Enhanced surface composite coating on Ti811 alloy by laser cladding towards improved nano-hardness

In this study, an enhanced surface composite coating with improved nano-hardness was successfully prepared on Ti811 alloy by means of laser cladding processing. The microstructure, phase composition, interface structure, and nano-hardness of the composite coating were systematically investigated. The results show that the Ti-based cladding coating contains CrTi4, Ti2Ni, TiC, alpha-Ti, and CeCrO3. The single-track and multi-track overlapping regions of the coating form a fine metallurgical combination with the substrate and exhibit different microstructure characteristics due to differential cooling rates. The CrTi4-alpha-Ti transformation follows the Burgers orientation relationship, and the pinning effect of CeCrO3 particles distributed at the grain boundaries effectively refines the CrTi4 matrix. Moreover, the effective combination between interfaces ensures the improved nano-hardness of the coating. The results of this study provide a general guideline for studying the microstructure evolution and nanohardness of composite coatings fabricated on titanium alloys using laser cladding technology or other additive manufacturing methods.