Study On The Structure,Performance And Mechanism Of The Nanocomposite Cutter Coatings

With the rapid development of modern processing and manufacturing industry,the requirements on cutting tool performance are getting higher and higher.The coated cutting tools can effectively improve the processing quality,adapt to various processing conditions and prolong the service life.This paper mainly improved the toughness of the ZrB₂ coating,and developed Zr-B-N nano composite coatings with different structures and properties.Zr-B-?N?nano-composite coatings with different structures and compositions were prepared by High Power Impulse Magnetron Sputtering?Hi PIMS?and Pulsed DC Magnetron Sputtering?PDCMS?composite systems.The surface and cross-sectional morphology of the coatings were observed by field emission scanning electron microscopy?FE-SEM?.The chemical composition of the coatings was analyzed by energy dispersive spectroscopy?EDS?.The phase composition of the coatings was detected by X-ray diffractometer.The X-ray photoelectron spectroscopy?XPS?was performed to investigate the spectra and bonding states of the coatings.The microstructure of the coatings was observed by transmission electron microscopy?TEM?,the morphology and surface roughness of the coatings were observed by atomic force microscopy?AFM?.The hardness of the coatings was measured by nanoindentation;the adhersive strength was tested by the scratch tester;the residual stress was measured by the thin film stress meter.The tribological behavior of the coatings was tested by a high temperature friction and wear tester.The oxidation resistance of the coating was analyzed by the high temperature muffle furnace.The single-target?ZrB₂?PDCMS system was used to prepare ZrB₂ coating with high hardness?40 GPa?and low toughness.After the reaction gas was introduced,the coatings'hardness and grain size decreased,the average friction coefficient decreased firstly and then increased.The coating at N₂ flow of 5 sccm maintained a higher hardness and a lower coefficient of friction.The Zr-B-?N?coatings with different N contents were prepared by combining system of HiPIMS and PDCMS.The maximal hardness reached 25.35 GPa,which was attributed to the formation of nano-composite structure.After doping N element,all the coatings possessed the compressive stresses,and critical load increased gradually with increasing N content in the coating.The Zr-B-N coating presented the best wear resistance as the N₂ flow was 6 sccm.The influence of the nitrogen flow ratio and temperature during heat treatment on microstructure of the Zr-B-N coatings was studied.The results show that the oxide layer began to form on the coating surface when the heat treatment temperature at 600?,and part of zirconium ions reacted with oxygen to generate Zr₃O?116?crystal.When the N₂ flow was 6sccm,the coating consisted of most of amorphous phase after heat treatment;when the nitrogen flow was 10 sccm,with the increase of heat treatment temperature,the structure of the coating was looser and the section morphology became coarser.The more nitrogen partial pressure,the more dense the coating structure is,the stronger the antioxidant capacity.At the heat treatment temperature of 800?or higher,the cracks occurred on the coating surface,part of the coating separated from the substrate and the coating failed.Two Zr-B-N coatings were grown in mixed Ar/N₂ discharges using hybrid HiPIMS and PDCMS.Firstly,the Zr and ZrB₂ targets connectted in HiPIMS and PDCMS,respectively;then the two targets were exchanged each other.The results indicated that the power supply mode had a significant influence on the coating compositions,microstructure and performance.In the case of Zr-HiPIMS/ZrB₂-PDCMS,the coating possessed the smooth surface,dense microstructure,higher coating hardness and critical load of about 20 GPa and 85.6 N,respectively,because the nanocomposite structure was formed namely the segregated nanograins encapsulated in the amorphous BN phase.For the case of Zr-PDCMS/ZrB₂-HiPIMS,the obvious loose columnar crystals and a relatively rough surface were observed which resulted in the inferior mechanical properties.In addition,the both Zr-B-N coatings possessed the low compressive stresses.