Effects of substrate heating on the microstructure and hardness of TiB/Ti6Al4V-ELI during laser in-situ metal deposition

This work investigated the influence of heating temperature (°C) on the microstructure and microhardness of TiB/Ti6Al4V-ELI composite clads that were produced via in-situ alloying using laser metal deposition technique. The samples were produced on a Ti6Al4V base plates which were heated at different temperatures (25°C, 200°C, 300°C, 400°C and 500°C) before they were characterised for microstructure and hardness. It was found that the TiB/Ti6Al4V-ELI sample that was produced on a non-pre-heated base plate was characterized by TiB particles and had the lowest hardness of 511 ± 66 HV. Base plate heating resulted in the formation of TiB whiskers that were dispersed within the titanium matrix. 200°C led to a microstructure with clusters of TiB whiskers hence it had an increased hardness of 651 ± 40 HV. A fine microstructure with homogeneous distribution of the TiB whiskers was obtained at 500°C base plate heating temperature and had hardness of 565 ± 14 HV.