WETTING AND CONTACT INTERACTION of NICKEL ALLOY WITH ZrB₂ AND (Ti, Cr)B₂ CERAMIC MATERIALS

Abstract

The ZrB₂–MoSi₂–AlN, ZrB₂–SiС–AlN, and (Ti, Cr)B₂–AlN ceramic composites were wetted with a nickel-base alloy in the Ni–Cr–W–Мо system. The alloy was found to wet the ceramic materials well to form contact angles θ = 0–12° for 3–7 min on their surfaces. The wetting process is less influenced by the composition of the main phase (ZrB₂ and (Ti, Cr)B₂) and greater by the content of SiC and AlN dielectric additions, impairing the wetting of the composites. Interaction areas were studied on cross-sections of the wetted samples. Three characteristic zones were revealed: a refractory substrate, a transition zone, and a metal droplet. The composition and microstructure of the starting ceramic material are retained in the refractory substrate area. In the transition are at a distance of up to 150 μm, the pores and cracks are filled with the molten alloy. There is no active chemical interaction between the components of the metal alloy and ceramic composites, though insignificant diffusion (up to 3%) of some elements of the refractory substrate into the metal alloy and vice versa occurs in a thin contact area to form limited solid solutions. This is mostly observed in the wetting of materials containing SiC and MoSi₂ and is manifested through the diffusion of silicon into the metal alloy. In the wetting of (Ti, Cr)B₂-based materials, insignificant depletion (1–2%) of the ceramic substrate of chromium is observed in a narrow (3–7 μm) contact area. Despite this, the composition of the refractory substrate and the metal alloy in the interaction area is close to the starting one. In the droplet area, besides the main phase based on the NiCr solid solution, whose composition is close to that of the starting material, single inclusions of the chromium-based phase with a high content of tungsten and molybdenum were found. In general, good wetting of the ceramic composites with the metal alloy and the lack of active chemical interaction between the components of the materials allow them to be commonly used for spraying coatings and making metal–ceramic composites.