激光熔覆原位TiC/Fe复合涂层增强相形成机制研究

激光熔覆技术在制备原位自生颗粒增强金属基耐磨复合涂层领域具有良好的应用前景。以廉价钛铁和石墨为熔覆粉末,采用横流CO2激光器在低碳钢基体上制备了TiC增强Fe基复合涂层,并对涂层物相组织和TiC增强相的形成机制进行了研究。结果表明,增强相TiC通过原位冶金反应形成,在熔体的冷却过程中析出长大,具有树枝晶和鱼骨状两种形态。树枝晶形态的TiC为熔体先析出相,其生长形态受界面前沿成分过冷和晶体生长习性控制。鱼骨状TiC由δ-Fe和TiC的准共晶反应形成,溶质原子扩散特征和晶面能决定了共晶TiC的最终鱼骨状形貌。均匀弥散分布的TiC增强相有助于提高涂层的耐磨损性能。

Formation Mechanism of Reinforcement in Laser Clad in Situ TiC/Fe Composite Coating

Laser cladding is a promising technique in the field of fabricating in situ particulate reinforced metal matrix anti-wear composite coating.The cheap ferrotitanium and graphite was used as clad powder to produce TiC reinforced Fe-based composite coating on low carbon steel by transverse-flow CO2 laser equipment.Phase constituents,microstructure and formation mechanism of TiC in the coating were investigated.Results show that TiC is formed through the in situ metallurgical reaction.TiC with dendritic and fishbone-like morphology precipitate and grow during the cooling process.Dendritic TiC is the primary phase formed in the melt and its morphology is controlled by the constituent supercooling at the interface and growth habit of the crystal.Fishbone-like TiC is formed as a result of the quasi-eutectic reaction of δ-Fe and TiC.Diffusion characteristic of the solutes and interface energy determines the fishbone-like morphology of the eutectic TiC.Finaly dispersed TiC reinforcement in the composite coating is beneficial to the improvement of wear resistance of the coating.