Research On Dry Cutting Performance And Wear Mechanism Of TiCN,TiAlN And TiAlCrN Coated Tools

As a kind of an economical and effective way,ceramic coatings can be improved the overall performance of materials.It not only has the characteristics of high hardness,good wear resistance,high bonding strength and low thermal expansion coefficient at room temperature,but also has high strength at high temperatures,excellent corrosion resistance,wear resistance and high temperature oxidation resistance.Ceramic coatings can be deposited on the surface of cemented carbide cutting tools to effectively improve the hardness,abrasion resistance,oxidation resistance and service life of the substrate.The significance of the coated tools is combined the characteristics of the tool material with the superhard coating to realize the comprehensive modification of the traditional tool and meet the needs of modern metal cutting technology.In this paper,TiCN,TiAlN and TiAlCrN coatings were deposited on the specimens' of W12Mo3Cr4V3 N steels and cemented carbide cutting tools by PVD technology.And the following experiments have been carried out in current work:(1)Micro-hardness and adhesion strength of TiCN,TiAlN,and TiAlCrN coatings were measured by a micro-hardness tester and a scratch tester.(2)The reciprocating sliding tests of TiCN,TiAlN and TiAlCrN coatings on the surfaces of W12Mo3Cr4V3 N steels have been performed to investigate the friction coefficients of coatings affected by various normal loads,reciprocating speed and temperature conditions.The wear morphologies and mechanism had been also analyzed under corresponding tests conditions.(3)Uncoated tools,TiCN,TiAlN and TiAlCrN coated tools were used to perform dry cutting tests on 20 CrMo steel.The influences of cutting parameters on cutting force,cutting temperature and workpiece surface roughness had been studied.(4)The dry turning processes of coated tools were simulated with Deform-2D software.The distributions and changes of the stress filed,temperature field and cutting forces were obtained.(5)The wear amount VB of flank surfaces was measured by optical microscope.Micro-morphologies in the worn zone of TiCN,TiAlN and TiAlCrN coated tools after cutting tests were observed using scanning electron microscope(SEM).The wear form and mechanism of coated cutting tools were explored in this study.Based on the theoretical and experimental analysis,main conclusions are drawn as follows:(1)The micro-hardness and adhesion strength of the three coatings are all relatively large.The micro-hardness is arranged in order of TiAlCrN coating> TiAlN coating> TiCN coating> uncoated specimen;the binding force is arranged in order of TiCN Coating> TiAlCrN Coating> TiAlN Coating.The test results of the friction coefficients show that the friction coefficient of TiAlN coating is the largest under changing load,reciprocating speed and temperature,followed by TiAlCrN coating and the TiCN coating is smallest.The main wear patterns of TiCN coatings are fatigue wear and oxidation wear,the TiAlN coatings are abrasive wear and oxidation wear,and the TiAlCrN coatings are fatigue wear and abrasive wear.(2)TiCN,TiAlN,and TiAlCrN coatings improve the cutting performances of tools,the cutting performance of the TiAlCrN coated tools are better than TiAlN coated tools,and the TiAlN coated tools are better than TiCN coated tools.The simulation results show that under the same cutting parameters,the cutting force,cutting temperature and tool stress on the uncoated tool are the largest,followed by the TiCN coated tool,and the TiAlN coated tool is the smallest.The conclusion that the cutting temperature and cutting force on the TiAlN coated tool is smaller than that of the TiCN coated tool coincides with the cutting test results.(3)Compared with the service life of the uncoated cutted tools,the service life of the TiAlCrN coated tools is more than doubled,the TiAlN coated tools is approximately doubled,and the TiCN coated tools is extended by approximately 50%.The main wear patterns of TiAlCrN coated tools are boundary wear and oxidative wear,the TiAlN coated tools are mainly diffusion wear and oxidation wear,and the TiCN coated tools are mainly oxidation wear.