Laser Surface Treatment of Cast Aluminium-Silicon Alloys

Abstract

The reason of performing the investigations carried out in this work was to investigate the microstructure of the laser treated Al-Si-Cu cast aluminium alloy with the ceramic powder particles using High Power Diode Laser (HPDL) for remelting, and/or alloying. First of all the feeding and distribution of the powder in the surface layer of the alloyed and remelted AlSi7Cu material. Very important issue is the determination of the laser treatment parameters, especially the powder feeding rate, laser power, and scan rate to achieve an enhancement of the layer hardness for ensuring this cast aluminium alloy from losing their working properties and to achieve the tool surface is more resistant to wear. The purpose of this work was also to determine technological and technical conditions comparison for the Al2O3 and SiC ceramic powder alloyed into the surface layer with High Power Diode Laser. There are presented also the investigation results about the determination of proper technical condition during the laser treatment, especially the laser head distance and shielding gas influence. The presented results concerns first of all the structure investigation of the obtained surface layer allowing it to achieve an enhanced hardness and wear resistance more resistant for work, special attention was devoted to monitoring of the layer morphology of the investigated material and on the particle occurred. Light (LM) and scanning electron microscopy (SEM) were used to characterize the microstructure of the obtained surface zones - the remelted zone (RZ) and heat affected zone (HAZ), the ceramic powder distribution and intermetallic phases occurred. A wide range of laser power values was applied and implicated with different laser scan rates. The powders in form of ceramic powders used for alloying were chosen with the particle size of ca. 60μm. This study was conducted to investigate the influence carbide and oxide powder addition on structure and mechanical properties as well the and structure changes occurred during the rapid solidification process. The investigation ensures to use laser treatment for alloying/feeding of ceramic powder particles into the surface of light alloys. The scientific reason of this work is the applying of High Power Diode Laser (HPDL) for improvement of aluminium`s mechanical properties, especially the surface hardness. As the main findings was determined that the obtained surface layer is homogeny without cracks and has a comparably higher hardness value compared to non-treated material. The surface hardness increases together with the applied laser power, the highest power applied gives the highest hardness value for the surface. Also the distribution of the ceramic particles is proper, but there a need for further modelling, because the hardness increases in general according to the laser power used so that the highest power applied gives to highest hardness value in the remelted layer, but for other powder amount or alloy the values should be determined separately, and more data would be necessary to create a model for the technique appliance. The practical purpose of this work is to analysis the impact and application possibility of HPDL laser surface treatment on the cast Al-Si-Cu alloys to deliver application possibilities for diverse branches of industry.