Formtion of Wer-Resistnt TiN nd (Ti1-x, Alx)N Cotings Using DC Filtered Vcuum Arc Plsm 1 A.I. Rychikov, N.N. Kovl*, I.B. Stepnov, I.M. Gonchrenko*, D.O. Sivin, I.A. Rychikov, I.A. Shulepov Nucler Physics Institute, 2 Lenin ve., Tomsk, 635, Russi, Phone: (7-3822) 423963, Fx: (7-3822) 423934 E-mil: rdug@npi.tpu.ru * Institute of High Current Electronics, 4 Akdemichesky ve., Tomsk 6355, Russi Phone: +8-3822-492792, Fx: +8-3822-49241, E-mil: kovl@opee.hcei.tsc.ru Astrct The pper presents the results of investigtion of structure, element composition nd physico-mechnicl properties of TiN nd (TiAl)N cotings deposited under comined tretment of surfce y vcuum rc dischrge nd gseous microprticle-free metl plsm flows. Also, perspectives of industril ppliction of comined technologies re discussed. Gseous plsm flow ws formed using the PINK plsm genertor sed on non-sustinle rc dischrge with glow cthode [5]. The system of rective gs input through gseous rc cthode ws relized in the design of the plsm genertor [6]. 1. Introduction DC vcuum rc dischrge (VAD) plsm hs een used for industril coting deposition for more thn 25 yers. Use of TiN s coting mteril llows decrese friction, wer, increse corrosion resistnce of mterils, protect sustrte from overheting, nd improve decortive properties of rticles [1, 2]. Unfortuntely, use of dc VAD for such modern cotings s (TiAl)N, TiC, CrN, (TiC)N, (TiAl)N, ZrN, MoS 2, DLC, including multilyered ones, is ounded y prmeters of existing technologicl equipment nd methods of coting deposition. Cotings deposited using conventionl technologies re chrcterized y low dhesion strength, high roughness, heterogeneous structure, nd low wer resistnce. The pper presents the results of investigtion of chrcteristics of TiN nd (TiAl)N cotings deposited using industril set-ups for ion nd plsm coting deposition equipped with devices for clening plsm from microprticle frction nd PINK-type gseous plsm genertor. 2. Equipment nd Experimentl Methods The investigtions were crried out using the ННВ6,6- И1 industril set-up for ion nd plsm coting deposition. Fig. 1 shows the schemtic of the experimentl set-up. Metl plsm ws generted y three dc VADsed vcuum rc evportors (VAE). To clen vcuum rc plsm from microprticle frction, the VAEs were equipped with plsm filters (PF) of the shutter type [3, 4]. Fig. 1. Schemtic of the experimentl set-up For the regime of ion nd plsm coting deposition we pplied negtive potentil onto smples. We used voltge source with the device of rc utomtic extinction nd device protecting from overvoltge resulting from rc current rekdown. Pressure in the vcuum chmer ws creted using diffusion oil nd vpour pump Н-25/25СО. The temperture of smples ws controlled y pyrometer Smotrich. Tle 1 shows min technicl chrcteristics of the set-up. Element composition of cotings ws defined y lyered electron Auger spectrometry using the spectrometer Shkhun-2. Smple surfce microstructure nd morphology were investigted y opticl microscopy nd 3D profiling with resolution up to 1 nm using MICRO MEASURE 3D Sttion (STIL). Coting hrdness ws mesured using Nno Hrdness Tester (CSEM) with the Vickers indenter t lodings of 1 mn. In investigte coting dhesion strength we used the scrtch method with the help of Rockwell 1 The work ws supported y wrd of CRDF RR2-994, wrd of the Ministry of Eduction of RF for the Federl Gol Progrm Integrtion No. Л59, nd wrd of Tomsk Region Administrtion. 4
Orl Session indenter with the dimeter of µm t time-dependent loding in the rnge of 2 N using Micro Scrtch Tester (CSEM) [7]. Triotechnicl chrcteristics of cotings were investigted using PC-Operted High Temperture Triometer (CSEM). The friction coefficient ws registered in situ. Smple wer ws clculted y mesuring mteril flow resulting from ppliction of fixed ll onto the rotting smple [7]. Tle 1. Prmeters of the experimentl set-up Metl plsm genertor Dischrge current, А 25 Plsm concentrtion, cm 3 up to 4 1 1 Plsm flow dimeter, mm Decrese in microprticle frction (Ti) 1 2 1 3 Gseous plsm genertor Working pressure re, P 1 2 1 Plsm concentrtion, cm 3 1 9 1 11 Dischrge current, А 5 15 Homogeneity of plsm flow long the cross section, % Gs N 2 5 3. Formtion of TiN nd (TiAl)N Cotings Cotings were deposited onto steel P6M5 smples with the dimeter of 5 mm nd 3 mm thickness, fixed in the center of the rotting tle. Preprtion of smples included surfce mechnicl polishing nd urnishing with rsive pstes АСН /28, 14/1 up to the roughness of R z.7 µm (TiN) nd R z.43 (TilN) nd chemicl clening in ultrsonic th. Smples were clened nd heted in the vcuum chmer using low temperture N 2 plsm t vcuum volume pressure of 1.5 1 2 2.4 1 2 P with negtive potentil on smples equl to 1.2 kv. Temperture of smples ws in the rnge of 45 5 C. For TiN cotings, smple surfce ws simultneously treted y N 2 nd microprticle-free Ti plsm. Bis voltge on smples incresed up to 1.4 kv. Due to ion chrge stte, surfce ws processed minly y smple heting nd ion etching ccompnied y formtion of lrge mount of ctive sorption centers. The temperture of smples ws 58 С. With smooth decrese in is voltge on smples (U ), we oserved formtion of trnsition lyer nd ion ssisted coting deposition. The temperture ws 45 5 С, nd pressure in the vcuum chmer ws equl to 2 1 2 P. (TiAl)N cotings were deposited with the use of two VAEs with Al cthodes nd one VAE with Ti cthode. Cotings were deposited in the rection gs (N 2 ) environment. Rtio of Ti nd Al plsm flows depended on VAD current (I d ). Figure 2 shows the results of investigtion of element composition of TiN nd (TiAl)N cotings. Stochiometric composition of deposited TiN (Ti ~ 45%; N ~ 45%) nd (TiAl)N (Ti ~ 29.5%; Al ~ 27%; N ~ 39%) cotings corresponds to dt on the digrm. Thick trnsition lyers etween the coting nd sustrte show tht the regime of ion ssistnce ws ccompnied y intense diffusion processes ner smple surfce. Concentrtion, % t Concentrtion, % t 8 6 8 6 C Ti Fe N O,,3,6,9 1,2 C Ti Fe Depth, µm N O Al,,2,4,6,8 1, 1,2 1,4 Depth,µm Fig. 2. Element distriution into the depth of the deposited coting: а TiN, (TiAl)N Pper [8] shows the results of diffrction electronmicroscopic phse nlysis of TiN cotings, which show tht when U ws in the rnge of 25 75 V, multi-phse structures composed of δ-titnium nitride (TiN) with grin size of 11 15 nm, respectively, were formed. When U ws equl to 1 V, ε-titnium nitride (Ti x N y ) nd δ-titnium nitride phses re oserved in the cotings, however, size of grins of the former phse is hlf size of grins of the TiN phse. Figure 3 shows the results of morphologicl investigtion of the deposited cotings s profiles nd imges of TiN nd (TiAl)N film surfces. The presented dt confirm tht use of PF results in decrese in surfce roughness y severl times. For (TiAl)N cotings formed without PF, surfce roughness equls to tens of microns. The phenomenon is ttriuted to presence of lrge mount of microprticle frction in Al plsm flow (up to severl tens of percents). For this cse droplet size cn e equl to more thn 1 µm. Use of PF for clening Al plsm llows decrese content of microprticle frction in the flow y severl orders of mgnitude, which permits deposit cotings with the roughness not more thn.64 µm. Comprtive nlysis of curves 1 nd 2 (Fig. 2) shows tht decrese in I d nd increse in U llow significntly decrese surfce roughness of TiN cotings. This effect cn e explined y increse in plsm ion component trnsporttion efficiency in PF electrodes
nd decrese in microprticle frction in the rc plsm flow t the expense of decrese in I d, s well s due to reflection of droplets from negtive potentil ner the smple surfce [9] nd sputtering of microedges on coting surfce. show tht the mesured hrdness corresponds to optiml stochiometric composition of the coting. = 1 A = 9 A = 8 A Smples = 7 A TiN with PF TiN without PF 1 3 Hrdness, kg/mm 2 c Fig. 4. Chnge in hrdness vlues depending on regimes of coting deposition The dt presented t Fig. 4 confirm tht use of PF llows increse TiN coting hrdness y %. It ws lso found out tht increse in U in the rnge of 1 75 V results in decrese in coting hrdness y 15 %. The phenomenon cn e explined y the fct tht in cse of ppliction of gseous plsm genertor, the rtio of metl nd nitrogen toms required for formtion of the coting with optiml stochiometric composition is ensured t decresed pressure of N 2 ; with increse in U we oserve metl growth in the coting, which negtively influences coting hrdness. At the sme time increse in U results in insignificnt decrese in inner tensions in smples, which we demonstrted y compring loding nd unloding curves of the Nno Hrdness Tester indenter (Fig. 5). The phenomenon cn lso e explined y chnge in conditions of phse formtion, in prticulr, y formtion of structures with grins of lrger sizes with the increse in U contrry to conventionl notion on increse in compressing voltges with increse in intensity of heting [8]. Norml force, mn 1 1- TiN - without PF 8 2 - TiN - with PF 6 3- (TiAl)N - with PF 3 1 2 1 3 5 6 Penetrtion depth, µm d Fig. 3. Profile of TiN nd TiAlN coting surfces: without PF, with PF (I d = 125 A, U = 5 V), c with PF (I d = 1 A, U = 8 V), d (TiAl)N Figure 4 presents the results of investigtion of (TiAl)N coting hrdness depending on rtio of Ti nd Al plsm flow concentrtion. According to the dt, coting with the hrdness HV = 367 kg/mm 2 ws otined t I d = 8 A. Dt of the element nlysis 6 Fig. 5. Curves of indenter loding nd unloding Figure 6 shows the results of investigtion of dhesion strength of the deposited cotings in the form of coustic emission signl depending on loding nd indenter penetrtion depth. The presented dt confirm tht delmintion of the TiN coting deposited y conventionl technology egins t loding equl to.81 N. Surfce imge ner the indenter trck (Fig. 6а) shows tht the structure is porous, which revels high inner tensions in the mteril.
Orl Session Signl level, % Signl level, % Signl level, % 3 1 3 1 2 4 6 8 2 4 6 8 3 1 2 4 6 8 c Fig. 6. Chnge in coustic emission signl depending on penetrtion depth nd indenter loding, nd coting surfce imge ner the indenter trck: TiN without PF, TiN with PF, c (TiAl)N 7 When we use comined method of TiN coting deposition, criticl loding, t which coting delmintion egins, increses up to 1.17 N, which confirms increse in coting dhesion strength y 7%. For this cse we used high intensity comined ion clening, surfce heting nd ctivtion, formtion of thick trnsition lyer etween the sustrte nd coting, nd ion ssisted coting deposition. A complex of these fctors llowed form (TiAl)N coting from dc VAD plsm; coting delmintion ws oserved t criticl loding of 1.13 N. For this cse, crcking lines chrcteristic of mterils with high level of tension re sent ner the indenter trck (Fig. 6,с). In ws experimentlly found out tht with the increse in U in the rnge of 1 75 V we oserved increse in dhesion strength of TiN cotings y %. The highest vlues of dhesion strength were registered in the rnge of 1 25 V. The effect cn e ttriuted to decrese in compressing residul tensions resulting from increse in temperture, rdition tretment of the surfce, increse in formed phse sizes, etc. Figure 7 shows the results of investigtion of friction coefficient of TiN nd (TiAl)N cotings. The dt confirm tht if we deposit TiN coting onto steel P6M5, surfce friction coefficient decreses y 2.5 times with nd without PF. At the first stge of testing we oserved shrp increse in friction coefficient, which cn e explined y ruing of smples ecuse of surfce roughness the sme ws noticed for TiN cotings deposited with PF (curve 3). Due to low roughness, the effect of smple ruing is sent t the initil stge, nd more dense nd homogeneous coting structure cuses dditionl decrese in friction coefficient y %. Friction coefficient,8,7,6,5,4,3 TiN with PF TiN without PF TiAlN with PF,2 5 1 15 25 3 Lps, x1 3 Fig. 7. Chnge in friction coefficient depending on numer of rottions Figure 8 shows influence of surfce morphology onto wer resistnce of deposited cotings. 6 5 4 3 2 1 25 V 75 V 5 V 1 V (TiAl)N TiN with removl of wer wste TiN without removl of wer wste Without PF,,2,4,6,8 1, Wer resistnce Fig. 8. Wer resistnce of TiN nd (TiAl)N cotings depending on deposition regimes The digrm is normlized y unit with respect to wer intensity of steel P6M5 initil smple. The presented dt show tht TiN cotings deposited using the conventionl technology re chrcterized y doule increse in wer resistnce. At the sme time, use of PF llows dditionlly increse steel wer resistnce y 5 times. The dt otined on wer intensity
without removl of wer wste show tht presence of wer wste in the indenter trck, lter used s n rsive, result in shrp increse in wer intensity. However, for this cse wer-resistnce decreses 4 times compred to initil stte. Moreover, we didn t notice ny dependence of coting wer resistnce on smple is potentil. 4. Technologicl Applictions of the Method nd Its Future Perspectives The presented comined regime of surfce tretment with dc VAD gseous nd microprticle-free metl plsm under formtion of surfce negtive potentil llows effectively clen nd ctivte the surfce, including use of metl plsm, form diffusion trnsition lyers etween the sustrte nd coting, plsticize coting mterils, deposit homogeneous TiN nd (TiAl)N cotings with good exploittion properties. Experiments on comined use of the PINK plsm genertor nd VAE reveled tht t the expense of effective ioniztion of the rective gs one cn decrese chmer pressure for deposition of composite cotings, increse coting deposition rte nd increse coting dhesion strength t lower condenstion tempertures compred to tempertures for the conventionl method of coting deposition. Prcticl ppliction of the ove-mentioned regimes of ion nd plsm mteril tretment ws crried out t prominent RF tools plnt Tomsky Instrument. For this cse TiN nd (TiAl)N cotings were deposited onto metl-cutting tools. Upgrde of technologicl equipment for ion nd plsm coting deposition with gseous plsm genertors of PINK-type nd PFs llowed improve qulity of produced rticles, expnd nomenclture in the field of ppliction of produced items, stimulte development nd introduction of new types of cotings. E.g., production of rticles deposited with (TiAl)N cotings llowed oth increse wer resistnt chrcteristics nd offered perspectives of coting ppliction for luminium lloy rticles; het resistnt properties of (TiAl)N cotings permitted void tool cooling with liquids nd significntly increse processing velocity. Comined ppliction of the PINK genertor nd PF llows generte high-qulity cotings using dc VAD plsm on rticles with the operting surfce re equl to the size of microprticle frction.1 1 mm. Perspectives of ppliction of dc VAD plsm for deposition of Al 2 O 3, TiC, DLC, etc. cotings, which otherwise cnnot e deposited using conventionl VAE since the size of microprticle frction for them is more thn 1 µ, re reveled. References [1] V.А. Brvinok, Control of stress stte nd chrcteristics of plsm cotings, Moscow, Mchine uilding, 199, p. 384. [2] H.G. Prengel, A.T. Snthnm, R.M. Penich, P.S. Jindl, K.H. Wendt, Surf. Cot. Technol. 94 95 597 (1997). [3] A.I. Rychikov, I.B. Stepnov, Ptent RU 97868 C1, 1998. [4] A.I. Rychikov, I.B. Stepnov, Rev. Sci. Instrum. 69, 893 (1998). [5] D.P. Borisov, N.N. Kovl, P.M. Shnin, Izv. Vuzov. Physics, 37, iss. 3, 115 (1994). [6] I.M. Gonchrenko, S.V. Grigoriev, I.V. Loptin, N.N. Kovl, P.M. Schnin, A.A. Tukhftullin, Yu.F. Ivnov, N.V. Strumilov, Surfce nd Cotings Technology 169 17, 419 (3). [7] I.B. Stepnov, S.V. Dektyrev, A.I. Rychikov, I.A. Rychikov, D.O. Sivin, I.A. Shulepov, in: Proc. 6 th Int. Conf. on Modifiction of Mterils with Prticle Bems nd Plsm Flows, 2, pp. 649 653. [8] S.V. Fortun, Yu.P. Shrkeev, I.A. Shulepov, I.B. Stepnov, in: Proc. 6 th Int. Conf. on Modifiction of Mterils with Prticle Bems nd Plsm Flows, 2, pp. 547 551. [9] P.M. Shnin, N.N. Kovl, A.V. Kozyrev, I.M. Gonchrenko, J. Lngner, nd S.V. Grigoriev, in: Proc. 5 th Int. Conf. on Modifiction of Mterils with Prticle Bems nd Plsm Flows,, pp. 438 441. 8