Wetting and Contact Interaction of Nickel Alloy with ZrB2 and (Ti, Cr)B2 Ceramic Materials.

The ZrB2–MoSi2–AlN, ZrB2–SiC–AlN, and (Ti, Cr)B2–AlN ceramic composites were wetted with a nickel-based alloy in the Ni–Cr–W–Mo system. The alloy was found to wet the ceramic composites well to form contact angles θ = 0–12° for 3–7 min on their surface. The wetting process was 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. The interaction areas were studied on cross-sections of the wetted samples. Three characteristic areas were found: refractory substrate area, transition area, and metal droplet area. The composition and microstructure of the starting ceramic material were retained by the refractory substrate area. The pores and cracks were filled with the molten alloy in the transition area at a depth up to 150 μm. There was no active chemical interaction between the metal alloy and ceramic composites, though there was insignificant diffusion (up to 3%) of some elements between the refractory substrate and the metal alloy in a thin contact area to form limited solid solutions. This was mostly observed in the wetting of materials containing SiC and MoSi2 and was manifested through the diffusion of silicon into the metal alloy. In the wetting of (Ti, Cr)B2-based materials, 1–2% of the ceramic substrate was insignificantly depleted of chromium in a narrow (3–7 μm) contact area. Despite this, the composition of the refractory substrate and the metal alloy in the interaction area was close to the starting one. In the droplet area, besides the main phase based on the NiCr solid solution, whose composition was close to that of the starting material, single inclusions of the chromium-based phase with high tungsten and molybdenum contents were found. Good wetting of the ceramic composites with the metal alloy and zero active chemical interaction between the components allow them to be jointly used for spraying coatings and making metal–ceramic composites. [ABSTRACT FROM AUTHOR]