Analysis of the Influence of Laser Parameters on the Microstructure and Surface Properties of Laser Deposited Aluminum Based Coatings

Abstract

The effects of processing parameters were investigated namely laser intensity and speed of laser scanning of Laser Metal Deposition (LMD) process had on the microstructure, metallurgical evolution, porosity generated in the coating, the geometrical property of the coating and the sizes of the grains in the coating. The processing parameters were applied in combinations in order to find the optimized settings of the process that least affects the metallurgical properties of the Ti-6Al-4V alloy substrate cladded with reinforced aluminium based powder. The temperature gradient and the rate of solidification of reinforcing the Ti-6Al-4V substrate with the aluminium based power were also focused on in terms of how they were influenced by the laser intensity and the scanning speed used in the building process. The inherent material properties were dependent on the process input parameters. The characterized performances considered in the investigation was influenced significantly by the laser processing intensity. The results of the investigation showed that the density had increased in proportion to the increase of the processing laser power coupled with the reduction of the speed of the laser scan. Moreover, for a laser power equivalent to and exceeding 950 W, the density became less susceptible to the laser power. The increased temperature field led to changes in geometry of the coatings as a results of more absorbed laser energy. The materials properties were influenced by the Fe-intermetallic compounds. The molten pool had columnar grains which were fully developed, along its volume as determined in the examination of the microstructure. In the direction of processing, the sample processed at 1.0-1.2 m/min had a reduction in width of the coatings from 1.643 to 1.293 mm and along the height it reduced to 0.375 at 2% Fe and 1% Mn. Increase in the percentage of both Fe and Mn increased the width of the coating to 1.833 mm at 1.0 m/min while the height continued to reduce to minimum of 0.272 mm at 1.2 m/min respectively.