Adhesion and diffusion mechanisms of the cBN tools in the high-speed cutting of nickel-based superalloys

Nickel-based superalloys have attracted much more attention in the aerospace industry due to their exceptional properties of high-temperature strength and thermal stability. However, the high-speed cutting of nickel-based superalloy is accompanied by strong coupling effects of thermal-mechanical loads due to low thermal conductivity and high strength , which in turn leads to severe adhesion and diffusion wear for cutting tools. Unfortunately, the underlying mechanisms of adhesion and diffusion for cubic boron nitride (cBN) tools in the high-speed cutting of nickel-based superalloys are still unclear. To address this issue, this work mainly aims to reveal the adhesion and diffusion mechanisms by qualitative and quantitative characterizations involving nanoindentation , scanning electron microscopy (SEM), transmission electron microscopy (TEM) and transmission kikuchi diffraction (TKD) at micro/nano scales. The average hardness of cBN tools at the cutting edge interface is about 27–32 GPa. The thickness of adhesive layers of cBN tools is about 20–60 μm in the high-speed cutting superalloys. The thickness of reaction layers is about 28–65 nm at the diffusion interface between cBN and nickel-based superalloys. The reaction products at the diffusion interface are Ni 23 B 6 , Ni 2 B, Ni 3 B, (Cr 2 Ni 3 )B 6 and (Cr 3 Ni)B 6 . The dislocation of cBN grains is quantitatively determined to be ∼70 × 10 14 /m 2 . The formation of reaction layers at the interface between optimized cBN and nickel-based superalloys acts as a tool protective layer and diffusion barrier effects, which further prolongs the tool life.