Microstructure and wear properties of self-lubricating TiB2-TiCxNy ceramic coatings on Ti-6Al-4V alloy fabricated by laser surface alloying

摘要

To improve wear resistance of titanium alloys, TiB2-TiCxNy ceramic coatings were fabricated on Ti-6Al-4V alloy by laser surface alloying with B4C and graphite powders in nitrogen atmosphere. Microstructure and tribological properties of the coatings were analyzed. The coatings are mainly composed of in situ formed TiB2, TiCxNy and TiB2-TiCxNy epitaxial eutectic. Residual B4C and graphite exist in the uppermost zone of the coatings. Average hardness of the coatings is in the range of 1780 to 2010HV, between 3.8 and 4.4 times harder than the Ti-6Al-4V alloy substrate. The wear resistance of the coatings against Si3N4 ball is enhanced by over 14 times compared with the substrate. The coatings exhibit good wear resistance due to good anti-wear resistance of hard ceramic phases and good self-lubricating property of residual graphite. The formation mechanism of TiB2-TiCxNy epitaxial eutectic microstructure of the coatings is discussed.