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Vol. 2(1)

Uzbek Journal of Physics 2000

PP. 100-106

VACUUM ARC DEPOSITION OF DECORATIVE AND PROTECTIVE COATINGS ON THE LARGE-AREA GLASS AND STEEL SUBSTRATES
B. B. STRAUMAL1, 2, N. F. VERSHININ1, 2, O.V.GRIBKOVA3, A. V. KAZAKEVICH3, A. CANTARERO4, J. CAMACHO4, A. SANCHEZ5 (1 I. V. T. Lt d., P.O. Box 47, RU-109 18 0 Mo scow, Russ ia; 2 In s tit ut e o f Soli d S t at e P h ys i cs , C hernogo lo vk a, 14 24 32 M os co w Dist ri ct, Ru ssi a; 3 M oscow State Institute of Steel and Alloys, 117049 Moscow, Russ ia; 4 Materials Science Institute, University of Valencia, 46071 Valencia, Spain, 5 Universidad Politecnica de Valencia, 46022 Valencia, Spain)
An i n d u str ia l i n sta l la ti o n fo r vac uum a rc de po si t io n i s p r ese nt ed. I t s po te nt ia l i n t h e fi eld o f d eco ra ti v e co atin g s fo r lar g e area g lass and st ee l sh ee ts is d e mo n s tr at ed . Par t ic u larly it is p o ssib le to d epo sit pa t ter ned co at i ngs t h ro ugh a t e xt i le po l yme r i c ma sk. T iN, T iO2 and mu tilaye r T i N/T i O 2 co atin g s h a ve b een ch aracterized. Th e depth p r ofilin g wa s ma d e with th e aid of Au g e r electron s p ec tro s cop y. T h e corr os io n r es i s ta n ce o f T iN co at i ngs i s hi gher t h a n t h e corr o sio n r e si s ta n ce o f TiO2 . T he co rro sio n re si st a n ce o f vac uum a rc dep o si te d T iN coati ngs o n gla s s p ro ve s t o b e hi gher th an th at of TiN co atin g s p r o d uc ed by direct curr en t reactive sp u t terin g an d plas ma as si s ted ch emical va po ur de po si t io n. Pa tt er ne d T iN coa t i ngs do no t sho w a n y si gns o f a n a cc el er at ed co rro sio n a lo n g th e b o rder b e tween the co at ed and u nco ated g las s.

INTRODUCTION Vacuum a r c deposition is an ef fective and environm ental friendl y tec hnique for the production of de coration co ating s on archite ctural g l ass and ste e l. This robust and inex pensive process allows to produc e coat ed materials fo r building and construction which are che a p enough to be able to compete with materials prep are d in a traditional m e t a l l u rg i c al wa y . P a rt i c ul arl y , i n t h e l a st ye a r s st ai nl ess st eel st ri ps and rods coat ed with TiN in S ONG Lt d. we re us ed b y building comp anies in Moscow for th e r e building of th e Ca the d ra l of Chr i st The Sa viour ( 2 m lon g e l e m e n ts f o r the c h a i ns fix i ng the crosses on the domes ), for the construction of the monument fo r Empero r Peter the Gr eat and of th e new roof fo r the Moscow Lu z hniki Ol ym pic Stadion (altogether about 2000 m 2 , 1x 2 m coated strips are used) and for the r econstru c tion of the roof of the Gre a t Kremlin Palac e (about 200 m lon g de corative gr atin g , made of laser pattern ed and TiN coated 1x 2 m strips). Vacuum a r c pro cess allows on e to deposit ver y uniform co ating s on the thr ee-dimension a l parts havin g complicat ed form. Especiall y important a r e the possibilities to produce the patte rned coatin g s and coat i n g s wi t h an y i n t e r f e r en ce col our (l i k e red, pu rpl e , g r een, ye l l o w et c.) on l a r g ea r e a substra t e s . This a llows in pa r tic ular to ha ve th e sc ra tc h a nd w e a r r e sista n t drawin g s for the d eco rative and advertisement pu rposes or appl y th e unusual colours for g l az ing instead o f " o ld -fashioned " bro w n windows.

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E X P E RIME NT AL OUT L I NE The industrial scale set - up " N ikol a y " us ed for th e deposition of coatin g s on the l a rge- are a ar chi t ect ur al g l asses and st e e l st ri ps has t h e fol l o wi n g cha r act eri s t i c s: si z e 6000 в 3000 в 3000 mm, mass 15500 kg , max imum power consumed 75 kW , ultimate vacuum 5 в 10 ­4 Pa, max imu m siz e of substrates 2100 в 1300 в 8 mm, output capacit y 30 sheets 2100 в 1300 в 5 mm in a 8 h c y c l e, up to 1000 m 2 /month. A standard proc edur e for deco rat i v e co at i n g i n cl udes t h re e st eps. The st ri p be fore b e i n g l o aded i n t o t h e ma c h ine is pr ec le a n e d using hot distille d wa te r . Afte r prec le a n in g , the shee ts a r e mounted on metallic frames and plac ed in the machine v acuum ch amber. E ach f r ame contains two sheets, mounted ba ck to back. Th e fr ame is inserted into a slot (15 slots are av ailable) and allowed to move indep e ndentl y inside the ma chine, in orde r to recei v e di ffe rent t r e a t m e nt oper a t i ons. The di spl acem ent vel o ci t y o f t h e f r am e i s m oni t o red and can b e cont rol l e d. E ach f r am e r e c e i v es i n t u rn a cl eani n g t r e a t m e nt followed immediatel y b y a co ating in ord e r to pre v ent re contamination. The complet e treatment involves one r e turn of the frame for cl eanin g and another r e turn fo r coatin g . Cleaning is per f ormed usin g a l a r g e apertur e Hall cu rrent acc eler ator, providin g hig h ener g e tic ions whi c h impact and sputter th e substrate sur f ac e. The de scription of the Hal l curr ent ac cel er at or and i t s pe rform an ces i s g i ven el se wher e [ 1 ] . A Hal l current acc el erat o r i s pl aced on each si de of t h e m a chi n e i n orde r t o cl ean t h e t w o sheet s of the frame in on e shot. The hi g h po wer p r ovi des a suf f i c i e nt cl e a ni ng o f bot h surf aces i n an y circumstanc e s. The coa ting in the industrial set-up is perfo rmed using four ci rcular targets of 200 mm diameter. Th re e sourc e s are plac ed on ea ch side of the installation. Onl y two sour ces a r e norm a ll y used du rin g the deposition. A re active gas (ox y gen) is introduced at 0.05 Pa if ox ide coatin g is to be formed. TiN c o atin g is obtained b y introducing nitro g en at a pr essure o f about 0.05 Pa. The arc gener a tion is continuous and random. As microd r oplets ar e eje c ted at small angles [ 2 ] with respect to the tar g et surfac e , this confi g uration provides shi e lding and enables to inc r ease the ch ar g e d particles component of th e beam. As for cl eanin g , the thickness of th e deposited la y e r is c ontr o lle d b y v a r ying the tr a n sla tion spee d of the f r a me . Gla ss, me ta l a nd pla s tic sheet s have b een suc cessful l y co at ed wi t h Ti , Ti N, Ti O 2 a nd multila y e rs of TiN/TiO 2 . W h en decorative p a tterns hav e to be produ ced, li g h t n y lon p a tterned sh eets ar e used to provide masking . Various colou r s can b e produc ed dep e nding on the g a s and deposition parameters us ed. I n this stud y Ti, TiN, TiO 2 and Ti N/TiO 2 coat ed si l i cat e g l ass sam p l e s w e r e cut from l a r g e g l ass she e t s and an al y s ed re gardi n g surf ac e morpholog y, composition and co rrosion resistanc e . The composition depth profile of TiN/TiO 2 co at ed si l i cat e g l ass w a s m a de b y Auger ele c tron spe c troscop y ( A ES). The spe c imens we re mounted in the load ers of the spe c t r o me ter c a r r ouse l holder a nd se qu e n tia ll y r o ta te d into the a n a l y s is position. The anal ys i s was car ri ed out wi t h t h e ex ci t a t i on beam norm a l t o t h e speci m e ns. Th e spectra w e re t a ken durin g ar g on ion sputtering which produ ced a relativel y clean surfac e of the s a mple under stud y without bakin g the s y stem. The etchin g rate was
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VACUUM ARC DEPOSITION OF DECORATIVE AND PROTECTIVE COATINGS ...

consi d erabl y f a st er t h an t h e adsorpt i on rat e of t h e a c t i v e resi du al gases. Th e Au g e r spectra w e re m easur ed on a PH I - 551 spectrom e ter with a double - pass c y lindric al m i rror anal yz er. Th e base p r essur e was l e ss t h an 2 в 10 ­8 P a . The spe c t r a wer e ex ci t e d b y an el ect ron b eam wi t h an ener g y o f 3 keV a nd a cu rrent o f 8 µ A t h rou g h the sample. The pe ak-to-pe ak modulation was 3V. Th e sputterin g was accomplished usin g a 5 keV A r + ion beam. An ion g un was mounted to g i ve a b eam inciden ce an g l e of 70 o , a nd in or de r to minimize possible c r a t e r e f fe c t s, it wa s r a st e r e d. Th e pr e ssu r e of a r g o n during sputterin g w a s 3 в 10 ­ 3 Pa . The sputte r ra te s wer e de t e r mine d to be 25 nm/min r e la tive to SiO 2 . The corrosion b e haviour of both TiN and TiO 2 coat i n g s on si l i cat e gl ass w a s chara c t e ri z e d. The st andard acc el er at ed t e st s on at m o spheri c corrosi on w e re ca rri ed out accordin g to the Russian standa rds RS T 9.012, 9.017 and 9.020 (temper a ture 22­ 25°C, humidit y 96­98%, no w a ter condensation, unde r influenc e of gas e ous chlorides, ammoniac and SO 2 ). The acc eler ated test in 3.5% NaCl solution at 22­25 °C under both f u ll a nd pa r tia l imme r s ion wa s a l so ca r r i e d out. B o th unif o r m a nd m a skdeposi t e d Ti N coat i n g s we re st udi ed be cause on t h e board er bet w een coat ed and uncoated g l ass the TiN/ g l ass inter f ac e is ex posed to the corrosion medium. The polariz ation behaviour was me asured potentiod y namic all y with the a i d of a potentiostatic apparatus P I -50 - 1/PR8. All potential values are g i ven v e rsus the Ag /A g C l e l ec tr ode ( E Ag / A g C l = 0 cor r esponds to ­ 200 mV in the h y dro g en elect rode scal e). Th e scanni n g ra t e w a s 1 m V s ­1 . The polariz ation was chan g e d from ­ 0.8 V to

Fig. 1. Patterned TiN/TiO2 coating vacuum arc deposited on silicate glass through polymeric mask (left-hand sample) and uniform TiN coating deposited without mask (right-hand sample). 102


B. B. STRAUMAL, N. F. VERSHININ, O.V.GRIBKOVA, A. V. KAZAKEVICH...

80

Concentration, at.%

60

Concentration, at.%

C Ti O Si

80

60

40

40

C Ti O Si

20

20

0 0 20 40 60 80

0

Sputter time, min
Fig. 2 . AE S sp ec tr a fo r the Ti co atin g o n silicate g lass.

0

20

Sputter time, min

40

60

80

Fig. 3 . AE S sp ec tr a fo r t he T iO2 coat i ng o n s ilicate g l as s.

+ 1.5 V. Befor e potentiod ynamic measu r ements, the corrosion potential E c wa s monitored for 0.5 h. The me asurem ents wer e ca rried out in the el ectrol y tes of 3.0 % NaCl solution and 3.0% NaCl + 3.0% NH 4 Cl solution with pH = 6. The co rre ction of the pH of the solutions was ca rried out b y addition of 0.05 mole of N H 4 OH (to the solutions containing NH 4 Cl) and b y addition of 0.05 mole of Na OH (to the solutions without NH 4 Cl). The pH value of a solution was controlled b y a pH-met er " p H - 121 " . The solution wa s pr e p ar e d fr om r eag e n t- gra d e c h e mic a l s a nd distille d wa t e r . The a r ea ex posed to solution was 1 cm 2 , the rest surfac e of the samples w a s isolated b y a varnish la y e r. Th e test temper ature wa s 22­25 °C. RE S U L T S AND DIS CUS S I ON The photographs of the p a tterned Ti N/TiO 2 coatin g deposited on silicate g l ass throug h pol y m eri c mask (left - hand sample ) together with uniform coatin g (ri g h t-han d sample) ar e shown in F i g . 1. Th e depth con centration pro f ile obtained f r om the Au g e r spect ra fo r Ti and Ti O 2 co at i n g s on si l i cat e g l ass ar e shown i n Fi g . 2 and 3 respectivel y. Th e peaks char acte r istic for titanium, ox y g en, c a rbon and silicon w e re anal yz ed. After about 3 min of sputtering , the surf ace contamination of c a rbon and ox yg e n dis a ppe ar f r o m the sp e c t r a . Th e inc r e a s in g c o n c e n tra tion of silic on ma r k s the tr a n sition f r o m the c o a tin g to substr a t e . Th e ox y g e n c ont e n t in the Ti c o a tin g ste a d il y

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VACUUM ARC DEPOSITION OF DECORATIVE AND PROTECTIVE COATINGS ...

100

10
ic , mA/cm

Ti TiN

ic , mA/cm

2

10

Ti TiO 2 (red) TiN TiO2 (green)

2

1 TiO2 (red) TiO 2 ( green)

1

0.1

0.1

0.01
0.01 -0.8 0 E, V
Fig. 4 . Th e dep e n d e n ce of co rro si on curr en t i c on t he p o la ri s at io n vo lt a g e E in the 3 .0 at.% Na Cl so lu tio n at pH=6 .

0.8

1.6

-0.8 -0.4

0

0.4 E, V

0.8

1.2

Fig. 5 . Th e dep e n d e n ce of co rro si on curr en t i c on t h e po l ari sa ti on vo l tag e E in the 3 . 0 at.% NaC l + 3 .0 at . % NH4 Cl so lu tio n at p H=6 .

i n creas es t o wards t h e subst r at e. The ox y g e n cont ent i n t h e Ti O 2 c o a ting r e ma ins unc ha n g e d e x c e p t the thin Ti- r i c h la y e r c l ose to the g l a ss substr a t e . Qua n tita tive a n a l ys is r e vea l s tha t the Ti to O r a tio in the TiO 2 co ating is about 1.95 b e ing v e r y close to the stoichimetrical one. Th e ca rbon con centration is ne arl y constant in the whole c o a tin g ( c los e to ze r o in the TiO 2 and slig htl y below 20 at. % in Ti). At the coating / substrat e interf ace th e ox y g en and silicon co ntent climb up as the titanium content slig htl y falls down. After 12 months of tests in atmospheric corrosion with conditions which correspond to the most a ggressive a r t of the industrial atmospher e , no chan ges of mass and appe aran ce i n t h e ch ar act eri z ed sam p l e s w a s m oni t o red. I t dem onst r at es t h e hi g h resi st ance a g ai nst at m o spheri c corrosi on of t h e cha r act eri z ed Ti N and Ti O 2 c o a ting s on silicate g l ass. Th e cor r osion tests car ried out in a NaCl solution during 12 months also showed no chan g e s in the mass and appea r anc e of the s a mples both b y full imme r s ion a nd b y p a r tia l imme r s ion in the zone of c onta c t b e twe e n solution a nd a i r . This hig h cor r osion resistanc e is compar able with the prope rties of va cuum ar c deposited TiN coatin g s on steel and b r ass substrates [ 3 ] . The mask-deposited TiN coat i n g s do not show a n y si g n s o f ac cel e r at ed corrosi on al on g t h e bo rder b e t w e e n coat ed and un coat ed g l ass. The data of electrochemical tests are displayed in Fig. 4 (NaCl solution) and Fig. 5 (NaCl + NH4Cl solution) both at pH = 6. The dependence of corrosion current ic on the polarisation voltage E is shown for Ti, TiN coatings and for two different TiO2 coatings of various thickness having red and green colours. For both TiN and TiO2 no active peaks are present and the coatings are in the self-passivated state. For N a C l s o l u t i o n E c (Ti) = ­ 0.22 V, E c (Ti N ) =
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0.05 V, E c (Ti O 2 , red ) = ­ 0.1 V and E c (Ti O 2 , g r een) = ­ 0.14 V. F o r NaCl + NH 4 Cl solution E c (Ti) = ­ 0.26 V, E c (TiN) = 0.15 V, E c (Ti O 2 , red) = ­ 0.1 V and E c (Ti O 2 , g r een) = ­ 0.05 V. This data sho w that the cor r osion resistanc e of TiN is much hi g h e r t h an t h at of Ti and Ti O 2 in both solutions studied. F u rthermore, the TiO 2 c o a ting is more corr osion resistant than pure Ti. Neve rtheless, E c in a ll ca se s re ma ins mor e positive tha n the r e duc tion pote n tia l f o r h y d r o g e n. This re ve a l s tha t the c o r r o sion process fo r all coatin g s studied can proc eed onl y with ox y g en depolariz ation. I t can be seen in F i g s . 4 and 5 that both c a thodic and an odic proc esses a r e less pronoun ced on t h e surfac e of Ti O 2 in c o mp a r ison with TiN. I n the pre s e n ce of N H 4 Cl i a for Ti N decre a ses in compa r ison to NaCl solution. i a for Ti and Ti O 2 r e ma ins on the sa me level, but the differ e nc e for TiO 2 co at i n g s o f di ffe rent t h i c kness i n cr eas e. I t i s al so important to mention that at voltag e s of a nodic polariz ation of TiO 2 osc illa tions of i a ta ke pla c e . The s e os c illa tions me a n tha t the loc a l re pe a t e d c o rr osion a tta c k of th e coat i n g su rfa ce l a ye r pro ceeds and t h at t h e surf ac e i s repe at edl y a c t i v at ed. Numerous pape rs report d a ta on the electro chemical p r operties of TiN deposited on metallic substrates like tool steel [ 3­9] . The corrosion proc ess of Ti N/ st eel i s rat h er com p l i c at ed and i n cl ud es, t oget h er wi t h co rrosi on of Ti N, t h e corrosion of the ste e l substrate. I t c a n be controlled b y the pen e tration of the corrosi on a g ent s bot h al ong t h e i n t e rfa ce b e t w een t h e coat i n g and subst r at e and throug h d e fe cts in the coatin g . I n ord e r to discuss cor r e c tl y our results, we should use the data on ele c troch e mical prope rties of TiN deposited on g l ass b y r e active d.c. sputtering [ 9 ] and on Al 2 O 3 b y P A C VD [ 5 ] . Both g l ass and Al 2 O 3 subst r at es are i n e r t from t h e cor r osi on poi nt of vi ew. Ther efor e, t h ese d a t a ch ara c t e ri z e t h e i n t r i n si c properties of TiN rather th an a combination of corrosion pro cesses o f both substrate and coatin g . The v a lues of co rrosion cu rrent densit y , i c (est abl i s hed as t h e cu rrent densit y on the c a thodic polariz ation curv e cor r espondin g to the E c ) r e po rted in [ 5, 9] are of th e same ord e r of m a g n itude as in our wo rk. The co rrosion potential E c of TiN in a NaCl solution with pH = 6 in our work is about 0.09 mV more positive than E c r e por te d in [8] f o r ne a r l y the s a me e l ec tr oc h e mic a l c onditions. I n [5] the da ta a r e g i ven f o r pH = 1 ( E c = ­ 0.23 V, re calculat e d for the Ag /AgC l el ectrod e ) and pH = 12 ( E c = ­ 0.33 V) which is much lower th an both values obtained in this work. Th e pronounced anodic peak is p r esent in all potentiod y namic cu rves pre s ented in [ 9 ] . In t h i s work coat i n g s are i n t h e s e l f-p assi vat e d st at e. The r efo r e, t h e corrosi on r e si st ance of TiN deposited b y the va cuum ar c proc ess is definitel y hi g h er than that of TiN coating s d e posited on silicate g l ass substrates b y rea c tive d.c. sputterin g [ 9 ] and on Al 2 O 3 substrates b y PACVD [ 5 ] . A c knowle d gem e nt s . The financial support of Ge ne ralidad Va lenci a na, Is o p r ess-In t e r Prog r a mme of the Russian Ministr y o f Scienc e and T echnolo g y; the Pro g ramme for cooperation betw een Sw eden and the forme r Soviet Union of the Roy a l Swedish Academ y o f Sciences a nd Copernicus n e twork ( c ontra ct ERB I C 15 CT98 0815) is heartil y acknowl e d g ed.
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REFERENCES 1. 2. 3. 4. 5. 6. 7. 8. 9. N. Vershinin, B. Straumal, K. Filonov, R. Dimitriou, W. Gust, M. Benmalek, Thin Solid Films 351 (1999) 190. J. E. Daadler, J. Phys. D9 (1976) 2379. A. K. Vershina, I. A. Bel'chin, A. A. Pitel'ko, S. D. Izotova, Fiz. Chim. Obr. Mat. No. 5 (1990) 93 (in Russian). B. In, S. P. Kim, Y. I. Kim, W. W. Kim, I. H. Kuk, S. S. Chun, W. J. Lee, J. Nucl. Mat. 211 (1994) 223. E. Lunarska, J. Michalsky, J. Mat. Sci. 30 (1995) 4125. W. Brandl, C. Gendig, Thin Solid Films 290­291 (1996) 343. C. B. In, S. P. Kim, J. S. Chun, J. Mat. Sci. 29 (1994) 1818. E. Lunarska, S. Al Ghanem, phys. stat. sol. (a) 145 (1994) 587. Y. Massiani, A. Medjahed, P. Gravier, L. ArgХme, L. Fedrizzi, Thin Solid Films 191 (1990) 305.

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