Boronization and characterization of Ti6Al4V alloy used as a biomaterial

In this present study, Ti6Al4V alloy, was pack boronized at 950, 1050, 1150 ºC and 5, 10, 15 hours using four different boronizing mixtures in atmospheric environment. After the boriding process, TiB2 and TiB layers with low density, high hardness, high wear and corrosion resistance were formed in the near-surface area. The hardness and depth of the formed TiB2 and TiB layers were measured. After boronization, optical microscope, XRD, SEM, EDX analysis and microhardness measurement studies were carried out and boriding kinetics were calculated. Obtained results were compared. When the optical microscope images of the samples boronized with the mixture 1 are examined, the lowest TiB2 layer thickness is 1,66 µm in the samples boronized at 950 °C for 5 hours, and the highest layer thickness is 13,91 µm in the samples boronized at 1150 ºC for 15 hours. When the optical microscope images of the samples boronized with the mixture 2 are examined, the lowest TiB2 layer thickness is 4,15 µm in the samples boronized at 1050 °C for 5 hours, and the highest layer thickness is 7,42 µm in the samples boronized at 1150 ºC for 15 hours. When the optical microscope images of the samples boronized with the mixture 3 are examined, the lowest TiB2 layer thickness is 1,22 µm in the samples boronized at 950 °C for 5 hours, and the highest layer thickness is 13,39 µm in the samples boronized at 1150 ºC for 15 hours. When the optical microscope images of the samples boronized with the mixture 4 are examined, the lowest TiB2 layer thickness is 5,01 µm in the samples boronized at 1050 °C for 5 hours, and the highest layer thickness is 9,27 µm in the samples boronized at 1150 ºC for 15 hours. When the boriding mixtures are compared in terms of the TiB2 layer thickness they form, the samples made with the mixture 1 borided with the mixture 1 gave the best results. When the XRD patterns taken from the samples boronized with the 1, 2, 3 and 4 mixture were examined, it was observed that the peak intensities of TiB2 and TiB and increased with the increase in temperature and time. Boronizing mixtures were compared in terms of the highest hardness value reached, the mixture 1 gave the best result with a value of 27.51 GPa. The SEM images taken from the samples are examined, TiB2 and needle-like TiB layers were seen on the surface. Diffusion coefficients (K) were calculated with the help of the slopes of the graphs drawn between the square of the TiB2 layer thicknesses obtained from the samples boronized with the mixture 1 and the boriding time. With the slopes of the graphs drawn between the obtained diffusion coefficients and boriding temperatures, the boriding activation energy was calculated as 233532.88 J/mol. The boriding activation energy for the samples boronized with the mixture 3 was calculated as 235423,62 J/mol. When evaluated in terms of boriding kinetics, it is seen that the mixture 1 gives a lower activation value.