Influence Of Different Al-containing Transition Layers And Pre-and Post-treatment On The Structure And Properties Of AlCrN Coating

In this paper,multi-arc ion plating technology was used to prepare AlCrN coatings with different Al transition layers on high-speed steel tools,and various pre-treatments and post-treatments were performed on the AlCrN coating to increase the adhesive strength of the coating and reduce the surface roughness,which further improved the cutting performance of the coated tool.XRD,SEM,EDS,friction and wear experiments were used to explore the effects of addition of different Al-containing transition layers,various preand post-coating treatments on the structure,morphology,roughness,adhesive strength,microhardness,friction and wear properties of AlCrN coatings.In addition,milling experiment against 20 Cr Mo was also performed to evaluate the the AlCrN coated tools,and the cutting mechanism was discussed in detail.Some conclusion were achieved as follows:(1)The adhesive strength of AlCrN coatings(C1-C4 coating)with different Al transition layers reached the grade of HF-1,and the thickness of the coating was about3.8?4?m.As the Al content in the transition layer increased,the hardness of the AlCrN coating increased,and the(111)diffraction peaks of the coating shifted to high angles with no obviouse phase change;the C3 coating showed the smallest surface roughness(Sa:0.124?m,Sq: 0.213?m)and coefficient of friction(0.662),as well as the best cutting performance.The milling results showed that obvious coating delamination could be found for all the coated cutters during and after cutting process;at the same time,the machined material of 20 Cr Mo adhered to both the surfaces of the substrate and the coating,which resulted in the adhesive wear.Therefore,the C3 coating with the smallest surface roughness,the lowest friction factor and the best interlayer structure shows the best cutting performance.(2)Thickness of the all AlCrN coatings after wet sandblasting,dry sandblasting and shot blasting pre-treatment on substrate is 3.8?m.After different pre-treatments,the surface roughness and micro-hardness of the substrate increased.The substrate roughness(Sa:0.053?m,Sq:0.075?m)and micro-hardness(801.5HK)after wet sandblasting pretreatment were the smallest.While,the roughness(Sa:0.831?m,Sq: 1.010?m)and hardness(880.1HK)of the pre-treated substrate by shot peening were the largest.The roughness of the AlCrN coating on the pre-treated substrate showed the same change trend as the substrate;Various pre-treatments has no effect on the phase structures of the AlCrN coatings,but the diffraction peaks of the AlCrN coatings pre-treated by dry sandblasting and shot peening shifted towards a low angle with the preferred orientation from(111)plane to(200)plane;Secondly,wet sandblasting and dry sandblasting could improve the adhesion of the AlCrN coatings to the substrate.The friction coefficient of AlCrN by wet sandblasting pretreatment showed the smallest value of 0.619 with the wear mechnism of abrasive wear;and the main wear mechnism of AlCrN coating by dry sandblasting and shot peening was adhesive wear.The AlCrN-coated tool by dry sandblasting pretreatment showed the best cutting performance due to its good adhesion and tribology performance.,and the cutting performance also improved by about 10% compared with the untreated AlCrN-coated tool.(3)Different post-treatment methods can effectively remove particles on the AlCrN coating surface.Among them,wet sandblasting,shot peening and dry sandblasting had better effect on clearing the "micro-particles",and the number of "micro-particles" were reduced by 91.1%,88.5% and 86.9%.While,ion etching could only reduce the "micro-particles" by 21.0%.The XRD patterns of the AlCrN coatings revealed the solid solution(Al,Cr)N phase,but the diffraction peaks of the AlCrN coatings all shifted to a low angle.The coefficient of friction of the post-treatmented coating reduced as compared with the untreated coating;the wear mechanism of the coatings were abrasive wear with a small amount of oxidative wear.The cutting life of AlCrN coated tools has been improved to varying degrees after the post-treatment process.Compared with the untreated coated tools,the cutting life of the coated tools after particle shot blasting,dry sandblasting,ion etching,and wet sandblasting are respectively increased by about 30%,40%,40% and60%.Comprehensive pre-treatment,different Al-containing transition layers and post-treatment processes are used for composite treatment of AlCrN tool coatings,and its cutting life can reach 16 m,compared to AlCrN tool coatings with only pre-treatment,different Al-containing transition layers or post-treatments the cutting life has been improved.