The influence of CO2 laser and mechanical surface treatments on corrosion resistance and bacterial adhesion on biomaterials implant surface.

The object of this study is to study the effect of laser surface treatment of implant 304 stainless steel on mechanical properties surface and roughness effect on bacterial precipitate on the metal surface topography, as well as the effect of laser re-melting and mechanical (shoot peening) surface treatment of biomaterial stainless steel grades 304 implants such as hardness, microstructure, and corrosion resistance. Shot peening parameters are the angle of the nozzle of 10°, shot peening time at 15, 35, and 55 minutes with ball hardness of 55 HRC. A CO2 laser beam is utilized with parameters of 1.5, 2, and 3.5 kW power, 10.6 µm wavelengths, and a scan speed of 3 m / min with a 4 mm laser beam diameter. The laser surface re-melt process includes three stages heating, holding, and rapid cooling to modify the microstructure by phase change. The optical microscope is used to detect microstructures supported by X-Ray examination to determine the phase's transformation. Scan electron microscopy is used to study surface metallurgy after laser treatment. Surface hardening values are obtained by the Digital Vicker's Hardness test. Corrosion tests according to the standard specification of ASTM G71-31 in Ringer's Solution with specimen dimensions of (15*15*3) mm. The result shows that the shot peening due to plastic deformation produces compressive residual stresses on the surface of the metal, which effects to increases the hardness of 304 stainless steel. As the shot time increased, surface roughness increased. Also, increased bacterial precipitate on implant metal with increased smoothing surface roughness (Ra). Corrosion results ascertain that pitting corrosion is decreased with a decrease of (Icorr) for all samples after laser and mechanical surface treatment. At the same time, shot peening causes large pitting corrosion because of the rough surface than specimens after the laser process. [ABSTRACT FROM AUTHOR]