PSI - Issue 20

Sharin P.P. et al. / Procedia Structural Integrity 20 (2019) 236–241

239

Sharin P.P. et al. / Structural Integrity Procedia 00 (2019) 000–000

4

a

b

c

d

g

h

e

f

Fig. 2. SEM-images of (a-d) diamond; a tablet of (e) chromium; (f) cobalt; (g) iron; (h) titanium surfaces after contact pairs separation.

Table 2. X-ray diffraction analysis of diamond-metal contact pairs surfaces after separation. Phase Separated surface Diamond Cr-tablet Diamond Co-tablet Diamond

Fe-tablet

Diamond

Ti-tablet

Diamond Graphite

+ +

-

+ +

- -

+ +

+ +

+

- -

+

-

Me

Cr

С r

-

Co

Fe

Fe

Ti

Ti

Me x C y Me x O y

С r 3 C 2 Cr 2 O 3 traces

- -

Co 3 C

Co 2 C CoO

Fe 3 C Fe 2 O 3

Fe 3 C Fe 2 O 3

TiC

TiC

-

-

-

In the diamond-chromium tablet contact pair, separation occurs along the coating-chromium tablet boundary, which indicates a strong adhesion of the diamond to the coating due to the formation of a chemical bond between the diamond and the metal-carbide coating. Graphite is formed as a local areas, without forming a continuous layer in contact pairs diamond-iron and diamond-chromium. The presence of a solid graphite layer in the diamond-cobalt contact zone reduces the contact strength by almost an order of magnitude compared to a diamond-chromium contact pair. In the diamond-titanium tablet contact pair, it was not possible to record the force at separation: the strength of the connection was so low that the separation of the contact pair occurred from the touch of tweezers.

Table 3. Diamond-metal contact strength. Contact pair (MPa) Diamond-Fe 24.12 Diamond-Cr 6.76 Diamond-Co 0.68 Diamond-Ti -