Effect of crystallographic orientation on erosion characteristics of arc evaporation titanium nitride coating

Surface and Coatings Technology, 33 (1987) 169

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EFFECT OF CRYSTALLOGRAPHIC ORIENTATION ON EROSION CHARACTERISTICS OF ARC EVAPORATION TITANIUM NITRIDE COATING* J. A. SUE and H. H. TROUE

Union Carbide Corporation, 1500 Polco Street, Indianapolis, IN 46224 (U.S.A.) (Received March 9, 1987)

Summary

Recent development of TiN coatings specifically for erosion protection has focused on better process control as well as crystallographic orientation. The erosion behavior of TiN coatings, which were produced by the arc evaporation process, was evaluated using 27 ,.tm angular alumina particles at a velocity of 91 m s1. The eroded surfaces were examined in a scanning electron microscope, and erosion mechanisms in response to the oblique and normal impacts were characterized. The erosion characteristics of various TiN coatings are presented. The variation of surface morphology, microstructure, hardness and erosion characteristics of the coating with crystallographic orientation is also discussed.

1. Introduction TiN coating has been successfully used for machining tools and forming tools in the manufacturing industries. Recently, there has been an increasing interest in the use of this coating for microelectronics, aerospace and nuclear energy applications. Many chemical vapor deposition (CVD) [1, 2] and physical vapor deposition (PVD) [3 7] processes have been developed to produce TiN coatings for these applications. However, the physical and mechanical properties of TiN coatings are highly dependent on their deposition processes [8]. In general, for deposition temperatures below 700 °C and for precision components, the PVD process is preferable, whereas above 700 °Cthe CVD process may give better results in some applications. Many papers have reported on PVD TiN coatings deposited with sputtering, ion plating, activated reactive evaporation (ARE) or other processes. Far less information is available on PVD arc evaporation TiN coatings, even though the process has become commercial practice. -

*Paper presented at the 14th International Conference on Metallurgical Coatings, San Diego, CA, U.S.A., March 23 - 27, 1987. 0257-8972/87/$3.50

© Elsevier

Sequoia/Printed in The Netherlands

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The properties of TiN most often evaluated are hardness [9 12], color [13 20], structure [4, 8, 9, 16, 21 23], composition [16, 24 26], lattice parameter [11, 17, 18, 27, 28], internal stress [29 31], electrical resistivity [27, 28, 32, 33], frictional wear [14, 34] and corrosion [35-37]. Very little is known about erosive wear characteristics. Nonetheless, the potential use of TiN as an erosion-resistant coating is well recognized. Furthermore, preferred orientations are generally observed in PVD and CVD TiN coatings. Although the importance of preferred orientation to the tribological performance of the coating has recently been identified [38] -

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relatively little has been published about the effect of crystallographic orientation on wear characteristics, particularly on erosion behavior. In this paper, the variation of structure, surface morphology and hardness with crystallographic orientation for PVD arc evaporation TiN

coatings is reported. The relation between erosion behavior and crystallographic orientation of PVD arc evaporation TiN is characterized and erosion mechanisms are discussed. 2. Experimental procedure TiN coatings were prepared with a PVD arc evaporation process using both conventional and modified (Union Carbide) arc evaporation apparatuses. The principles of these arc evaporation processes have been described elsewhere [39 -43]. The substrate to be coated was first mechanically polished and then

ultrasonically cleaned in a bath of methanol. Before deposition, the chamber was evacuated to a pressure below 7 X iO~ Pa. The chamber was then backfilled with argon (purity, 99.99%) to a pressure of 0.7 Pa and the substrate was sputtered to remove surface contaminants using a negative bias of 1 kV d.c. Subsequently, the coating deposition was carried out in an atmosphere of nitrogen (purity, 99.998%). The depositing titanium metal was evaporated from a titanium cathode by a high current—low voltage d.c. arc discharge. The resulting positive ions of titanium and nitrogen were accelerated toward and then deposited on the substrate, to which a negative bias of —100 to —200 V d.c. was applied. The deposition temperature, determined using an optical pyrometer, was between 450 and 700 °Cand the deposition rate was from 0.05 to 0.12 jim min1. The thickness of the coating varied from 25 to 40 jim. X-ray diffraction techniques using Cu Ka radiation were used to de-

termine the crystallographic orientation and phases in the coating. The (111) X-ray line of silicon powder was used as the standard to calibrate the instrument. The mjcrostructure of both the surface and the cross-section of the coatings and their erosion scars after test were studied in an optical microscope and a scanning electron microscope (SEM). The coating for the crosssectional microstructure study was mechanically polished through 120, 240,

171

320 and 600 SiC papers, followed by 1 jim diamond paste. The hardnesses of the coatings were measured using a Vickers hardness tester with a load of 300 g for a loading time of 15 s. At least 15 measurements were taken for each sample. The diagonal length of indentations was measured on optical micrographs at 1000 times magnification and then converted to the Vickers hardness number. Samples for the alumina erosion test were coated with TiN on Ti—6Al— 4V blocks, 1.9 cm X 6.4 cm X 1.2 cm. The substrate was ground to a surface finish of 0.13 0.38 jim r.m.s. before coating. The erosion resistance of the coatings was determined by impacting with angular Al203 particles (nominal particle size of 27 jim) at impact angles from 20°to 90°.The feed rate and velocity of the particles were 1.15 1.20 g min’ and 91 m s’ respectively. The distance from the injection nozzle to the coating surface was 1 or 1.2 cm. The erosion rate was measured in terms of the penetration depth (in micrometers) in the coating per gram of incident particles. The test set up was based on ASTM G76-83 guidelines [44]. -

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3. Results and discusssion 3.1. Preferred crystallographic orientation

TiN coatings with preferred orientations have been produced in both PVD and CVD processes. Sun et al. [141 have reported that TiN films prepared by ARE exhibit preferred orientations in the (111) and (200) planes or in (200) and (220) planes. Using an ion plating process, Kobayashi and Doi [45] have shown that (111) or (220) preferred orientation of TiN coatings can be obtained, depending on the accelerating voltage and reactive gas pressure during deposition. Matthews and Teer [4] have shown that the current density of the sample and the chamber pressure have marked effects on the preferred orientation of TiN, (111) or (200). For the CVD process, the preferred orientation of TiN coating changes from (220) to (111) when the gas pressure increases from 3.3 X 102 to 4.7 X 102 Pa and above [45]. Kim and Chun [46] have observed that the (220) preferred orientation is increased with an increase in deposition temperature. Thus, in any PVD or CVD process, a deposited coating will probably have a preferred orientation to some degree. Although the reason for the phenomenon of preferred orientation has not yet been fully identified, the degree of preferred orientation of deposited coatings is clearly dependent on the process and deposition parameters. The PVD arc evaporation TiN coatings exhibited very much higher preferred orientation in (111) than did the ASTM powder diffraction of TiN [47]. Quantitatively, the (111) intensity value of X-ray diffraction can be used to distinguish differences among these coatings. However, the (111) intensity value of the coating alone has no physical significance. Furthermore, the (111) intensity value of the TiN coating is sensitive to instrument conditions and coating thickness when less than about 14 jim. Therefore,

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the intensity ratio of (111) to (200) diffraction was introduced to rank quantitatively the degree of (111) preferred orientation of the coating. The 1(111)/1(200) value represents the overall intrinsic property of the coating, in that a higher 1(111)/1(200) value simply indicates a higher volume fraction of TiN crystallite oriented in the (111) plane, which is parallel to the coated surface of the substrate. The 1(111)/1(200) values of the PVD arc evaporation TiN coatings varied from 3 to 2000 or greater. TiN coatings with 1(111)/1(200) values less than and greater than 50 were produced with a conventional and a modified (Union Carbide) arc evaporation apparatus respectively. A quantitative comparison of the published data [45, 46, 48, 49] on degree of (111) preferred orientation among TiN coatings prepared by these and other processes is given in Table 1. Clearly, the modified (Union Carbide) arc evaporation process is superior to others in producing a highly (111) oriented TiN coating. TABLE 1 I(111)/I(200) values of TiN coatings

Process

1(111)11(200)

Modified arc evaporation (Union Carbide) Conventional arc evaporation CVDa CVDb Ion plating’~’° Ion-stimulated sorption’~

50 to over 2000 1 - 40 0.4 - 0.9 1.2-15 0.3 - 4.8 0.5 - 2

aReference bReference C Reference dReference

45. 46. 48. 48.

3.2. Surface morphology and cross-sectional microstructure SEM examinations reveal typical surface structures of TiN coatings consisting of a greater number of rounded concave depressions with a few inclusions, which resulted from cathode spitting during evaporation (Fig. 1). The number of inclusions decreased markedly with increasing 1(111)/1(200) value. The surface features of the coatings with an 1(111)11(200) value less than about 50 exhibited typical characteristics of conventional arc evaporation TiN coatings reported previously [50, 51]. The formation and the shape of the depressions are not yet fully understood. They may be related to the number of impinging ions and neutrals and their energy density and penetration depth. However, the size and number of depressions are clearly sensitive to deposition parameters. An experiment was carried out to evaluate variations in surface structure with substrate stand-off and deposition temperature. Five specimens were

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1~fl~ Fig. 1. Surface structure of TiN coating as a function of I(111)/I(200) value: (a) 1(111)1 1(200) = 78; (b)I(111)/I(200) = 220; (c) I(111)/1(200) = 960.

simultaneously coated with a coating stand-off varying from 20 to 51 cm at a deposition temperature from 630 °Cto less than 300 °C.The surface structure showed that the size and number of depressions decreased with increasing stand-off and with decreasing deposition temperature. Figures 2(a) (c) show the cross-sectional microstructures of a series of PVD arc evaporation TiN coatings as a function of their 1(111)11(200) -

[a inclusion

TiN TIN

_____________________________

C N~ Plate

Ti N

substrate

2Opm

Fig. 2. Variations of TiN coating structure with 1(111)/1(200) value: (a) 1(111)11(200) 78; (b) 1(111)/1(200) = 220; (c) 1(111)/1(200) = 960.

=

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values. The size and amount of porosity and titanium inclusions decreased with increasing values of 1(111)/1(200). This is consistent with the surface morphologies of TiN coatings observed in Fig. 1. Apparently, the microstructure of the coating strongly depends on its 1(111)/1(200) value. Therefore, in the PVD arc evaporation TiN coatings, the 1(111)/1(200) value may well represent an overall intrinsic property which also governs physical and mechanical properties of the coating. 3.3. Hardness A wide range of hardness values (HV) of TiN thin films, varying from 340 to over 3000 HV, have been reported [4,9, 11, 12, 14, 27]. This variation has been attributed primarily to the crystallographic orientation of TiN and/or the presence of the second phases in the coating, such as Ti2N. The hardness value of a TiN coating with a preferred orientation in the (200) plane is greater than that of a coating with a (111) preferred orientation [4], and maximum hardness is usually obtained in the coating containing a mixture of Ti2N and TiN phases [4, 11]. The hardnesses of PVD arc evaporation TiN coatings were measured on surfaces parallel to the substrate surface using a Vickers hardness tester. The coatings used for this measurement had thicknesses greater than 25 jim such that the ratio of coating thickness to indentation diagonal length exceeded the minimum ratio criterion [52, 53]. The variation in TiN coating hardness, plotted as a function of 1(111)/1(200) value, is shown in Fig. 3. The value of hardness increases with increasing 1(111)11(200) value from 2000 HV 0.3 for 1(111)11(200) 3 up to a maximum 2200 HV 0.3 at 1(111)/1(200) 40. This is probably because of a reduction in the amount and size of pores and inclusions in the coating. With a further increase in 1(111)/1(200) the hardPVD ARC EVAPORATION TIN COATINGS 2600

—

2400

-

I~

,,y~i~4~TmBULK.~..

1400

-

~11

10

100

1000

1(111) / 1(200) Fig. 3. Hardnesses of TiN coatings as a function of 1(111)/1(200) value.

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ness of the coating decreases to 1700 HV 0.3 for I(111)/I(200) = 960. This is probably related to effects of crystallographic structures as well as the internal stress of the coating. The hardnesses of TiN coatings, measured on the cross-sectional surface, varied from 1700 to 1800 HV 0.3 which is slightly lower than the bulk hardness value of TiN. 3.4. Erosion and crystallographic orientation The erosion rate of TiN coatings was measured at both 30°and 90° impingement angles. Irregularly shaped 27 jim alumina particles with sharp corners and edges and with a hardness of approximately 2000 HV were used. The distances from the injection nozzle to the target surface were 1.2 cm and 1.0 cm for impingement angles of 30°and 90°respectively. Logarithmic plots of erosion rate W~,vs. {1(111)/1(200)} for a number of TiN coatings are shown in Fig. 4 for both impingement angles. The linear relationship between W~ and lg {I( 111 )/I(200)} was obtained from linear regression analysis with a correlation coefficient of —0.9. Therefore, the

TIN COATING AL

2 03 EROSION 27 urn PARTICLE SIZE Si rn/s.c PARTICLE VELOCITY

10

100

1000

10,000

10

100

1000

10,000

10

1(111) / 1(200) Fig. 4. Plot of alumina erosion rate us. lg{I(111)/I(200)} at impingement angles of: (a) 900; (b) 3Q0

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erosion rates of TiN coatings to alumina erosion at 30°and 90°impingement angles are respectively W~.= 8.3

1.8 X lg{I(111)/I(200)}

—

and W~= 60.5

—

14.9 X lg{I(111)/I(200)}

where W~,is in micrometers per gram. The accuracy of alumina erosion of TiN coatings predicted with these two equations is within 30% and 40% respectively. SEM examinations of eroded surfaces were carried out on coatings with 1(111)11(200) values from 3 to 960. Figures 5 and 6 show qualitatively that surface damage of TiN decreases with increasing 1(111)/1(200) value for 90° and 30° impacts respectively. At normal impact, fragments of Al203 less than 5 jim in size, caused by the fragmentation of impacting particles, were occasionally observed embedded in the eroded surfaces. In the TiN coating with an 1(111)/1(200) value of 3, the predominant features of the impact crater were primarily formed by chipping fracture and some degree of plastic deformation from direct impact (Fig. 5(a)). The chipping scars are probably caused by the lateral cracks from the impacts of angular particles. As the value of 1(111)/1(200) inc!eases, the degree of chipping and fracture is noticeably reduced. For coatings with 1(111)/1(200) values of 78, surface damage consisted of scars of microchipping, shallow craters and steps resulting from the detachment of thin platelets (Fig. 5(b)). The thin platelets probably resulted from the overlapping of impact craters and/or the delami-

Fig. 5. Scanning electron micrographs of eroded surfaces of TiN coatings formed by alumina erosion at 90° impingement angle: (a) 1(111)/1(200) = 3;(b)I(111)/I(200) = 78; (c) 1(111)/1(200) = 960.

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~iopm Fig. 6. Scanning ~Iectron micrographs ol eroded surfaces of TiN coatings formed by alumina erosion at 30° impingement angle: (a)I(111)/I(20G) 3; (b)I(111)/I(200) = 78; (c) 1(111)/1(200) = 960.

nation of a highly plastically deformed layer owing to repeated impacts. A more uniform surface with microfracture and relatively smaller impact indentations was obtained with a coating with an 1(111)/1(200) value of 960 (Fig. 5(c)). These observations of erosion at normal impact can be explained by either Hertzian stress cracking or work hardening leading to delamination. Plastic deformation of the surface results in work hardening, crack propagation and, ultimately, delamination whereas Hertzian stresses result in the formation of median, radial and lateral cracks in the coating so that material removal is caused by the intersection of cracks. Based on the morphology of the eroded surfaces, a coating with a higher value of 1(111)11(200) is clearly more resistant to fracture. Therefore, higher values of fracture toughness K~would be expected in coatings with a higher value of 1(111)1 1(200). Thus, using either explanation, brittle fracture is the predominant mechanism for alumina erosion in TiN coating at normal impact. In the 30°impact, a ploughing mode of plastic deformation prevails in the eroded surfaces (Figs. 6(a) (c)). A substantial lateral displacement of material appears as a raised rim ahead of and around ploughing scars. The size and penetration depth of ploughing scars decrease with increasing values of 1(111)11(200). Based on the change in coating hardness, the size of ploughing scars should increase with increasing 1(111)11(200) value when above 40. This is contrary to the observations in Figs. 6(b) and (c). Clearly, other factors besides coating hardness have significant effects on the erosion -

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process at 30°impact.In general, the slip planes (most closely packed planes) in the crystal exhibit the highest resistance to abrasion. Thus, the decrease in the size of the ploughing scars (Figs. 6(a) (c)) may be attributed to the increase of the I(111)/I(200) value. Generally, ductile and brittle materials exhibit distinctly different erosion behavior. The maximum erosion of a ductile material such as pure aluminum occurs at a glancing angle of about 20° or greater [54 561, depending on the test parameters, whereas a brittle material such as glass has a maximum at 90°[54]. The effects of impact angles and I(111)/I(200) values of TiN coatings on their erosion behavior are shown in Fig. 7. The curves of typical brittle and ductile behavior obtained respectively from a flame-sprayed tungsten-carbide—cobalt coating and 6061 aluminum are also shown in Fig. 7 for comparison. The maximum erosion rate of 6061 aluminum appears at about 45°,because of the use of penetration depth as a measure for erosion instead of the volume loss. The TiN coating with a I(111)/1(200) value of 3 exhibits a typical brittle behavior. As the I(111)/ 1(200) value increases from 3 to 960, the erosion rate decreases substantially and erosion behavior changes from a type of brittle erosion to a combination of ductile and brittle. It is likely that the increase in the 1(111)/I(200) value -

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ALUMINA EROSION 27 urn PARTICLE SIZE 91 rn/s.c PARTICLE VELOCITY 1.2 cm NOZZLE TO WORKPIECE DISTANCE

80

60

I

~ /~~E/’~’~

WC-Co COATEIG

y./~”~(1ifl/[(2OO)~22O

1 1)/I (20O)~96O

IMPACT ANGLE (DEGREES) Fig. 7. Erosion of TiN coatings as a function of impingement angle and 1(111)/1(200) value.

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is associated with an increase in fracture toughness K~and a decrease in hardness H of the coating. Rickerby et al. [57] have shown that the erosion rate of single crystalline MgO depends on crystallographic orientation when subjected to spherical chrome steel and WC particle impact. Shin [58] has found the basal plane (0001), a close-packed plane, of a synthetic a quartz is more erosion resistant to 760 jim glass beads than are the prism plane (1100) or the pyramidal plane (1120). However, no effect of crystallographic orientation on erosion of a quartz is observed when subjected to 30 jim angular Al203 particles of 112 m s~velocity. However, this result does not generally apply to the erosion behavior of all brittle materials. The erosion resistance of TiN coatings to 27 jim angular A1203 particles is strongly dependent on their crystallographic orientation. As shown in Fig. 4, the erosion rate of TiN coatings is inversely proportional to the value of lg{I(111)/1(200)}. It is suggested that the difference in erosion behavior between single-crystal a quartz and polycrystalline TiN coating may be attributed to the threshold of orientation dependence. This threshold is probably dependent on the velocity, size and shape of the impacting particles, as well as on the hardness and fracture toughness of the target material. Erosive wear tests of 30

jim

angular alumina with a 112 m s’ velocity may be too severe and exceed the orientation dependence threshold for a quartz. Accordingly, more pronounced dependence on 1(111)11(200) would be expected for TiN coatings when exposed to the impact of spherical or rounded particles such as silica dust compared with large, angular alumina particles. Erosion resistance, however, is certainly not dependent on a single-

value property of test materials. In addition to the effects of hardness, fracture toughness and microstructural features such as grain size, porosity and crystallographic orientation clearly play an important role in the erosion process.

4. Conclusions TiN coatings produced with a modified (Union Carbide) arc evaporation process exhibit very much higher (111) preferred orientation, than those produced with other PVD and CVD processes. The ratio of X-ray diffraction intensity from the (111) plane to that from the (200) plane, 1(111)/1(200), was used to rank quantitatively the degree of (111) preferred orientation of the coatings. The microstructure, hardness and erosion be-

havior of the PVD arc evaporation TiN are strongly dependent on the 1(111)/1(200) value. The erosion rates of TiN coatings at 90° and 30°impingement angles are respectively given by the empirical equations W~,= 60.5 and

—

14.9 X lg{I(111)/I(200)}

180

Wi,,

=

8.3

—

1.8 X lg{I(111)/I(200)}

where W~is in micrometers per gram. SEM examinations of eroded surfaces reveal that brittle fracture and ploughing are the primary mechanisms for TiN at 90° and 30° alumina erosion respectively. Based on this investigation, it is clear that the highly (111) oriented TiN coating has a definitive advantage in erosion applications. Acknowledgments We are grateful to R. D. Johnson and J. 0. Dillon for preparation of the coatings, R. E. Newman for doing some of the X-ray diffraction measurements, and N. T. Pham for doing the alumina erosion test. We also thank the Metallographic Laboratory personnel for their contribution. References G. Persson, Met. Prog., 97 (1970) 81. W. Schintimeister, W. Waligram and J. Kanz, Thin Solid Films, 107 (1983) 117. A. Pan and J. E. Greene, Thin Solid Films, 78 (1981) 25. A. Matthews and D. G. Teer, Thin Solid Films, 72 (1980) 541. R. Buhl, H. K. Pulker and E. Moll, Thin Solid Films, 80 (1981) 265. T. Jamal, R. Nimmagadda and R. F. Bunshah, Thin Solid Films, 73 (1980) 245. Toshiro Yamashina, Hiroshi Aida, Osamu Kawamoto and Masaaki Suzuki, Thin Solid Films, 108 (1983) 395. 8 M. K. Hibbs, B.-O. Johansson, J.-E. Sundgren and V. Helmersson, Proc. mt. Conf. 1 2 3 4 5 6 7

Metallurgical Coatings, San Diego, CA, April, 1984. 9 B. E. Jacobson, R. Nimmagadda and R. F. Bunshah, Thin Solid Films, 63 (1979) 333. 10 K. Nakamura, K. Inagawa, K. Tsurvoka and S. Komiya, Thin Solid Films, 40 (1977) 155. 11 William D. Sproul, Thin Solid Films, 107 (1983) 141. 12 E. H. Sirvio, M. Sulonen and H. Sundquist, Thin Solid Films, 96 (1982) 93. 13 A. Mumtaz and W. H. Class, J. Vac. Sci. Technol., 20 (1982) 345. 14 A. K. Sun, R. Nimmagadda and R. F. Bunshah, Thin Solid Films, 72 (1980) 529. 15 A. J. Aronson, D. Chen and W. H. Class, Thin Solid Films, 72 (1980) 535. 16 K. Yabe, M. Suzuki, Y. Igasaki, M. Nagakubo, M. Mohri and T. Yamashina, Proc. 7th ICVM, Tokyo, Japan, 1982, p. 246. 17 S. Schiller, G. Beister and W. Sieber, Thin Solid Films, 111 (1984) 259. 18 Takeo, Oki, Proc. 7th ICVM, Tokyo, Japan, 1982, p. 110. 19 A. J. Perry, Thin Solid Films, 135 (1986) 73. 20 A. J. Perry, J. Vac. Sci. Technol., A4 (6) (1986) 2670; (1986) 2674. 21 M. K. Hibbs, J.-E. Sundgren, B. E. Jacobson and B.-O. Johansson, Thin Solid Films, 107 (1983) 149. 22 J.-E. Sundgren, B.-O. Johansson, H. T. G. Hentzell and S.-E. Karisson, Thin Solid Films, 105 (1983) 345. 23 J. E. Sundgren, A. Rockett, J. E. Greene and U. Helmersson, J. Vac. Sci. Technol., A4 (6) (1986) 2770. 24 J.-E. Sundgren,B.-O. Johansson and S.-E. Karlsson, Thin Solid Films, 105 (1983) 353. 25 T. Yamashina, H. Aida and 0. Kawamoto, Thin Solid Films, 108 (1983) 395.

181 26 G. Lemperiere and J. M. Poitevin, Thin Solid Films, 111 (1984) 339. 27 J.-E. Sundgren, B.-0. Johansson, S.-E. Karisson and H. T. G. Hentzell, Thin Solid Films, 105 (1983) 367. 28 Y. Igasaki and H. Mitsuhashi, Thin Solid Films, 70 (1980) 17. 29 L. Chollet and A. J. Perry, Thin Solid Films, 123 (1985) 223. 30 A. J. Perry and L. Chollet, J. Vac. Sci. Technol., A4 (6) (1986) 2801. 31 D. S. Rickerby, J. Vac. Sci. Technol., A4 (6) (1986) 2809. 32 C. Y. Ting, J. Vac. Sci. Technol., 21 (1) (1982) 14. 33 K. Y. Ahn, M. Wittmer and C. Y. Ting, Thin Solid Films, 107 (1983) 45. 34 Y. Enomoto, K. Yamanaka and Kazuyuki Mizuhara, Proc. 7th ICVM, Tokyo, Japan, 1982, p. 209. 35 A. Erdemir and R. F. Hochman, J. Mater. Energy Sys., 7 (3) (1985) 265. 36 A. Erdemir, W. B. Carter and R. F. Hochman, Mater. Sci. Eng., 69 (1985) 89. 37 Seiji Motojima and Masanori Kohno, Thin Solid Films, 137 (1986) 59. 38 A. Matthews and H. A. Sundquist in Proc. mt. Ion Engineering Congress, ISIAT 83, Kyoto, Institute of Electrical Engineers, Japan, 1983. 39 A. A. Snapper, U.S. Patent 3,625,848, 1971. 40 L. P. Sablev, N. P. Atamansky, V. N. Gorbunov, J. I. Dolotov, V. N. Lutseenko, V. M. Lunev and V. V. Usov, U.S. Patent 3,793,179, 1974. 41 L. P. Sablev, J. I. Dolotov, L. I. Getman, V. N. Gorbunov, E. 0. Goldiner, K. T. Kirshfeld and V. V. Usov, U.S. Patent 3,783,231, 1974. 42 A. A. Snapper, U.S. Patent 3,836,451, 1974. 43 J. A. Sue and H. H. Troue, U.S. Patent Application 781,460, 1985. 44 ASTMG76-83. 45 M. Kobayashi and Y. Doi, Thin Solid Films, 54 (1978) 67. 46 M. S. Kim and J. S. Chun, Thin Solid Films, 107 (1983) 129. 47 ASTM X-Ray File 6-0642. 48 J. M. Molarius, A. S. Korhonen and E. 0. Ristolainen, J. Vac. Sci. Technol., A3 (6) (1985) 2419. 49 I. N. Martev, 0. I. Grigorov, I. G. Petrov and E. Dynowska, Thin Solid Films, 131 (1985) 303. 50 A. Matthews and A. R. Lefkow, Thin Solid Films, 126 (1985) 283. 51 H. Randhawa, J. Vac. Sci. Technol., A4 (6) (1986) 2755. 52 E. Hummer and A. J. Perry, Thin $olid Films, 101 (1983) 243. 53 P. K. Mehrotra, D. T. Quinto and G. J. Wolfe, in Mc D. Robinson, C. H. J. van den Brekel, G. W. Cullen, J. M. Blocher, Jr., and P. Rai-Choudhury (eds.), Proc. 9th mt. Conf. CVD, The Electrochemical Society, Pennington, NJ, 1984, p. 757. 54 I. Finnie, Wear, 3 (1960) 87. 55 W. Tabakoff, R. Kotwal and A. Hamed, Wear, 52 (1979) 161. 56 Y. Shida and H. Fujikawa, Wear, 103 (1985) 281. 57 D. G. Rickerby, B. N. Pramilabai and N. H. MacMillan, J. Mater. Sci., 14 (1979) 1807. 58 Y. W. Shin, Multiparticle erosion of synthetic a quartz single crystals, MS. thesis, University of Kentucky, 1979.