Microstructural evolution and high-temperature oxidation of TiC/IN625 coatings fabricated by multi-layer extreme high-speed laser cladding.

• Pores- and cracks-free TiC/IN625 coatings over AISI 1045 steel were firstly prepared by EHLA. • EHLA TiC/IN625 coatings possessed much more uniform and finer microstructure. • High resistance is attributed to lower surface roughness, smaller dendrite size, smaller grain size, and higher amount of LAGBs. The multi-layer TiC/IN625 coatings were deposited on AISI 1045 steel substrate by conventional laser cladding (CLA) and extreme high-speed laser cladding (EHLA). The surface morphology, microstructure and high-temperature oxidation resistance of the TiC/IN625 coatings were characterized and compared. The results showed that the cladding speed has a significant effect on surface quality. Within the range of the set parameters, the best surface quality is obtained when the cladding speed is 49.8 m/min, where Ra is 11.75 μm and Sa is 13.17 μm. The microstructure of the TiC/IN625 coatings is dominated by dendrites. Smaller dendrites arm spacing and no apparent transition layer are found at the layer-to-layer interface in the EHLA sample. A two-layered oxide structure is formed in the cross-section of all samples. The EHLA sample exhibits a lower mass loss compared to the CLA sample, indicating that EHLA sample can withstand high-temperature oxidation. The improvement of high-temperature oxidation resistance is mainly attributed to the lower surface roughness, smaller dendrite size, smaller grain size, and higher amount of LAGBs. [ABSTRACT FROM AUTHOR]