In-situ TiB reinforced titanium matrix composite coatings prepared by laser cladding: Effect of TiB2 content on microstructure, hardness and wear properties

To enhance the wear resistance of the Ti6Al4V alloy surfaces, four TiB-reinforced titanium matrix composite (TMC) coatings were in-situ synthesized via laser cladding. This study systematically explored the effects of varying TiB2 contents (5, 15, 25 and 35 wt%) on the microstructure, hardness and wear resistance of the coatings. The results revealed that all TMC coatings contained in-situ synthesized TiB reinforcements, residual TiB2, alpha-Ti matrix and small amounts of beta-Ti. The addition of 5 wt% TiB2 (hypoeutectic region) formed fine eutectic TiB whiskers (TiBw) as reinforcements. At higher TiB2 contents (hypereutectic region), hollow columnar primary TiB and eutectic TiBw were formed. The hardness of the TMC coatings exceeded that of the Ti6Al4V substrate and increased with increasing TiB2 content. Nanoindentation tests indicated that the residual TiB2 and primary TiB had higher hardness and elastic modulus than eutectic TiBw and Ti matrix. The wear resistance of the four TMC coatings was 3-4 times greater than that of the Ti6Al4V substrate, and samples with higher TiB2 additions are more wear resistant. Abrasive wear was identified as the dominant wear mechanism and the improved wear resistance can be attributed to the reinforcing effects of residual TiB2 and primary TiB.