Nanodiamonds boost wear resistance of nickel plating
Materials specialist Carbodeon has achieved a threefold improvement in the wear resistance of electroless nickel through the addition of nanodiamonds.
Nanodiamonds are usually synthesised by a detonation process which results in diamond particles with surface functionalisation, enabling them to have a positive charge in solution and to deposit together with the metal ions in the plating process.
Carbodeon, however, has been working to develop modified versions of these nanodiamonds, where the surface functionalisation is specifically controlled. For plating applications, the result is that the particle charge or 'zeta potential' is much higher - around 50% more than traditional nanodiamonds.
This creates an additional separation force between the nanodiamond particles and has enabled the company to develop a liquid dispersion of individual 4 to 6nm particles instead of the traditional clusters measuring from 100nm up to a few microns in size.
The result is that the surface area to volume ratio of the diamonds increases by one to two orders of magnitude. By depositing genuine nanoscale particles into metal plating, Carbodeon aims to make the addition of nanodiamond to metal plating more economic.
Comapny CTO Vesa Myllymaki explained: "Throughout our work at Carbodeon, we have focused on delivering unagglomerated nanodiamond particles into parent materials in order to achieve material improvements with substantially less than 1% diamond content, where previously people have used several percent diamond content in agglomerated form and gained less performance than we have.
"We have already achieved this with nanodiamonds in polymer coatings and thermal compounds, and now we have proved it is also possible in certain types of metal plating."
While the traditional dosage rate for plating with agglomerated nanodiamonds is 10g/litre of electrolyte, the optimum dose using dispersed nanodiamond in electroless nickel has been found to be just 0.05g/litre.
Wear testing results using the Taber Rotary Abrasion method show that the as-plated medium phosphorous electroless nickel has a wear index of 6, compared to 18 of the unmodified plating – a threefold improvement.
"Success with nanodiamonds means achieving more with less, and we have done that," Myllymaki continued. "The cost of the diamond in the process is less than the cost of the nickel, and in terms of the total component or system value, this is a really economic way of upgrading the performance of the plated surface."
