Abstract
Surface engineering applications has brought titanium and its alloys into limelight in the manufacturing industries such as the aerospace, automobile, marine, food processing and chemical processing industry. Despite the growths experienced in the use of this material, Ti and its alloys are plagued with poor wear behaviour especially when in contact with other materials during application. This limitation of Ti-based components has led to a search for techniques and processes to modify, restructure and re-engineer such materials for extended lifespan and for reuse. Among various techniques for restoring and protecting the material is by the use of the laser metal deposition (LMD) technique otherwise called the laser cladding process. The LMD is a technique used to achieve a coating on components which allow the addition of reinforcing particles to improve the surface properties of titanium-based materials. These properties include hardness, wear amongst others.
This research study involves the use of the LMD process to deposit composites coatings on titanium alloy (Ti6Al4V) substrate using Rofin Sinar 3.0 KW Ytterbium fibre laser system. The reinforcement titanium alloy (Ti6Al4V) and boron carbide (B4C) ceramic powder were employed to deposit Ti6Al4V-B4C composites coatings on Ti6Al4V substrate. The microstructural evaluation, geometrical analysis, porosity analysis, microhardness profiling and the wear characteristics of laser cladded composites were investigated. Samples from the as-deposited laser cladded composites were characterized using optical microscopy (OM), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) and x-ray diffraction (XRD). Both geometrical and porosity analyses were carried out to investigate the rate of dilution and defects such as porosity and cracks on the deposited composites coatings. Furthermore, performance characteristics were investigated using microhardness tester and CETRUMT-2 tribometer for the wear test analysis of the laser clad coatings of Ti6Al4V-B4C composites.
This research work is also aimed to establish process parameters that will result in defect-free composite coatings. The microstructure of the Ti6Al4V-B4C composites revealed a pore and crack free clad when observed at laser power of 2200 W. The SEM analysis revealed that there is uniform distribution of the ceramic particles in the titanium matrix at higher laser power. The geometrical analysis of the samples revealed that the aspect ratio (AR) and the dilution (D) increases with an increase in the laser power. The results obtained further revealed the dilution of approximately between 34% and 46% with aspect ratio between 2.16 and 3.58 were the best in terms of defectology for the combined with acceptable geometrical characteristics. The EDS and the XRD results revealed that there is a relationship between intermetallic phase of α+β titanium alloy and boron carbide in which certain amount of peaks...
M.Ing. (Mechanical Engineering)