Enhancement in the Growth of Textured HFCVD Diamond Coatings on Ti-6Al-4V Substrates by Excimer Laser Processing
- PDF / 2,102,050 Bytes
- 5 Pages / 417.6 x 639 pts Page_size
- 44 Downloads / 141 Views
159 Mat. Res. Soc. Symp. Proc. Vol. 585 © 2000 Materials Research Society
diamond films change with different approaches.The goal of this research is to investigate the characteristics of diamond films deposited on Ti-6A1-4V substrates, pretreated using two approaches: (i) seeding with diamond particles, and (ii) surface modification by laser ablation. A detailed analysis of the structure of films and diamond/titanium interfaces were carried out using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy. EXPERIMENTAL Diamond films were grown on Ti-6A1-4V substrates of 2 mm thickness and 5 mm diameter. For comparative results of depositions, two approaches were utilized for substrate pretreatments: seeding with diamond particles on a mirror-polished surface and modifying surface structure by laser ablation. An ultra-sonic agitation in a solution of methanol was used for removing the residues. Seeding of substrates was done in a diamond particle solution in methanol using the same agitation device for 15 minutes. For laser ablation, a pulsed excimer laser was utilized. The surfaces of the substrates were modified using KrF ( %= 248 nm, T = 20 ns) excimer laser. A repetitive pulsed irradiation was done in a 10-6 Torr vacuum at room 2 temperature. Incident laser energy density was 0.5 J/cm for a 100 pulse period. The substrate was rotated while under irradiation with laser pulses in order to produce a circular damage path on the substrate surface. A hot filament CVD system was used for diamond deposition. The substrate was maintained at 600*C. The tungsten filament operating at 2100'C was aligned parallel to the length of the substrate about 4 mm above it. The substrate temperature was measured by means of a thermocouple in contact with the bottom of the substrate. Diamonds were grown with a methane concentration of 1.5% in 100% hydrogen. The ambient pressure was maintained at 20 Torr during deposition. The deposition time was in the range of 4-6 hours 3500
a]
1332
'
-2500"
S500 966
1140
1314
1488
1662
1836
R== Shift (m") Fig.1 (a) Raman spectrum and (b) SEM image of diamond film deposited on Ti6AI-4V substrate with diamond particle seeding.
160
RESULTS AND DISCUSSION
The Raman spectra of diamond films deposited on Ti-6A1-4V substrates with seeding by diamond particles is shown in Fig.1. The Raman peak at 1332 cm-'confirms the sp3 bonding of the diamond structure. Also, it shows that the film is totally unstressed and the film is poorly adhered to the substrate [9-11,14]. The presence of amorphous carbon is not significant as indicated by a small broad peak at 1524 cm-'. The diamond crystallites shown in Fig.lb appear in the film deposited at low substrate temperature of 600'C for 6 hours. The surface of the film appears as junctions of single crystals that originate from primary growth. The coverage of the surface is about 90%. The size of the crystals is about 2 gim. The crystals have different shapes and spontaneous orientation. We have used the laser irradiation techni
Data Loading...
