Preparation,Characterization And Performance Of Coatings On Cemented Carbide Cutting Tools For Titanium Alloys

Due to superior strength to weight ratio,exceptional corrosion resistance and excellent fracture toughness,titanium alloys are used in major industries,including the aeronautic automotive,chemical and biomedical industries.However,titanium alloys are classified as difficult-to-cut materials,which arises their costs and restricts their development and application.Coated cemented carbide cutting tools are the most suitable tools for cutting titanium alloys.By depositing a high hardness coatings,it could improve mechanical properties and prolong the lifetime of cutting tools.So it is very important to develop a cutting tool coating for cutting titanium alloys.As the backgrounds mentioned above,Ti based and Cr based coatings are synthesized by magnetron sputtering.The influence of Si and Ta contents,monolayer or multilayer growth mode,and annealing on morphologies,phases,hardness,H3/E2 and adhesive strength are discussed.A research that whether annealing can improve mechanical property of monolayers and multilayers coatings is also studied.The following conclusions can be drawn:(1)The hardness of TiAlSiN coating increases with Si contents firstly,then it decreases.When the Si content is increased to 5.8 at.%,the hardness reaches a maximum of 22.5 GPa.The hardness of CrAlSiN increases to 16.9 GPa with increasing Si contents.The hardness of TiAlTaN and CrAlTaN increases with Ta contents.The maximum hardness of 32.8 GPa and 33.8 GPa are obtained when Ta contents are 17.4 at.%and 12.0 at.%,respectively.(2)The adhesive strength of TiAIN coating with the substrate is 89 N.However,a low adhesive strength value of 31 N is obtained for the CrAIN coating.The adhesive strength of TiAlSiN increase firstly,then it decreases with increasing of Si content.The adhesive strength of CrAlSiN decreases with increasing Si content.So does the TiAlTaN with increasingTa content.But the adhesive strength of CrAlTaN changes slightly with increasing Ta content.(3)Adding Si or Ta into the coating of TiAlN andCrAIN can improve the ability of antioxidation.(4)With the increasing of annealing temperature,the hardness of TiAlN/Si coating increases.And it reches its maximum hardness at temperature of 700 ?,which has increase by 23%than the as-deposited one,then it decresses.The hardness of TiAlN/Si increases first and then decreases with increasing of annealing duration.The best annealing duration is 60 min.The hardness of TiAlN/Ta,CrAlN/Si,CrAlN/Ta coating increase after anneaed at 700 ?for 60 min.The adhesive strength of CrAlN/Si,CrAlN/Ta coating can be improved after annealed.However,mechanical properties of TiAlSiN,TiAlTaN,CrAlSiN,CrAlTaNcannot be improved after annealed.