Research On The Cutting Property Of PCBN Tools In Turning Nickel-Based Superalloy

The nickel-based superalloy GH4169 is widely used in the aerospace industry because of its excellent comprehensive mechanical properties under high temperature and corrosion condition. It is one of the most difficult-to-machine materials due to low thermal conductivity and hard particle.One of the methods solving the problem of machining difficult-to-machine materials is using new material cutting tool. PCBN tool has excellent cutting property in machining nickel-based superalloy because of its great hardness, high wear resistance and good chemical stability. This paper studies the cutting property of PCBN tools in turning nickel-based superalloy GH4169 under different edge geometry parameters, cutting speeds, cutting environment and PCBN component, discusses the wear form and mechanism and studies the side flow of the chip and its influence.According to the results of turning nickel-based superalloy GH4169 with PCBN tools, the tool wear decreases when tool nose radius and negative chamfer angle are large or negative chamfer width is small, the tool wear increases when cutting speed is high, the cutting property of DBW85 tool is better than that of BZN6000 and BTN100 tools, the DBW85 tool's wear is even smaller at high cutting speed than the other two kinds of material at low cutting speed. It is observed that wet cutting can reduce tool wear by 40%～50% than dry cutting; the flank wear of BZN6000 and BTN100 tools are irregular while DBW85 tool's wear is uniform, the rake face has crater wear and generates the deep groove at the contact region with the chip edge; turning nickel-based superalloy GH4169 will easily cause the side flow of chip which generates the sawtooth at the side face; the major wear mechanisms are adhesive and diffusion wear, oxygenation and phase transition wear, micro-breakout and mechanical wear. When the cutting speed increases, the softening material due to the high temperature will make the cutting forces reduce, at the same time the increased tool wear will make the cutting forces increase, they influence the cutting forces together; and the cutting forces will increase when the cutting depth and the feed rate increase. From the above experiment results, it is considered that the W element in the binders will increase the fracture toughness and inoxidizability of PCBN tool while Co and Al elements can improve the stability of the tool, so the W-Co-Al based DBW85 tool shows better cutting property; BZN6000 tool only uses Co element as the binder which will diffuse with the Ni element under high temperature and lead to diffusion wear, so its cutting property is not as good as DBW85 tool; the oversize CBN particle of BTN100 tool reduces the sintering strength and the crack extension resistance, therefore, the cutting property of BTN100 tool is worse than that of DBW85 and BZN6000 tools.