Abstract
Metal matrix ceramic composites (MMCs) are widely applied materials in surface engineering due to their high hardness and excellent wear resistance. Recently, various MMCs have been successfully fabricated by a promising method named direct laser deposition. In this work, nickel-based hard surface coatings reinforced with multiple in-situ phases were deposited by wide-band laser. The strengthened phases were synthesized by varied content of Ti and B4C precursor powders. The microstructure evolution, phase constitution and mechanical properties of the designed coatings were investigated. Results indicated the B4C were decomposed and free C and B atoms were released in a molten pool. Multiple secondary phases such as TiC, Cr7C3, Cr23C6, TiB and CrB were in-situ synthesized. As the content of precursor Ti and B4C powders increased, the microstructure of the laser-clad coatings was greatly refined due to the plentiful in-situ phases. Mechanical properties of the coatings revealed the maximum elastic modulus and microhardness reached 247 and 7.18 GPa in the experiment group. Friction tests indicated the average friction coefficient of optimized coating was about 0.50.
Highlights
Metal matrix ceramic composites (MMCs) have been one of the most important surface hardening materials in engineering [1,2,3]
This research aims to explain the essential relationship between the microstructure evolution, phase constitution and mechanical properties of coatings deposited by wide-band laser
Nickel coatings reinforced with multiple in-situ phases were deposited by wide-band laser
Summary
Metal matrix ceramic composites (MMCs) have been one of the most important surface hardening materials in engineering [1,2,3]. MMCs are mainly composed of a metal matrix which act as the binder phase and hard ceramic particles which are the strengthening phases [4,5]. Various MMC coatings have been successfully applied to modify the surface performances of engineering steels such as the hardness, wear resistance, corrosion resistance, oxidation resistance, etc. Former researchers have proved that the in-situ-synthesized ceramic particles have advantages of homogeneous distribution, high density, dense bonding and flexible design [9,10,11]. Verdi et al deposited a MMC Inconel625-Cr3C2 coating by laser cladding onto ferritic steel [13]. The in-situ-formed Cr7C3 carbides dramatically improved the hardness of the coatings
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