硬质合金覆层-钢基体结合界面层及其生长模型的研究

采用液相烧结技术制备的三元硼化物硬质合金覆层材料具有成本低廉、耐磨抗蚀的优异性能。利用覆层连结试样和抗弯强度法测定的覆层材料的覆层-钢基体界面结合强度为740MPa。覆层与钢基体之间的断裂破坏不是由于覆层与钢基体之间结合界面的剥离,而是发生于界面附近的钢基体和覆层内。利用显微硬度计测定了覆层-钢基体界面结合区的显微硬度变化,并利用SEM-EDS研究了覆层-钢基体界面微观结构和界面区元素分布。在覆层-钢基体结合界面处,存在由高硬度(覆层)到低硬度(钢基体)的狭窄过渡区,合金元素浓度分布没有突变,形成一个具有一定厚度的过渡层。分析了覆层-钢基体界面层形成的机理,并以扩散理论为基础,建立了覆层材料覆层-钢基体界面层生长的数学模型。

STUDY ON BOND INTERFACE OF HARD ALLOY CLAD-STEEL SUBSTRATE AND THE MODEL OF INTERFACE LAYER

Using liquid phase sintering technique, ternary boride cermet clad material was prepared, and have good properties as lower cost, high wear resistance, high corrosion resistance. The bond strength between the cladding and the steel substrate of clad material are measured using three-point bending method, and the measured values is 740.38MPa. The measured results indicate that a strong bond interface exists between the cladding and the steel substrate. Fracture does not occur at the bond interface, but initiates in the interior of the steel substrate or the cladding in the vicinity of the interface. The micro hardness, microstructure and element distribution in the vicinity of the bond interface are investigated. It is shown that the cermet cladding has high microhardness. In the vicinity of the bonding interface, there exists a narrow transitional zone, in which the distribution of elements Mo and Fe continuously changes. No clear bonding interface exists between cladding and steel substrate, but a transitional layer with a certain thickness is formed, and become a firm metallurgical bond between cladding and steel substrate. The formation mechanism of the interface between the cladding and the steel is investigated. A mathematical model about the growth of interface layer is established according to the theory of diffusion. It is shown that the thickness of bonding layer is mainly related to the sintering temperature and the holding time.