Complex analysis of elaboration of steel–TiC composites by direct metal deposition

摘要

Development of composites with multifunctional properties is a challenging problem that could be solved by laser cladding. Robotic laser cladding with coaxial powder injection is often referred to as direct metal deposition (DMD). The objective of the present work is to demonstrate the advantages of the optical monitoring in optimizing the deposition of carbide-reinforced metal matrix composites (MMCs). A multiwavelength pyrometer and an infrared camera are applied to analyse high temperature heat and mass transfer in the DMD zone. The influence of the laser power, laser cladding speed, and powder feeding rate on the true temperature is studied. The thermal images of the molten pool obtained by the infrared camera for different TiC contents in the powder blend are analysed as well as the beads geometry, microstructure, and microhardness. It is found that MMC with the low TiC content (2.5 and 5 vol. %) has the highest microhardness (about 550 HV0.1) due to the formation of the supersaturated solid solution of TiC in α-Fe with a strong distortion of the crystal lattice. At the 10 vol. % TiC content, the material microhardness insignificantly exceeds the one of the pure laser-cladded steel (about 280 HV0.1) because of the nonequilibrium eutectic which is composed mainly of the ductile α-phase in the form of a rim around the TiCprim crystals.