Study On The Mechanism Of Improving The Adhesive Strength Of TiAlN Tool Coatings By Plasma-assisted Laser Substrate Texturing

The physical vapor deposition(PVD)TiAlN coating material with excellent tribological properties is currently one of the most widely used tool coatings for high-speed precision machining of difficult-to-machine materials.However,due to the different bonding types of the film-substrate,thermal expansion coefficient,wetting properties,etc,TiAlN coating tools still have the problem of insufficient film-base bonding strength.This paper combines plasma-assisted laser texturing with PVD coating technology,puts forward a new concept of plasma-assisted laser texturing TiAlN coated tools on the substrate surface.Explores the factors that affect the bonding strength between the coating and the substrate film-substrate and strengthening mechanism with film-based interface.The main experimental methods include:control variable method,comparison method and induction method;the main research contents and conclusions are as follows:(1)Embarked from the improvement of film-based physical bonding and chemical bonding interface,a new idea of plasma-assisted laser textured substrate pretreatment to enhance the coating tool film-based bonding strength is proposed.Nano-pulse laser was adopted to process micro-texture on the surface of the substrate,and the effect of various laser processing parameters on texture morphology and quality was compared and analyzed,and then the optimal laser processing parameters that were beneficial to coatings were obtained.The process parameters of UV nanosecond laser texturing are:pump current 1 A,scanning speed 50 mm/s,repetition frequency 30 KHz,pulse width 5 ns.The obtain size of micro texture is:groove width with 35 ?m,groove depth with 6 ?m.For the purpose of studying the effect of the texture pitch of the substrate surface on the bonding strength of the coating,four micro-textured surface with different groove pitches of 50 ?m,100 ?m,150 ?m and 200 ?m were comparative analyzed.After the micro-textures were prepared on the substrate surface,the surface of the textured substrate was etched by using an inductively coupled plasma etching system.The etching parameters were:upper RF source power 500 W,lower RF source power 150 W,and air pressure 3 Pa.The etching temperature is 40?,the etching time is 20 min,the gas flow is 20 sccm,and the etching gas is SF6.The micro-textures quality of the substrate surface were significantly improved after etching.(2)Objective to compare and analyze the physical and chemical properties of each substrate surface,the following different treatments are performed:1.Substrate surface laser texturing;2.Substrate surface plasma etching;3.Plasma-assisted laser texturing substrate pretreatment;4.Grinding and polishing for substrate surface only.Systematically analyzed the material properties and surface state such as residual stress,crystal structure,specific surface area,free energy of substrate surface and so on.The results showed that the plasma-assisted laser texturing pretreatment on the substrate surface can provide the substrate with a better mechanical anchoring effect for the coating,increase the chemical compatibility of the coating and substrate,and improve the specific surface area and surface energy of the substrate surface.(3)TiAlN coating the surface of the above four different pre-treated cemented carbide substrates,named after coating:conventional coated cutting tool(CCT),laser texturing coated cutting tool(LCT),plasma etching coated cutting tool(CECT),plasma etching-assisted laser texturing coated cutting tool(LECT).And then,carry on nano-scratch tests and dry cutting 316L austenitic stainless steel tests.The results showed that,the film-based bonding strength of the LECT sample(critical load:112.64 N)has been significantly improved comparing with the CCT sample(critical load:80.52 N).In the cutting tests,compared with the CCT tool,under the cutting speed of 200 m/min,the cutting force Fx,F,and Fz of the LECT-100(texture groove spacing is 100 ?m)tools showed the most significant reductions,reducing 34.82%,36.15%and 11.36%respectively.And,significantly reduction of the coating peeling area and wear degree of rake and flank tool.Based on the film-based interface theory and the coating adhesion mechanism,the plasma-assisted laser-texturing TiAlN coating tool film-based interface strengthening mechanism which considering the physical bonding and chemical bonding was revealed.