Microstructure Control Preparation And Properties Of Self-organized Nano-multilayer AlCrSiON Coating

With the wide application of refractory materials such as high temperature alloys and titanium alloys in the fields of aerospace,nuclear power,vehicles and other fields,as well as the high demanding of high-speed and high-efficiency cutting processing advocated by modern equipment manufacturing industry,it is imperative to develop the coating material of the cutting tools with high mechanical properties and high temperature thermal stability to adapted to the increasingly severe cutting conditions.Traditional nitride coatings have good room-temperature mechanical properties,but the hardness is significantly reduced at high temperatures and easily gets oxidized.Although oxide coatings have good thermal/chemical stability,their mechanical properties are poor.Therefore,this work focuses the composition and microstructure of coatings to improve the mechanical properties and high temperature thermal stability of the coated tools.Firstly,the effect of oxygen content on the composition,microstructure and properties of the coating was studied by doping oxygen in the Al Cr Si N coating;After doping with oxygen,a self-organized N-rich/O-rich alternating nano-multilayer structure formed by the rotation of the substrate was discovered.Then combined with the characteristics of the ion source that can improve the reaction gas ionization rate,the ion source assisted deposition of Al Cr Si ON coating was used.The effects of ion source on the composition,microstructure,mechanical properties,high-temperature thermal stability and friction and wear properties of Al Cr Si ON coatings were compared and studied.Finally,the modulation period of the nano-multilayer was adjusted by changing the rotation rate of the substrate during deposition,and the effects of the modulation period on the composition,microstructure,and mechanical properties of the nitrogen-and oxygen-rich self-organized Al Cr Si ON nano-multilayer coatings were investigated.The main research conclusions of this paper are as follows:1)Al Cr Si ON coatings with different N₂/O₂flow ratios were prepared using arc ion plating technology.The effects of oxygen content on coating composition,microstructure,mechanical properties,high temperature thermal stability,and oxidation resistance were studied.The results show that after doping 9.77at.%of oxygen in the Al Cr Si N coating,a nanocomposite structure and a self-organized N-rich layer/O-rich layer alternating nano-multilayer structure formed by the rotation of the matrix were found,moreover,the multi-layer interface grows locally coherently and epitaxially;the hardness of the coating first increases and then decreases with the increase of the oxygen content,and reaches a maximum value of 36.1±0.98GPa when the N₂/O₂flow ratio is 291/9;the elastic modulus of the coating decreases with the increase of the oxygen content.The H³/E*²values of the oxygen-doped coatings are larger than Al Cr Si N coatings.In terms of thermal stability,the tendency of w-Al N phase formation and Cr-N bond decomposition after oxygen doping is significantly reduced.After annealing at 1000?,the phase structure and hardness of the coating with oxygen content greater than 40at.%had not changed significantly,it indicates that the doping of oxygen and the formation of self-organized nano-multilayer structure improve the thermal stability and high-temperature mechanical properties of the coating.After isothermal oxidation at 1000?for 5 hours,only a thin and dense oxide layer was formed on the surface of the Al Cr Si ON coating(oxygen content?40at.%),Which is much smaller than the thickness of the oxide layer of the Al Cr Si N coating.2)In order to explore the mechanism of ion source on the composition and properties of Al Cr Si ON coatings,Al Cr Si ON coatings with different N₂/O₂flow ratios were prepared by ion source assisted deposition.The results show that the ion source-assisted deposition has no significant effect on the surface morphology and phase structure of the coating,but the modulation period of the self-organized nano-multilayer and the thickness of the O-rich layer are significantly increased when the ion source is not opened.The hardness of the coating first increased and then decreased with the increase of oxygen content,and reached a maximum value of 35.0±0.98GPa when the N₂/O₂flow ratio was 291/9;the elastic modulus of the coating gradually decreased with the increase of oxygen content.Compared with the unopened ion source,the coating with an N₂/O₂flow ratio of 291/9 only shows a significant w-Al N diffraction peak after annealing at 1100?;after annealing at 1000?,the phase structure and nanohardness of the oxygen-rich coating(oxygen content greater than 40%)have not changed significantly,and it indicates that ion source-assisted deposition and oxygen element doping significantly improve the high temperature thermal stability of the coating.Compared with Al Cr Si N coating,the average friction coefficient of oxygen-doped coating at room temperature is reduced by?0.1.3)Based on the self-organized structure of Al Cr Si ON coatings,nitrogen-rich and oxygen-rich self-organized Al Cr Si ON nano-multilayer coatings with different modulation periods were prepared by changing the rotation rate of the substrate.The effects of the modulation period on the coating composition and properties were studied.Nitrogen-enriched Al Cr Si ON coatings grow in a columnar morphology.With the increase of the substrate rotation rate,that is,the reduction of the nano-multilayer modulation period,the oxygen content in the coating increased slightly,and the N content decreased slightly.The hardness of the coating showed a trend of first increase and then decrease,and reached a maximum value of 35GPa when the substrate rotation speed was 3r/min.The H³/E*²values of all coatings were greater than 0.2GPa,showing great toughness.The modulation period has little effect on the surface quality and the content of each element of the oxygen-rich self-organized Al Cr Si ON coating.Due to the higher oxygen content,the coating grows in an amorphous glass morphology.The hardness of the coating showed a tendency of a slight increase at first and a slight decrease with the increase of the substrate rotation rate,but all remained between 29 and 31 GPa.Film-substrate bonding strength of all coatings is good,and its bonding force is maintained at about 60?70N.