Micro Wear Mechanism Of TiAlN Coated Carbide Tool In 93W Machining

Due to its excellent physical properties such as high density,high hardness,good tensile strength,high thermal conductivity,low coefficient of thermal expansion,good corrosion resistance and strong ray absorption ability,high specific gravity tungsten alloy is widely used in high-tech fields such as national defense military industry,nuclear industry and aerospace industry.In the tungsten alloy,the tungsten grains are coarse and hard,the hardness of the binder phase is low,and the bonding ability is limited.In the cutting process,brittleness removal is easy to occur,resulting in serious tool wear,which leads to short tool life,high processing cost,low efficiency,and poor surface quality.This paper takes TiAlN coated carbide tools as the research object,and studies the microscopic wear mechanism of coated tools in the cutting process of tungsten alloy.First,carry out the experiment of turning tungsten alloy with coated carbide tools under different cutting parameters.During the whole cutting experiment,the cutting force of the coated tool gradually increased with the increase of the back-grab amount and cutting stroke,and gradually decreased with the increase of the cutting speed;while the cutting temperature increased with the back-grab amount,cutting speed and cutting stroke.When the cutting stroke is 250m,the tool wear is mainly characterized by bonding wear and oxidation wear;when the cutting stroke is 1000m,the cutting edge will break The blade and the coating have a large amount of wear,and the phenomena of bonding wear,diffusion wear,oxidation wear,and abrasive wear are obvious.Based on the above research results,studies have been conducted on diffusion wear,oxidative wear and bond wear.First,in order to explore the diffusion and oxidation wear mechanism of TiAlN coated tool,a new diffusion pair bonding method was designed based on static thermal diffusion couple test.The results show that 800?is the starting temperature of coating oxidation.At 800°C and 900°C aerobic high temperature,Al₂O₃ oxide layer will be formed on the surface of TiAlN coating,which can protect the coating from further oxidation.In a vacuum environment,the diffusion of TiAlN coating and WNi Fe tungsten alloy will cause element diffusion at 800°C;In an air environment,the high-temperature oxidation resistance and the ability to hinder diffusion of the coating decrease at 800°C,element diffusion phenomenon occurs between the coating and the bonded tungsten alloy and the coating begins to be oxidized,and the oxidation and diffusion phenomenon of the coating intensify at 900?.In addition,it is found that the adhesion of tungsten alloy will hinder the formation of Al₂O₃protective layer on the surface of TiAlN coating at high temperature.Finally,the first-principles calculation method is used to study the bonding mechanism between the tungsten alloy/coating interface.The study found that WNi Fe have typical metal bonds and have certain covalent properties,and the doping of Ni and Fe elements improves the plasticity of tungsten alloys,which is beneficial to the workability of tungsten alloys.At the interface of WNi Fe/TiAlN,W atoms form covalent bonds with the main coordination atoms,and Ni and Fe atoms also form a strong bond with the atoms of the coating model.It is concluded that the covalent bond formed between the W atoms in the tungsten alloy and the TiAlN coating is the main reason for the adhesion,and the Ni and Fe binding phases enhance the adhesion of the tungsten alloy and the coating.