering applications. A 90μm laser beam spot size focused onto the surface was used to provide high irradiances (up to 23.56MW/cm2) with low residence times (as low as 50μs) in order to induce rapid surface melting and solidification. Variations in microstructure at different points within the laser treated region were investigated. From this processing refined lamellar and nodular microstructures were produced. These sets of unique microstructures were produced within the remelted region when the highest energy densities were selected in conjunction with the lowest residence times. The transformation from the typical austenitic structure to much finer unique lamellar and nodular structures was attributed to the high thermal gradients achieved using these selected laser processing parameters. These structures resulted in unique characteristics including elimination of cracks and a reduction of inclusions within the treated region. Grain structure reorientation between the bulk alloy and laser-treated region occurred due to the induced thermal gradients. This present article reports on microstructure forms resulting from the high-speed laser surface remelting and corresponding underlying kinetics.