Study On Preparation And Cutting Properties Of Gradient TiAlSiN Coatings

In this paper,the TiAlSiN coatings with different Al containing gradient structures(reffered as T1,T2,T3)and different Si containing gradient structures(reffered as T1,T2,T3)were deposited on the cemented carbide tool substrate,which could help to improve the adhesion and enhance the cutting performance of the coated tools.Mmicrostructure,morphology,residual stresses,adhesive strength,hardness,friction and wear properties of TiAlSiN coatings with different Al and Si containing gradient structures were studied in detail by using X-ray diffraction,scanning electron microscopy,energy dispersive spectroscopy,friction and wear test.At the same time,milling and drilling experiments of the coated tools against cast iron HT250 on the MCV850 vertical milling machine were applied to study the influence of coating structure on cutting performance and the cutting mechanism.The results were summarized as follows.The phase structure of TiAlSiN multilayer coating with different Al containing gradient structures is solid solution(Ti,Al)N phase.As the Al content increases,the diffraction peack of the(Ti,Al)N phase shifts to the right.Among all the coatings,the phase of the gradient structure coating with a large change in Al content(T1 coating)is TiN phase in the(111)crystal plane direction.The phases of the gradient structure coating(T2 coating)with a smooth change in Al content are(Ti,Al)N phase and AlN phase.The phase of the gradient structure coating(T3 coating)with no obvious change in Al content is AlN phase.T3 coating exhibits the lower residual stress and higher adhesive strength(HF-2).T2 coating shows good wear resistance.Milling results display that the wear mechanism of coated tools is mainly characterized by abrasive wear and adhesive wear.T3 coating has the longer milling life at 80 m/min and 110 m/min.Drilling results show that the T2 coating has the best drilling performance and a small amount of built-up edges remains at the main cutting edge.The phases structure of TiAlSiN multilayer coating with different Si containing gradient structures are solid solution(Ti,Al)N phase and AlN phase.Among all the three coatings,the S3 coating with low Si content gradient structure exhibit high hardness,good adhesive strength,low residual stress and low friction coefficient.The milling results show that the typical wear mechanism of the coated tool are mainly represented by adhesive wear.The S1 coating was represented by a small amount of built-up edges and coating peeling.The S2 coating was invalided by coating peeling.The S3 coating was represented by built-up edge,coating peeling and microcrack.S3 coating exhibits the better milling performance at cutting speeds of 80 m/min.When the cutting speed increased from 80 m/min to 110 m/min,the milling length is nearly twice.Drilling results show that the S2 coating has the best drilling performance and coating peeling is the main failure mechanism.