DEPTH PROFILING AND MICROANALYSIS OF HYDROGEN IN TITANIUM

(1)

HAL Id: jpa-00223840

https://hal.archives-ouvertes.fr/jpa-00223840

Submitted on 1 Jan 1984

HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

DEPTH PROFILING AND MICROANALYSIS OF HYDROGEN IN TITANIUM

D. Beaman, H. Klassen, L. Solosky, D. File

To cite this version:

D. Beaman, H. Klassen, L. Solosky, D. File. DEPTH PROFILING AND MICROANALYSIS OF HYDROGEN IN TITANIUM. Journal de Physique Colloques, 1984, 45 (C2), pp.C2-721-C2-727.

�10.1051/jphyscol:19842167�. �jpa-00223840�

(2)

JOURNAL DE PHYSIQUE

Colloque C2, supplément au n°2, Tome 45, février 1984 page C2-721

DEPTH PROFILING AND MICROANALYSIS OF HYDROGEN IN TITANIUM

D.R. Beaman, H.E. Klassen, L.F. Solosky and D.M. File*

Dow Chemical Company, 574 Bldg., Midland, MX 48640, U.S.A.

*U.S. Naval Weapons Support Center, Crane, IN 47522, U.S.A.

Résumé - L'hydrogène a des effets importants sur les propriétés des mé- taux. En particulier la teneur en hydrogène et sa distribution dans le titane doivent être connues pour de nombreuses applications. Dans cette con- tribution on décrit diverses méthodes d'analyse chimique, de mesure de pro- fil, de microanalyse et d'analyse de surface, méthodes utilisées pour ca- ractériser la distribution et l'état de l'hydrogène dans le titane.

Abstract - Hydrogen has dramatic effects on the properties of metals and the quantity and distribution of hydrogen in titanium is an important con- sideration in many applications. This report describes methods of chemical analysis, depth profiling, microanalysis and surface analysis useful in studying the distribution and state of hydrogen in titanium.

RESULTS AND DISCUSSION Bulk Chemical Analyses

If sufficient hydrogen exposure has occurred, a brittle bulk hydride layer will form (Figure 1 ) . It can be delaminated from the substrate and bulk analyzed for Ti by neutron activation analyses and for H by combustion analysis (950°C in purified oxygen). The H/Ti weight ratio can be used to identify the hydride based on stoichiometry. The H/Ti ratio measured herein of 0.0405 was in good accord with the results of x-ray diffraction which identified the hydride as TiH (H/Ti = 0.040).

Depth Profiling

Chemical etching of polished cross-sections readily, but not specifically, reveals a region of bulk hydride overlaying a two phase region consisting of acicular titanium hydride and a Ti (Figure 1 ) . At low hydrogen exposures the acicular hydride appearance is similar to that of nitride? and mechanical twins. The thickness of the bulk hydride can be estimated by measuring the impact strength of the hydrided Ti because the Charpy impact strength shows an approximate loss of 0.9 ft. lbs. per Mn> of bulk hydride thickness up to about 200 (jm.

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19842167

(3)

C2-722 JOURNAL

DE

PHYSIQUE

Figure 1

Polished and etched cross-sections o f titanium after different hydrogen exposures. A shows about 350 pm o f bulk hydride while B shows nil bulk hydride. The marker represents 250 pm.

Krolls etchant: 2 ml HF, 10 ml H N 0 3 , 30 ml lactic acid; swab for 20 seconds.

(4)

Secondary ion mass spectrometry (SIYS) performed in an ion probe is ex- ceptionally useful for studying H in metals (1). Figure 2 is a SIMS profile across the Ti section shown in Figure 1A. The H+ counts clearly delineate the regions of bulk hydride, hydride

+

a Ti and finally a region of dissolved hydrogen which extends for hundreds of pm. The 5 1 ~ i ~ + profile was similar. The depth of hydrogen penetration was in accord with that predicted by bulk diffusion. The detection limit in this analysis was 1 at.% H. Figure 3 is a H

+

image of the interfacial region between bulk hydride and hydride + a Ti.

l i t cwne an Atom

% Hydrogen

bulk hydrlde

-

Tun2 + a T I

no vnrtble hydrlde preclpttatlon

67 Conditions: IMS 3M)

30 pm analysis diameter 5.5 kV 0;

Depth in rrm

I Figure 2

SIMS Depth Profile:

d

counts versus depth in

T i

Microhardness mbasurements provide a simple but non-specific means of profiling. Figure 4 shows a microhardness gradient which mimics the SIMS profile in Figure 2. The SIMS and microhardness gradient measurements are for samples with different hydrogen exposures accounting for the dif- ferences in bulk hydride thicknesses.

(5)

JOURNAL DE PHYSIQUE

Titanium hyd~

and oc T i Bulk

Hydride

Figure 3

ride

H

' image obtained on IMS 300 showing the interfacial region between the bulk hydride and the two phase region of hydride

+

^aTi.

The marker represents 100 pm.

K n q hardnen number - KHN

I

Conditions: Knoop indenter 1W g load 20x objective

-

^R,20

. .

Ti' wbrtrate

Figure 4

100-

0

Microhardness Profile

bulk hydride

, . m h y d r i d e aeicular TiHl +or Ti precipitation

I I

1W 2W 300 4W

Depth in prn

(6)

Depth profiling by Auger electron spectroscopy (AES) using Ar sputtering

+

was unsatisfactory because it promoted hydride decomposition.

Microanalysis

S c a ~ i n g Auger Microanalysis (SAM) with little or no ion sputtering is usoful because the peak-to-peak amplitude of the LMV (418 eV) and MW (27 eV) transitions are markedly reduced in the hydride (Figure 5). The ratios of hydride titanium signal to metallic titanium signal at 418 and 27 eV were 0.81 and 0.67 respectively. It is required that C, N and 0 be absent from the survey spectra if this significant decrease in Ti signal is to be specifically associated with hydride. The reduced Ti emission can be used to map the hydride distribution (2, 3) as shown in the inset of Figure 5.

The hydride spectrum (lower scan in Figure 5) shows a small spectral feature at 410 eV which is not evident in the Ti metal spectrum (upper scan).

Ptgure 5

Auger Emission Spectrum for TI (upper) and TI Hydr~de (lower) TI (418 ev) map at TI/TI Hydr~de interface (lower left).

Cond~t~ons 5kV

T ~ t a n ~ u m Hydrlde

0 Electron Energy, eV

(7)

C2-726 JOURNAL DE PHYSIQUE

The electron probe can be used to quantitatively measure the Ti concentra- tion in spatially localized hydrides with a relative error of

+

^1%. ^Using

a 1071 quartz crystal spectrometer and primary electron beam energy of 15 KV, a reproducible 0.4

+

0.1 eV shift to lower energy was observed in the TiK$ x-ray line energy when comparing Ti hydride and Ti metal. This shift

1

is similar to that reported for titanium oxides, nitride and carbide (4).

Thus, the electron probe can provide relatively unambiguous results by combining its quantitative microanalysis and high spectra1 resolution capabilities.

Surface Analysis

SIMS, as mentioned above, probably offers the most satisfactory means of detecting thin regions of hydride at the surface of Ti. The alteration in the Ti LMV Auger spectrum is small and may not be specific (Figure 5) to hydride. No measurable shift in the Ti (2p 3/2 at 454 eV) binding energy could be measured by x-ray photoelectron spectroscopy. This is not in accord with the measurable shift reported by Nefedov et. al. (5).

CONCLUSION

Utilizing a number of complementary techniques it is possible to unam- biguosly measure the penetration and distribution of hydrogen and hydride in titanium subjected to hydrogen exposure. This includes dissolved hydrogen as well as titanium hydride. Every technique of possible use has not been included and there are two that should be of significant utility, namely, laser microprobe mass analysis (LiVPlA) and analytical transmission electron microscopy-electron energy loss spectroscopy <AT!?:- EELS).

INSTRUMENTATION

A Perkin Elmer 240C elemental analyzer was used to perform automated C, H and N analyses. Neutron activation analyses were carried out using the 100 kilowatt Dow TRIGA reactor; counting was with a Ge(Li) detector. A Philips vertical diffractometer with a long fine focus Cu x-ray source, inter- faced to a LSI 11 computer for data collection and reduction was used in the x-ray diffraction work. The SIMS profiles and H

+

maps were obtained with a Cameca IMS 300 ion probe. Microhardness measurements were made on a Service Diamond microhardness tester using a Knoop indenter and 100 g load.

The Auger experiments were carried out in a Physical Electronics model 545 Scanning Auger Microprobe (SAM) at 5 KV primary beam energy. The electron probe was a Cameca MS46 operated at 15 KV. A Physical Electronics model 550 ESCA was used.to do the x-ray photoelectron spectroscopy.

(8)

ACKNOWLEDGEMENTS

The authors gratefully acknowledge the measurements made by, and useful discussions with the following persons from The Dow Chemical Company: D.

Hawn (XPS); S. Konopnicki (bulk hydrogen); K. Kelly (bulk titanium by neutron activation analysis); T. Fawcett (x-ray diffraction); and D. Donner

(Charpy impact).

REFERENCES

1. Birnbaum, H. K., Fukushima, H and Baker, J. in Adv. Tech. Charact.

Hydrogen Met., Edited by Fiore, N. F. and Berkowitz, B. J., J. Metall.

Soc. AIME, Warrendale, PA, 1982, p. 149.

2. Malinowski, M. E., J. Vac. Sci. Tech. l5, 1978, p. 39.

3. Stulen, R. H., Appl. Surf. Sci.

5 ,

^1980,^{p. 212.}

4. Chirkov, V. I., Blokhen, S. M. amd Vainshtein. E. E., Soviet Physics- Solid State,

?,

1967, p. 873.

5. Nefedov, V. I., Salyn, Ya. V., Baranovskii, I. B., Nikolskii, Soviet Physics-Solid State,

22,

1977, p. 1715.