Research On Friction And Wear Characteristics Of Multicomponent Nitride Coatings And Properties Of Coated Tools

Coated tools have attracted much attention due to their high surface hardness,good wear resistance,low friction coefficients and low thermal conductivity,as well as excellent cutting performance.As a chemical barrier and thermal barrier,coating materials can reduce the diffusion and chemical reaction between the tool and the workpiece,thus decreasing the tool wear and extending the service life of the tool.In addition,the cutting accuracy,cutting efficiency and tool applicability of coated tools are more excellent than traditional tools,so the research on coating materials and coated tools is of great significance,which is also the current research hotspot in the field of cutting.In this paper,AlCrN,TiAlCrN and TiAlSiN coatings were deposited on the surface of the specimens' of 30 CrMnSi steels and cemented carbide cutting tools by PVD technology.And the following experiments have been carried out in current work:(1)The surface morphologies of the three coatings were observed by scanning electron microscope,the element compositions and mass fraction of the coatings were measured,the surface hardness,thickness and adhesion strength of the coatings were determined as well.(2)Through reciprocating friction and wear tests,the evolutions of friction coefficients,wear amounts and wear rates of AlCrN,TiAlCrN and TiAlSiN coatings under different normal loads,reciprocating speeds and test temperatures were investigated,and the wear morphologies and wear mechanisms of the coatings under different loads were also analyzed.(3)The effects of different cutting parameters on the cutting forces,cutting temperatures and workpiece surface roughnesses of uncoated cutting tool and three kinds of coated tools were studied by dry cutting tests with single factor experiment method,the prediction models of the workpiece surface roughnesses for AlCrN,TiAlCrN and TiAlSiN coated tools were obtained by the response surface method,which were validated by tests.(4)The flank wears VB of uncoated tool and AlCrN,TiAlCrN and TiAlSiN coated tools were measured and analyzed,and the wear morphologies of tools were observed by scanning electron microscopy and the wear mechanisms were investigated as well.Based on the above researches,the following conclusions can be gotten:(1)It can be seen that the surfaces of the three coatings were flat and fine and the thicknesses were similar through observations and experiments.The microhardness was arranged in order of AlCrN coating>TiAlCrN coating>TiAlSiN coating>uncoated substrate;while the adhesion forces was arranged in order of TiAlCrN coating>AlCrN coating>TiAlSiN coating.(2)Under the conditions of different normal loads,reciprocating speeds and test temperatures,the order of friction coefficients of specimens was as follows: AlCrN coating<TiAlCrN coating<TiAlSiN coating< uncoated substrate;The wear amount and wear rate of AlCrN coating was the lowest,followed by TiAlCrN coating and TiAlSiN coating.The main wear forms of TiAlCrN coatings were oxidation wear and abrasive wear,the AlCrN coatings were oxidative wear and abrasive wear and the TiAlSiN coatings were oxidation wear,diffusion wear and abrasive wear.(3)The cutting performances of coated tools were better than uncoated tools,the cutting performances of AlCrN coated tool were slightly better than TiAlCrN coated tool,while the TiAlCrN coated tool was better than TiAlSiN coated tool.The prediction models of the workpiece surface roughness for AlCrN,TiAlCrN and TiAlSiN were obtained by the response surface method and the errors of the three models were 2.45%,3.09% and 3.07%,respectively.(4)When machining the 30 CrMnSi steels,the service life of TiAlSiN coated tool increased 75% than that of uncaoted tool,and the service life of AlCrN coated tool increased approximately 125% than uncoated tool,while the TiAlCrN coated tool increased more than 125% than uncoated tool.The main wear patterns of uncoated tool were diffusion wear and oxidation wear,accompanied with slight abrasive wear,both of AlCrN and TiAlSiN coated tools were crater wear,oxidation wear and diffusion wear;while the main wear forms of TiAlCrN coated tool were boundary wear,oxidation wear and diffusion wear.