Abstract
In this paper, a TiC reinforcement metal matrix composite coating is produced using nickel and graphite mixing powder on the surface ofTi-6Al-4V alloy by laser radiation. The microstructure of the coatings is investigated by XRD, SEM and EDS. Results show that most of the TiC phase is granular, with a size of several micrometers, and a few of the TiC phases are petals or flakes. At the cross-section of the coatings, a few special TiC patterns are found and these TiC patterns do not always occur at the observed cross-section. The even distribution of the TiC phase in the coatings confirms that the convection of the laser-melted pool leads to the homogenization of titanium atoms from the molten substrate, and carbon atoms from the preplace powder layer, by the mass transfer. The characteristics of the TiC pattern confirm that the morphology and distribution of the primary TiC phase could be influenced by convection. Two main reasons for this are that the density of the TiC phase is lower than the liquid melt, and that the primary TiC phase precipitates from the pool with a high convection speed at high temperature.
Highlights
In situ metal matrix composite (MMC) coatings involve the reinforcement phases being synthesized in a metallic matrix which might be molten by chemical reactions between elements, or between the element and compound, during the coatings process
A TiC-reinforced Ni-based composite coating was produced on the surface of Ti-6Al-4V alloy when the nickel and graphite mixing powder layer was radiated by a laser beam
Some TiC particles formed a number of special TiC patterns; this did not always occur in the observed cross-sections
Summary
In situ metal matrix composite (MMC) coatings involve the reinforcement phases being synthesized in a metallic matrix which might be molten by chemical reactions between elements, or between the element and compound, during the coatings process. Due to the properties of metal matrix composite coatings, the selectivity of the manufacturing process mainly focuses on various high-energy beam technologies, such as welding arc [4], plasma arc [5], electron beam [6] and laser beam [7]. The manufacturing process has had an important influence on the size and distribution of the reinforcement and the properties of MMC coatings. Among different MMCs coatings, TiC reinforcement coatings have shown great potential for metal surface strengthening applications because of appropriate properties such as high hardness and high melting point, as well as excellent thermal and chemical stability. Among different MMCs coatings, TiC reinforcement coatings have shown great potential for metal applications because of appropriate properties such as high hardness.
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