Micromilling of titanium alloys : a comparison between workpieces produced by casting, ECAP and 3D printing (SLM)

Abstract

Properties like good corrosion resistance and biocompatibility as well as satisfactory mechanical resistance make titanium and its alloys a good candidate for applications in biomedical industry. Commercially pure titanium (CP-Ti) is the ideal titanium-based material to use in the manufacturing of dental implants as alloying elements can decrease its biocompatibility. However, CP-Ti shows limited mechanical properties for a few implant applications. Ti-6Al-4V is the most common titanium alloy used in biomedical implants. Machining is one of the main manufacturing process involved in producing implants and micromilling is one of the process that can be used. The proposition of this thesis is to analyze and compare the micromilling machinability of four different titanium-based materials, indicating the better suited material regarding this manufacturing process among: standard commercially pure titanium grade 2, standard Ti-6Al-4V alloy, CP-Ti processed by equal channel angular pressing (ECAP) and Ti-6Al-4V fabricated by selective laser melting (SLM). Machinability was analyzed considering cutting forces, surface roughness, burr formation, microchips morphology as well as their mechanical properties and their influence in each factor was analyzed. It was designed a series of experiments varying feed per tooth and covering a wide range, from 0.5 to 4.0 µm, so a possible ploughing behavior could be identified. Despite presenting higher strength and hardness, SLM material presented the best machinability among the materials. It presented lower surface roughness, burr formation, a good microchip morphology and the cutting force was only higher than for CP-Ti, which has the worst mechanical properties values.