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Influence of nitrogen implantation on the hydrogen absorption by titanium
Nuclear
722
Influence of nitrogen by titanium
implantation
Instruments
and Methods
in Physics
on the hydrogen
Research
B59/60
(1991) 722-725 North-Holland
absorption
Y. Sugizaki, T. Furuya and H. Satoh Materials Research Laboratory, Kobe Steel, Ltd., Wakinohamacho, Chuoku, Kobe 6.51, Japan
The influence of nitrogen implantation on the hydrogen absorption by titanium has been investigated as a function of fluence. Titanium was implanted with nitrogen ions at an energy of 35 keV in the fluence range of 1~10’~ to 8x10” ions/cm2. The implanted specimens were cathodically charged with hydrogen and the absorbed hydrogen was analyzed quantitatively. Hydrogen depth profiles were also determined by using an elastic recoil detection technique. The structural changes of the implanted layer accompanying the range of fluences were examined by a glancing angle X-ray diffraction method. It was found that nitrogen implantation significantly affected the hydrogen absorption by titanium at fluences above 6 x lOI the hydrogen contents were markedly increased and the excess ions/cm2. At fluences between 6~10’~ and 2x10” ions/cm2, hydrogen was preferentially distributed in the implanted layer where the implanted nitrogen distorted the titanium lattice. However, the hydrogen content steeply decreased at fluences above 2 X 10” ions/cm*. The suppression of the hydrogen absorption was caused by the retarding effect of titanium nitride precipitation on the hydrogen migration. It was concluded that the hydrogen absorption of the nitrogen implanted titanium depended on the behavior of the implanted nitrogen in the titanium lattice.
1. Introduction Transition
metals
of hydrogen ments
[l].
cipitating
when Excessive hydrides
are undergo [2].
generally they
are
hydrogen
the
of their
effects
up a large
amount
to some
environ-
absorption
in the matrix
degradation
Recently,
pick exposed
of
lattice
leads and
mechanical
ion
implantation
to pre-
the metals properties on
the
such as titanium, iron, nickel and tantalum, have been investigated in connection with hydrogen degradation of the metals or their alloys and the influence of radiation in the first wall of fusion reactors. According to the results reported by Zamanzadeh et al. [3], the hydrogen permeation in an iron membrane implanted with platinum was reduced through the catalytic effect of platinum on the hydrogen evolution reaction. Ensinger and Wolf [4,5] have directly demonstrated the preventive influence of platinum implantation on the hydrogen embrittlement of tantalum by means of a bending test. They have discussed that this effect, introduced by ion implantation, is attributed not only to catalyzing the desorption reaction of hydrogen, but also to stimulating the passivation of tantalum. A thicker passive oxide layer on tantalum may block the diffusion of hydrogen into the bulk. Furthermore, the interaction between hydrogen and the implanted foreign elements in the metals has been studied [6,7]. Schwenk et al. [6] have investigated the effect of the implanted species (Ti, Fe, Cu. and Cr) on the redistribution of hydrogen in nickel and titanium. The results indicated hydrogen
absorption
0168-583X/91/$03.50
of
transition
metals,
0 1991 - Elsevier Science Publishers
that the ion implantation of these species modified the solubility and mobility of hydrogen in these metals. As mentioned above, a selected number of metal ion species such as noble metals have been found to be effective in reducing the hydrogen absorption of transition metals and their mechanism has been discussed by some investigators. However, no investigation has been carried out so far on the effect of light element ion species such as carbon, nitrogen and oxygen. In this work, we have attempted to examine the possibility of nitrogen implantation for reducing the hydrogen absorption by titanium. In order to obtain a detailed account of the influence of nitrogen implantation, the behavior of the hydrogen absorption was systematically studied as a function of fluences. In addition to the measurement of hydrogen depth profiles, the hydrogen content was chemically analyzed at various fluences. These results are discussed in terms of the characterization of the implanted nitrogen in the titanium matrix lattice.
2. Experimental Commercially pure titanium was used as the substrate for nitrogen implantation. The hydrogen content of the as-delivered titanium was 24 ppm. The mechanically polished surface of the specimen was exposed to a nitrogen ion beam in a vacuum of 3 x 10e5 Pa. The nitrogen implantation was carried out at an energy of
B.V. (North-Holland)
Y. Sugizaki et al. / Influence of N implantation on H absorption by Ti
35 keV with a current density of 20 PA/cm’. The temperature during implantation did not exceed 100°C. The fluence was varied in the range of 1 x 1015 to 8 x 10” ions/cm’. Prior to hydrogen charging, glancing angle X-ray diffraction patterns were measured for each specimen in order to characterize the lattice structure of the implanted layer. The implanted specimens were cathodically charged with hydrogen. An electrolysis cell containing O.lN H,S04 at 60°C was set up, where the sample served as a cathode. Hydrogen was evolved on the modified surface. The charging current density was kept at 1 mA/cm for 24 h. The absorbed hydrogen was analyzed by the following method. The hydrogen content was quantitatively analyzed by using an inert gas fusion fusion thermal conductivity technique. Elastic recoil measurements were also carried out to determine the hydrogen depth profile in the near-surface layer. A 2 MeV He ion beam, which was delivered by a 2 MeV Van de Graaff accelerator at the Government Industrial Research Institute in Osaka, impinged on the modified surface at a glancing angle of 1.5 O. The recoiled hydrogen was detected with a solid state detector mounted at a recoil angle of 25 O. Mylar (6 pm in thickness) was used as an absorber for the scattered He ions.
3. Results and discussion The dependence of the hydrogen absorption on the nitrogen fluence was investigated in the range of 1 X 10” to 8 x 10” ions/cm’. Fig. 1 shows the hydrogen content as a function of nitrogen fluence. The hydrogen content was not affected at fluences below 6 X lOi ions/cm’. This was comparable to the unimplanted specimen. Fig.
1
600
10'4
10'5
10’6
10'7
10'8
l(
FLUENCE (ions/cm2)
Fig. 1. Dependence of the hydrogen content absorbed by titanium on the nitrogen fluence. The hydrogen content of the unimplanted specimen (A) is also indicated.
723 Depth ( A )
I
i
1 1000 1
ol’--“~-~ 200
i’/*‘-.
,c
0
CHANNEL
NUMBER
400 (energy)
Fig. 2. Hydrogen depth profiles of the nitrogen implanted specimens with fluences of (1) 5 x 1016, (b) 2~ 10” and (c) 5 X 10” ions/cm2 after being cathodically charged with hydro gen.
2 shows the hydrogen depth profiles for each specimen with three typical nitrogen fluences: 5 X 1016, 2 X 10” and 5 x 10” ions/cm’. The profiles were determined by using an elastic recoil detection method. The hydrogen depth profiles at fluences below 6 X lOI ions/cm’ (fig. 2a) were very similar to that of the unimplanted specimen in shape and amount. Titanium hydride (TiH,) precipitated uniformly in the implanted layer. In the specimens with fluences between 6 x 1016 and 2 x 10” ions/cm2 an excess amount of hydrogen was absorbed. The hydrogen content was increased to about two times as in much as the unimplanted specimen. The hydrogen profile at a fluence of 2 X 10” ions/cm’ is presented in fig. 2b. In comparison with the un-affected samples at the lower fluences, the intensities of the recoil hydrogen were larger at low channels. This corresponded to the implanted layer. The excess hydrogen was preferentially distributed in the nitrogen implanted layer. This result is in agreement with the hydrogen entrapment by oxygen or nitrogen in refractory metals [7-91. However, the amount of absorbed hydrogen steeply decreased at fluences above 2 X 10” ions/cm’. The hydrogen content was comparable to that of the as-delivered titanium. As a consequence of nitrogen implantation at such fluences, the absorption of hydrogen by titanium was almost inhibited. The surface peak due to the adsorbed hydrocarbons or the small amount of the absorbed hydrogen appeared only in the profile, as can be seen in VII. METALS
,’ TRIBOLOGY
Y. Sugizaki et al. / Influence
124
ofN
fig. 2c. It should be noted that there was no intensity of the recoiled hydrogen in the nitrogen implanted layer. The distribution of the hydrogen was blocked in the implanted layer. The variation of the temperature (room temperature, 150°C, 230°C and 340*(Z) of the specimen during implantation greatly influenced the hydrogen absorption. Table 1 presents the hydrogen content for each temperature at a fluence of 3 X 10” ions/cm*. The hydrogen content was decreased with increasing temperature. The specimen implanted at 34O’C had the same hydrogen content and a similar hydrogen profile as the as-delivered titanium. In a previous work [lo], the electr~he~cal properties for hydrogen evolution on the nitrogen implanted surface were studied by measuring the cathodic polarization curves in the charging solution. The curve obtained for each nitrogen implanted specimen was found to be almost the same as for the unimplanted specimen. Wence, it was concluded that the nitrogen implantation did not significantly modify the reactions of hydrogen evolution. A glancing angle X-ray diffraction pattern was measured for each implanted specimen, in order to explain the dependence of the hydrogen absorption on the nitrogen fluence. A comparison of the diffraction patterns at typical fluences is demonstrated in fig. 3. The incident angle of X-rays was lo, which approximately corresponded to 0.3 urn in the surveyed depth for Cu Ku. No change in the diffraction pattern was found at the lower fluences. The pattern was similar to that of the unimplanted specimen. In the pattern of the specimen with the middle fluence, the diffraction lines were broadened. This was especially true for the lines related to the c direction (index I), which were larger than the other lines and were broadened at a lower scattering angle (28). This suggested that the implanted nitrogen occupied the interstitial sites and distorted the titanium matrix lattice in the c direction. The hydrogen in refractory metals is sensitive to the distorted field of the matrix lattice, which produced the nitrogen-hydrogen complexes. and hence caused the hydrogen gettering effect, On the other hand, titanium nitride precipitated in the near-surface layer at the higher fluence, as can be seen in fig. 3c. The diffraction lines due to titanium
Table 1 Effect of the temperature on the hydrogen content of the specimen with a nitrogen fluence of 3 x 10” ions/cm* Temperature [OC]
Hydrogen content [ppm]
Room temperature 150 230 340
195 170 64 36
implantation on H absorption by Ti I
0,
.,
(a)
Y-4
--1---w (5 X 10’6ions/cm2]
o,.,
(2X 1017ions/cm2)
SCATTERING ANGLE, 20
( deg. )
Fig. 3. Diffraction patterns of the nitrogen implanted specimen, obtained by using a glancing angle diffraction method, fluences of (a) 5 X lOI (b) 2 x 10” and (c) 5 x IO” ions/cm* before being ~thodically charged with hydrogen.
nitride were superimposed on those of a phase titanium. It was noted that broadening of the lines did not occur. Titanium nitriding in the implanted layer with higher fluences was comparable with the suppression of the hydrogen absorption. The precipitation of titanium nitride blocked the distribution of hydrogen and prevented the hydrogen migration. As mentioned above, the hydrogen content decreased with an increase in the temperature during implantation. It could be a consequence of the promotion of nitride forming at the higher temperatures. The growth of diffraction lines due to nitride formation was observed with increasing temperature.
4. Conclusion It has been shown in the present work that nitrogen implantation with fluences above 6 X lOI ions/cm2 significantly affects the hydrogen absorption by titanium. The excess hydrogen was absorbed in the implanted layer at fluences between 6 X lOI and 2 x 101’ ions/cm’. Nitrogen ~pl~tation with such fluences
Y. Sugizaki
et al. / Influence of N implantation
produced the stress fields in the implanted layer, which resulted in the hydrogen accumulation. On the other hand, the hydrogen absorption was suppressed at higher fluences where titanium nitride was precipitated in considerable amounts in the Implanted layer. The increase of temperature during implantation was effective in preventing the hydrogen absorption. It could be explained by the enhancement of the concentration titanium nitride with the temperature. The blocking effect of nitride caused the retardation of the inward diffusion of hydrogen and, consequently, the suppression of the motion of hydrogen into titanium. The presented results demonstrate that it is possible to suppress the hydrogen absorption by titanium in acids by nitrogen implantation with higher fluences.
Acknowledgements
The authors would like to thank Dr. Y. Horino and Dr. M. Satou of the Government Industrial Research Institute for perfo~ng the elastic recoil detection measurements. This work was performed under the Research and Development Program on Advanced Material Processing and Machining System, conducted
725
on H absorption by Ti
under a program set up by the New Energy and Industrial Technology Development Organization.
References
VI E.g.: J.B. Cotton, The Science. Technology
and Application of Titanium (Pergamon, 1977) p. 155. VI For example, M.R. Louthan, Jr.. Trans. AIME 227 (1963) 1166. H. Allam, H.W. Pickering and G.K. [31 M. Zamanzadeh, Huber, J. Elcctrochem. Sot. 127 (1980) 1688. (41 W. Ensinger and G.K. Wolf, Mater. Sci. Eng. 90 (1987) 237. 151 W. Ensinger and G.K. Wolf, Nucl. Instr. and Meth. B39 (1989) 552. K. Behge, S. Blumner, Th. (61 H. Schwenk, H. Baumann, Lenz, R. Mohr and F. Rauch, Proc. 3rd Int. Congr. on Hydrogen and Materials, ed. A. Pierre, Paris, 1982, p. 485. 171 C.C. Baker and H.K. Birnbaum, Acta Metall. 21 (1973) 865. 181 K. Rosan and H. Wipf, Phys. Status Solidi A38 (1976) 611. f91 T.H. Metzger, U. Schubert and J. Peisl. J. Phys. F15 (1985) 779. PO1 Y. Sugizaki, T. Furuya and H. Satoh, to be submitted.
VII. METALS
/ TRIBOLOGY
722
Influence of nitrogen by titanium
implantation
Instruments
and Methods
in Physics
on the hydrogen
Research
B59/60
(1991) 722-725 North-Holland
absorption
Y. Sugizaki, T. Furuya and H. Satoh Materials Research Laboratory, Kobe Steel, Ltd., Wakinohamacho, Chuoku, Kobe 6.51, Japan
The influence of nitrogen implantation on the hydrogen absorption by titanium has been investigated as a function of fluence. Titanium was implanted with nitrogen ions at an energy of 35 keV in the fluence range of 1~10’~ to 8x10” ions/cm2. The implanted specimens were cathodically charged with hydrogen and the absorbed hydrogen was analyzed quantitatively. Hydrogen depth profiles were also determined by using an elastic recoil detection technique. The structural changes of the implanted layer accompanying the range of fluences were examined by a glancing angle X-ray diffraction method. It was found that nitrogen implantation significantly affected the hydrogen absorption by titanium at fluences above 6 x lOI the hydrogen contents were markedly increased and the excess ions/cm2. At fluences between 6~10’~ and 2x10” ions/cm2, hydrogen was preferentially distributed in the implanted layer where the implanted nitrogen distorted the titanium lattice. However, the hydrogen content steeply decreased at fluences above 2 X 10” ions/cm*. The suppression of the hydrogen absorption was caused by the retarding effect of titanium nitride precipitation on the hydrogen migration. It was concluded that the hydrogen absorption of the nitrogen implanted titanium depended on the behavior of the implanted nitrogen in the titanium lattice.
1. Introduction Transition
metals
of hydrogen ments
[l].
cipitating
when Excessive hydrides
are undergo [2].
generally they
are
hydrogen
the
of their
effects
up a large
amount
to some
environ-
absorption
in the matrix
degradation
Recently,
pick exposed
of
lattice
leads and
mechanical
ion
implantation
to pre-
the metals properties on
the
such as titanium, iron, nickel and tantalum, have been investigated in connection with hydrogen degradation of the metals or their alloys and the influence of radiation in the first wall of fusion reactors. According to the results reported by Zamanzadeh et al. [3], the hydrogen permeation in an iron membrane implanted with platinum was reduced through the catalytic effect of platinum on the hydrogen evolution reaction. Ensinger and Wolf [4,5] have directly demonstrated the preventive influence of platinum implantation on the hydrogen embrittlement of tantalum by means of a bending test. They have discussed that this effect, introduced by ion implantation, is attributed not only to catalyzing the desorption reaction of hydrogen, but also to stimulating the passivation of tantalum. A thicker passive oxide layer on tantalum may block the diffusion of hydrogen into the bulk. Furthermore, the interaction between hydrogen and the implanted foreign elements in the metals has been studied [6,7]. Schwenk et al. [6] have investigated the effect of the implanted species (Ti, Fe, Cu. and Cr) on the redistribution of hydrogen in nickel and titanium. The results indicated hydrogen
absorption
0168-583X/91/$03.50
of
transition
metals,
0 1991 - Elsevier Science Publishers
that the ion implantation of these species modified the solubility and mobility of hydrogen in these metals. As mentioned above, a selected number of metal ion species such as noble metals have been found to be effective in reducing the hydrogen absorption of transition metals and their mechanism has been discussed by some investigators. However, no investigation has been carried out so far on the effect of light element ion species such as carbon, nitrogen and oxygen. In this work, we have attempted to examine the possibility of nitrogen implantation for reducing the hydrogen absorption by titanium. In order to obtain a detailed account of the influence of nitrogen implantation, the behavior of the hydrogen absorption was systematically studied as a function of fluences. In addition to the measurement of hydrogen depth profiles, the hydrogen content was chemically analyzed at various fluences. These results are discussed in terms of the characterization of the implanted nitrogen in the titanium matrix lattice.
2. Experimental Commercially pure titanium was used as the substrate for nitrogen implantation. The hydrogen content of the as-delivered titanium was 24 ppm. The mechanically polished surface of the specimen was exposed to a nitrogen ion beam in a vacuum of 3 x 10e5 Pa. The nitrogen implantation was carried out at an energy of
B.V. (North-Holland)
Y. Sugizaki et al. / Influence of N implantation on H absorption by Ti
35 keV with a current density of 20 PA/cm’. The temperature during implantation did not exceed 100°C. The fluence was varied in the range of 1 x 1015 to 8 x 10” ions/cm’. Prior to hydrogen charging, glancing angle X-ray diffraction patterns were measured for each specimen in order to characterize the lattice structure of the implanted layer. The implanted specimens were cathodically charged with hydrogen. An electrolysis cell containing O.lN H,S04 at 60°C was set up, where the sample served as a cathode. Hydrogen was evolved on the modified surface. The charging current density was kept at 1 mA/cm for 24 h. The absorbed hydrogen was analyzed by the following method. The hydrogen content was quantitatively analyzed by using an inert gas fusion fusion thermal conductivity technique. Elastic recoil measurements were also carried out to determine the hydrogen depth profile in the near-surface layer. A 2 MeV He ion beam, which was delivered by a 2 MeV Van de Graaff accelerator at the Government Industrial Research Institute in Osaka, impinged on the modified surface at a glancing angle of 1.5 O. The recoiled hydrogen was detected with a solid state detector mounted at a recoil angle of 25 O. Mylar (6 pm in thickness) was used as an absorber for the scattered He ions.
3. Results and discussion The dependence of the hydrogen absorption on the nitrogen fluence was investigated in the range of 1 X 10” to 8 x 10” ions/cm’. Fig. 1 shows the hydrogen content as a function of nitrogen fluence. The hydrogen content was not affected at fluences below 6 X lOi ions/cm’. This was comparable to the unimplanted specimen. Fig.
1
600
10'4
10'5
10’6
10'7
10'8
l(
FLUENCE (ions/cm2)
Fig. 1. Dependence of the hydrogen content absorbed by titanium on the nitrogen fluence. The hydrogen content of the unimplanted specimen (A) is also indicated.
723 Depth ( A )
I
i
1 1000 1
ol’--“~-~ 200
i’/*‘-.
,c
0
CHANNEL
NUMBER
400 (energy)
Fig. 2. Hydrogen depth profiles of the nitrogen implanted specimens with fluences of (1) 5 x 1016, (b) 2~ 10” and (c) 5 X 10” ions/cm2 after being cathodically charged with hydro gen.
2 shows the hydrogen depth profiles for each specimen with three typical nitrogen fluences: 5 X 1016, 2 X 10” and 5 x 10” ions/cm’. The profiles were determined by using an elastic recoil detection method. The hydrogen depth profiles at fluences below 6 X lOI ions/cm’ (fig. 2a) were very similar to that of the unimplanted specimen in shape and amount. Titanium hydride (TiH,) precipitated uniformly in the implanted layer. In the specimens with fluences between 6 x 1016 and 2 x 10” ions/cm2 an excess amount of hydrogen was absorbed. The hydrogen content was increased to about two times as in much as the unimplanted specimen. The hydrogen profile at a fluence of 2 X 10” ions/cm’ is presented in fig. 2b. In comparison with the un-affected samples at the lower fluences, the intensities of the recoil hydrogen were larger at low channels. This corresponded to the implanted layer. The excess hydrogen was preferentially distributed in the nitrogen implanted layer. This result is in agreement with the hydrogen entrapment by oxygen or nitrogen in refractory metals [7-91. However, the amount of absorbed hydrogen steeply decreased at fluences above 2 X 10” ions/cm’. The hydrogen content was comparable to that of the as-delivered titanium. As a consequence of nitrogen implantation at such fluences, the absorption of hydrogen by titanium was almost inhibited. The surface peak due to the adsorbed hydrocarbons or the small amount of the absorbed hydrogen appeared only in the profile, as can be seen in VII. METALS
,’ TRIBOLOGY
Y. Sugizaki et al. / Influence
124
ofN
fig. 2c. It should be noted that there was no intensity of the recoiled hydrogen in the nitrogen implanted layer. The distribution of the hydrogen was blocked in the implanted layer. The variation of the temperature (room temperature, 150°C, 230°C and 340*(Z) of the specimen during implantation greatly influenced the hydrogen absorption. Table 1 presents the hydrogen content for each temperature at a fluence of 3 X 10” ions/cm*. The hydrogen content was decreased with increasing temperature. The specimen implanted at 34O’C had the same hydrogen content and a similar hydrogen profile as the as-delivered titanium. In a previous work [lo], the electr~he~cal properties for hydrogen evolution on the nitrogen implanted surface were studied by measuring the cathodic polarization curves in the charging solution. The curve obtained for each nitrogen implanted specimen was found to be almost the same as for the unimplanted specimen. Wence, it was concluded that the nitrogen implantation did not significantly modify the reactions of hydrogen evolution. A glancing angle X-ray diffraction pattern was measured for each implanted specimen, in order to explain the dependence of the hydrogen absorption on the nitrogen fluence. A comparison of the diffraction patterns at typical fluences is demonstrated in fig. 3. The incident angle of X-rays was lo, which approximately corresponded to 0.3 urn in the surveyed depth for Cu Ku. No change in the diffraction pattern was found at the lower fluences. The pattern was similar to that of the unimplanted specimen. In the pattern of the specimen with the middle fluence, the diffraction lines were broadened. This was especially true for the lines related to the c direction (index I), which were larger than the other lines and were broadened at a lower scattering angle (28). This suggested that the implanted nitrogen occupied the interstitial sites and distorted the titanium matrix lattice in the c direction. The hydrogen in refractory metals is sensitive to the distorted field of the matrix lattice, which produced the nitrogen-hydrogen complexes. and hence caused the hydrogen gettering effect, On the other hand, titanium nitride precipitated in the near-surface layer at the higher fluence, as can be seen in fig. 3c. The diffraction lines due to titanium
Table 1 Effect of the temperature on the hydrogen content of the specimen with a nitrogen fluence of 3 x 10” ions/cm* Temperature [OC]
Hydrogen content [ppm]
Room temperature 150 230 340
195 170 64 36
implantation on H absorption by Ti I
0,
.,
(a)
Y-4
--1---w (5 X 10’6ions/cm2]
o,.,
(2X 1017ions/cm2)
SCATTERING ANGLE, 20
( deg. )
Fig. 3. Diffraction patterns of the nitrogen implanted specimen, obtained by using a glancing angle diffraction method, fluences of (a) 5 X lOI (b) 2 x 10” and (c) 5 x IO” ions/cm* before being ~thodically charged with hydrogen.
nitride were superimposed on those of a phase titanium. It was noted that broadening of the lines did not occur. Titanium nitriding in the implanted layer with higher fluences was comparable with the suppression of the hydrogen absorption. The precipitation of titanium nitride blocked the distribution of hydrogen and prevented the hydrogen migration. As mentioned above, the hydrogen content decreased with an increase in the temperature during implantation. It could be a consequence of the promotion of nitride forming at the higher temperatures. The growth of diffraction lines due to nitride formation was observed with increasing temperature.
4. Conclusion It has been shown in the present work that nitrogen implantation with fluences above 6 X lOI ions/cm2 significantly affects the hydrogen absorption by titanium. The excess hydrogen was absorbed in the implanted layer at fluences between 6 X lOI and 2 x 101’ ions/cm’. Nitrogen ~pl~tation with such fluences
Y. Sugizaki
et al. / Influence of N implantation
produced the stress fields in the implanted layer, which resulted in the hydrogen accumulation. On the other hand, the hydrogen absorption was suppressed at higher fluences where titanium nitride was precipitated in considerable amounts in the Implanted layer. The increase of temperature during implantation was effective in preventing the hydrogen absorption. It could be explained by the enhancement of the concentration titanium nitride with the temperature. The blocking effect of nitride caused the retardation of the inward diffusion of hydrogen and, consequently, the suppression of the motion of hydrogen into titanium. The presented results demonstrate that it is possible to suppress the hydrogen absorption by titanium in acids by nitrogen implantation with higher fluences.
Acknowledgements
The authors would like to thank Dr. Y. Horino and Dr. M. Satou of the Government Industrial Research Institute for perfo~ng the elastic recoil detection measurements. This work was performed under the Research and Development Program on Advanced Material Processing and Machining System, conducted
725
on H absorption by Ti
under a program set up by the New Energy and Industrial Technology Development Organization.
References
VI E.g.: J.B. Cotton, The Science. Technology
and Application of Titanium (Pergamon, 1977) p. 155. VI For example, M.R. Louthan, Jr.. Trans. AIME 227 (1963) 1166. H. Allam, H.W. Pickering and G.K. [31 M. Zamanzadeh, Huber, J. Elcctrochem. Sot. 127 (1980) 1688. (41 W. Ensinger and G.K. Wolf, Mater. Sci. Eng. 90 (1987) 237. 151 W. Ensinger and G.K. Wolf, Nucl. Instr. and Meth. B39 (1989) 552. K. Behge, S. Blumner, Th. (61 H. Schwenk, H. Baumann, Lenz, R. Mohr and F. Rauch, Proc. 3rd Int. Congr. on Hydrogen and Materials, ed. A. Pierre, Paris, 1982, p. 485. 171 C.C. Baker and H.K. Birnbaum, Acta Metall. 21 (1973) 865. 181 K. Rosan and H. Wipf, Phys. Status Solidi A38 (1976) 611. f91 T.H. Metzger, U. Schubert and J. Peisl. J. Phys. F15 (1985) 779. PO1 Y. Sugizaki, T. Furuya and H. Satoh, to be submitted.
VII. METALS
/ TRIBOLOGY