Optimization of Laser and Electrochemical Process Parameters for Surface Modification of Hardness and Hydrophobicity on 316L Steel
R. Thanigaivelan, R.M. Arunachalam, A. Nithish, S. Venkatesh, P. Naveenkumar, S. Selvaganapathy and A.R. Siranjeevi Aravind
Stainless steel is used in variety of applications because of its good mechanical properties and composition. A 316L stainless steel was used as a specimen to study the effect of a fibre laser dimpled and electrochemically treated surface on output characteristics such as surface roughness, hardness and contact angle. A L9 orthogonal array experiments are designed on factors and levels. The dimple distance, laser power, inter-electrode gap (IEG) voltage and electrolyte concentration were considered as factors that affect the output performances such as surface roughness, hardness and contact angle. The 316L stainless steel was dimpled using a fibre laser beam and electrochemically treated for an hour to modify the surface properties. The technique for order of preference by similarity to ideal solution TOPSIS) was used to identify the best solution and, based on the TOPSIS analyse, the optimal combination of lowest dimple distance of 150, laser power of 14 W, supply electrode voltage of 4 V and electrolyte concentration of 10 g/l of NaNO3 results in a surface roughness value of 2.64 μm before electrochemical treatment and 1.08 μm after electrochemical treatment, surface hardness of 538.21 N/mm2 and contact angle of 111.1º. In general, high surface roughness is good for tissue interlocking and moderate surface quality is suitable for bone/implant interface areas; hence this study proposes the optimal surface quality of osteosynthesis plate for better application. Based on analysis of variance (ANOVA) the laser dimple distance plays a significant role on output performances. Additionally, the laser power and IEG voltage shows the notable effect on output characteristics whose percentage contribution is more than 10%.
Keywords: Fibre laser, 316L stainless steel, dimple, laser surface engineering, electrochemical treatment, contact angle, osteosynthesis plate, technique for order of preference by similarity to ideal solution (TOPSIS), analysis of variance (ANOVA)