SURFACE COATING
IIT Bombay has devised a method to coat steel that improves the quality of diamond coat on steel components, thus enhancing adhesion and giving the surface more hardness.
In the conventional chemical vapor deposition (CVD) method, the first carbon atoms (of the diamond) diffuse into the steel and form graphite clusters. Then, when further deposition happens, the diamond gets deposited on graphite rather than on steel. This process, therefore, does not result in good hardness of steel.
Now, IIT Bombay’s method takes care of this problem.
First the steel surface is cleaned by washing components with detergent, followed by deionized water. Next the components are washed with an aqueous alkali solution and then deionized water. Lastly to remove oxides on the outer layer of steel electro-cleaning or anodic is done using a sulphuric acid bath. The clean component is further electroplated with a strike layer of nickel 0.05 to 1.2 microns thickness. It is then further electroplated with a nickel- diamond composite layer of 15 to 30 microns thickness. On this processed layer a chromium layer of 3-8 microns thickness is added also by electroplating. The next step is to use chemical vapour deposition coating of diamond as known.
The three pre-layers are thermally stable. The nickel layer enhances the second nickel-diamond coating, chromium helps adhering of diamond very well. These layers have helped to solve the problem of poor adhesion due to formation of graphite cluster on bare steel formed during CVD. Carbon does not diffuse into steel because the three layers of chromium, nickel-diamond and nickel form a barrier.
Hence, adhesion on steel components has been drastically improved. The adhesion was verified using scanning electron microscopy, Raman spectroscopy, and micro-hardness gauging methods showing good adhesion thus greater hardness.
This technology is good for application in industries such as grinding and cutting tools, abrasive wheels, ball bearings and medical and dental instruments.
For further details, get in touch with:
The Dean (Research & Development),
2nd Floor, IRCC – SOM Building,
Indian Institute of Technology Bombay,
Powai, Mumbai 400 076
Phone :91-22-2576 7030/7039
Fax :91-22-2572 3702
email :dean.rnd[at]iitb.ac.in
