Study On Fabrication And Application Of TiAiN Coated Tools With Textured Substrate Surface

The concept and design idea of the TiAIN coated tools with a laser-textured substrate surface are proposed in this paper,and the TiAIN coated tools with a laser-textured substrate surface are developed combined with the preparation technologies of surface textures and surface coatings.The substrate surface texturing can change the morphology of the substrate surface,increase the specific surface area of the substrate,thus improve the adhesive strength between TiAIN coatings and substrate;meanwhile,it can also change the contact characteristics of the tool-chip interface,improve the lubricity property of the cutting tool.The mechanical properties,tribological behavior and cutting performance of the developed cutting tools are investigated.The possible mechanisms for the effects of surface textures are discussed.Based on the requirements for the properties of the TiAIN coated tools,the design principals of the TiAIN coated tools with a laser-textured substrate surface are proposed.WC/Co cemented carbide that has good mechanical properties is confirmed as the tool substrate material,and the chemical and physical compatibility of the coating materials system are analyzed,which further verifies the good matching between WC/Co cemented carbide and TiAIN coatings.The effect of the laser process parameters on the evolution of the micro-scale textures induced by nanosecond laser and nano-scale textures induced by femtosecond laser is investigated,and the optimum laser process parameters for the uniform micro-scale textures and nano-scale textures are obtained.For optimum nanosecond laser process parameters:voltage is 8 V,scanning speed is 15 mm/s,frequency is 7000 Hz and the overscan is 2;according to the process parameters,the width of the microtextures is about 50 ?m,and the depth is about 48.9 ?m.For optimum femtosecond laser process parameters:pulse energy is 2.5 ?J,scanning speed is 500 ?m/s,scanning space is 5 ?m and the overscan is 1;according to the process parameters,the period of the microtextures is about 550 nm,and the depth is about 150 nm.The micro-scale textures,nano-scale textures and micro/nano-scale textures are fabricated on the WC/Co substrate surface according to the optimum parameters.TiAIN coatings are successfully deposited by the cathodic vacuum arc ion platingtechnique on the laser-textured substrate surface,thus the TiAlN coated tools with a laser-textured substrate surface are developed:the TiAIN coated tools with micro-scale textured substrate surface,named MCT;the TiAlN coated tools with nano-scale textured substrate surface,named NCT;the TiAlN coated tools with micro/nano-scale textured substrate surface,named MNCT.The effect of surface textures on the mechanical properties of the TiAIN coatings is studied.Results show that surface textures on the substrate surface can increase the surface roughness and H/E ratio of the TiAlN coatings,and also lead to the formation of WC1-x phase on the substrate appearing approximately at the same position of the TiAIN peaks;the adhesion strength between the TiAIN coatings and the laser-textured substrate(measured by the scratch tests)was better than that of the standard tool due to mechanical anchoring mechanisms and chemical modification in the carbide exposed grains.The effects of surface textures on tribological properties of TiAlN coated samples in sliding against AISI 316 austenitic stainless steel are studied.The following conclusions are obtained:"NCT sample shows a higher wear life compared with CCT sample,which is due to the higher coating-substrate adhesion of the NCT sample in comparison to the CCT sample;The MoS2 solid lubricants burnished on the TiAlN coated sample can effectively reduce the friction coefficient compared with the samples without MoS2 solid lubricants,especially for the MCT sample with micro-scale textures.The presence of micro-scale textures on sample surface can efficiently release and transfer the solid lubricants stored in the grooves to the contact region to maintain the lubricant film,and trap the wear debris,which are the reasons why the tribological properties of the MCT sample are better than that of the CCT sample;Compared with the NCT and MCT samples,the MNCT sample has better tribological properties,due to the benefiting from both nano-scale and micro-scale textures.Cutting tests are carried out on AISI 316 austenitic stainless steel with the untextured TiAlN coated tool(CCT).the TiAIN coated tools with micro-scale textured substrate surface(MCT),the TiAIN coated tools with nano-scale textured substrate surface(NCT),and the TiAlN coated tools with micro/nano-scale textured substrate surface(MNCT).Results show that the cutting forces,friction coefficient between the tool-chip interfaces,and quality of machined surface of the developed TiAlN coated tools are significantly improved over that of the conventional one.Compared to the CCT tool,the Fe adhesion and adhesive wear on the developed TiAIN coated tools are observably decreased,and the MNCT tool with micro/nano-scale textures on the substrate shows the best anti-adhesive property among all the tools tested.The effect mechanism of the MNCT tool is illuminated.On the one hand,during the cutting process,the presence of micro-scale textures on tool rake face can efficiently promote the lubricating fluids filtering into the tool-chip interface and forming the boundary lubrication,decrease the contact areas between the tool-chip interface,and trap the wear debris;on the other hand,the nano-scale textures on the substrate can increase the adhesive strength between the TiAIN coatings and WC/Co substrate,and then reduce the adhesive wear of the TiAIN coated tool and maintains the integrity of the TiAIN coatings to protect the tool substrate.