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

Abstract

A 1.5 kW CO 2 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 90 m laser beam spot size focused onto the surface was used to provide high irradiances (up to 23.56MW/cm 2 ) with low residence times (as low as 50 s) 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.

Influence of pre-heating on the surface modification of powder-metallurgy processed cold-work tool steel during laser surface melting

“…5a and 6a, when a pre-heating at 200 • C was performed, a higher solidification rate was reflected in a finer structure. These results are consistent with the relevant scientific literature [20,[29][30][31]. The pre-heating at 350 • C ensures a smaller temperature difference between the remelted steel surface and the bulk of the material than in the case of pre-heating at 200 • C or without any pre-heating.…”

“…Consequently, the mechanical properties of tool steels may be controlled. Optimizing process parameters of laser surface treatments to achieve better properties of various steels remains a relevant topic [12][13][14][15][16][17][18][19][20][21]. The most important laser processes are as follows: laser heat treatment, laser melting, laser cladding and laser alloying [22].…”

Microstructural aspects of laser surface treatment of commercially pure titanium

“…The laser modification is generally carried out using Nd:YAG lasers [6,7] or CO 2 lasers [8,9]. Laser surface treatment is one of the most innovative and effective methods of surface treatment of a wide range of engineering materials [10][11][12][13][14][15]. The application of a laser beam causes the microstructure of the treated material to be formed in the conditions of a high-temperature gradient and a very short process duration.…”

Laser Polishing of Additive Manufactured 316L Stainless Steel Synthesized by Selective Laser Melting

“…Laser polishing offers flexibility in producing bespoke high levels of surface polishing, as well as high dimensional accuracy. Several researchers have investigated the most significant processing parameters on the final roughness and the resulting chemical and mechanical properties for different metals and metal alloys [23,24,25,26,27,28,29,30,31]. These parameters include the laser beam power, the scanning speed, the laser beam focal position, and the number of scanning passes.…”