Abstract
Titanium and its alloys are regarded as super alloys because of their ability to maintain high strength and light weight properties at elevated temperatures. Titanium has posed problems during its machining; as it always reacts with the machining tool at high temperatures, making it one of the most expensive metals to machine. It has been the interest of researchers to be able to use additive manufacturing methods in the fabrication of titanium; and the rise in the use of the Laser Metal Deposition process in the manufacturing of titanium has led to research studies in additive manufacturing. However, complex interrelationships exists between the processing parameters which lay a demand to optimise the parameters. There has also been a rise in the demand for the bone implants recently in the biomedical industry. The main implants on demand are the dental, knee and hip implants. However, the biocompatibility of the existing materials has been an issue for some time; as most of these materials become reactive in the body for long-term implantation. This has led to the development of titanium as a material for bioimplants.
This research study presents a platform for analysing the laser power interaction effects on the evolving properties of commercially pure titanium during laser metal deposition tailored for biomedical applications. A set of preliminary studies was first conducted to establish the processing parameter window. A total of seven samples were fabricated by depositing titanium powder onto a Ti-6Al-4V base metal by varying the laser power from 400 to 1600 watts, whilst keeping all the other parameters constant. This was done to check how the laser power relates to the material properties of titanium; as the laser power is recognised as one of the most influential parameters on the evolving properties of laser deposited materials. The microhardness, microstructure, wear resistance and bio-compatibility tests were conducted for the material characterisation of this study. The optimized processing parameters obtained for this research study were: the spot size of 4 mm, powder flow rate of 2 rpm, gas flow rate of 2 l/min, and the scanning speed set at 0.002m/s.
The microstructural evaluation revealed that the rate of dilution increased with an increase in the laser power. The increase in the dilution ratio tended to have negative effects on the wear resistance capabilities of the deposited materials. As the dilution increased, the wear resistance of the deposits decreased. This is attributed to the fact that the bond strength of the deposits decreases with an increase in the laser power. Also, the microstructural evaluation showed that finer martensitic...
M.Ing. (Mechanical Engineering)