Preparation And Study Of Multilayer Nanocomposite TiB₂ Tool Coating

TiB₂ possess the advantages of high hardness,low miscibility with titanium metal,and weak elemental diffusion,which has great potential in cutting titanium alloy.In this research,TiB₂ deposition coating parameters are optimized by ion beam assisted DC magnetron sputtering to prepare TiB₂ tool coating with fine grain structure firstly.Secondly,based on the TiB₂ coating inserting different layers of AlCrYN Coatings,which have higher temperature oxidation resistance and bonding strength,Finally,the TiBN/AlCrYN nanocomposite multilayer coating was prepared by combining the advantages of TiB₂ and AlCrYN coatings.The structure and properties of TiB₂ coating are studied in detail.The main findings are as follows:?1?The TiB₂ coating was deposited by ion beam assisted DC magnetron sputtering.The physicochemical properties,high temperature properties and cutting properties of the coatings were studied.The results show:coating exhibits a polycrystalline hexagonal structure,and the ion source assists the coating to significantly change the crystallinity of the coating and refining the grains.As the ion source's current increases,hardness and residual stress of the coating show a change of the first increase and then decrease.In addition,the ion source assisted deposition of TiB₂ has better high temperature oxidation resistance.The TiB₂ coating can effectively improve the cutting life of the tool when cutting the TC4 alloy,and the ion source-assisted deposition of the TiB₂ coated tool exhibits better cutting performance.?2?In order to improve the high temperature oxidation resistance and bonding strength of TiB₂ coating,alternating multilayer structure of AlCrYN and TiB₂ coatings is prepared.Study on the effect of inserting AlCrYN layer on the physicochemical properties,high temperature properties and cutting properties of the coating.The results show that with the increase of the AlCrYN soft phase insertion layer,the bonding strength increases remarkably.However,the hardness and elastic modulus of the coating also decrease accordingly.Inserting a coating with less AlCrYN?0,1 layer?at room temperature showed better wear resistance,while at 500°C,due to the self-lubricating Al₂O₃ and B₂O₃ layers,the coating with a large number of AlCrYN layers had a lower wear rate(1.97×10^-5mm³/N·m).In addition,the AlCrYN intercalation layer can form a dense Al₂O₃ film which effectively hinders the diffusion of oxygen into the interior of the coating.However,at 950°C,evaporation of liquid B₂O₃ leads to a large number of pores,which accelerates the oxidation of the coating,making the series coating completely ineffective below 1000°C.TiB₂-AlCrYN multilayer can improve the adhesion of the coating on the tool,which leads to the effective improvement of the cutting life of the tool during the cutting of TC4 alloy.?3?The TiBN/AlCrYN nanocomposite multilayer coating was prepared based on TiB₂ high hardness and high temperature thermal stability of AlCrYN,and the physicochemical properties of the coating were studied.Experiments show that the bond strength of the coating increases remarkably as the modulation period decreases.The friction coefficient decreased significantly due to formed self-lubricating Al₂O₃ and B₂O₃layers during the 800°C friction test.The coating has higher oxidation activation energy as the modulation period decreases,showing better high temperature oxidation resistance.In addition,the TiBN-AlCrYN nanocomposite coating can effectively improve the cutting life of the tool in processing TC4 alloy.In summary:the ion source-assisted deposition coating has a high hardness and has a large application prospect in cutting TC4 alloy.However,TiB₂ has disadvantages such as low bonding strength and poor high temperature oxidation resistance.Inserting AlCrYN coating can effectively improve the high temperature oxidation resistance of the coating,TiBN/AlCrYN nanocomposite can effectively improve the bonding strength of the coating,and can effectively reduce the wear of the coating at high temperature and improve the cutting life of the TiB₂ based coating tool.