Boronization of titanium alloy

Abstract

The study focused on investigating the pack-boronizing of Ti-alloy using a novel experimental setup, where boronization was conducted at 1100°C for 25 h. The choice of the experimental setup was found to significantly influence the outcome of the boronization process, emphasising the importance of selecting the appropriate setup to achieve desired results. The following three types of experimental setups were studied for the boronizing process: (i) Setup 1 involved the conventional approach of pack-boronization (which is typically used for boronization of steels). (ii) In setup 2, aluminium was mixed along with the boronizing mixture (to tackle the problem of oxidation of Ti-alloy in the open atmosphere muffle furnace). (iii) In setup 3, a slight change in experimental setup 2 was made, where, instead of mixing aluminium with the boronizing mixture, the layer of aluminium powder was stacked above and below the boronizing mixture. Setup 1 formed TiB, but TiB2 formation was not observed. Notably, setup 3 demonstrated favourable outcomes, as supported by SEM micrographs, EDS, and XRD analysis, which confirmed the presence of a uniform TiB2 phase on the Ti-alloy surface after boronization under the specified conditions. An outstanding benefit of the boronization process was the remarkable improvement in surface hardness. The borided sample exhibited a maximum hardness of 3000 HV0.1, representing approximately nine times the hardness of the non-boronized Ti-alloy, which only reached 340 HV0.1. This substantial increase in hardness renders the boronized material highly desirable for applications that necessitate enhanced microhardness and wear resistance, including biomedical implants and industrial components subject to tribological stress. Moreover, the designing of the experimental setup was crucial to tackle the issue of delamination of the boride layer. Setup 2 was helpful in obtaining TiB2 layer, but delamination of the layer was an issue.