How Much Does DLC (Diamond Like Carbon) Coating Cost on Titanium Parts - Compare USA PVD Suppliers
I was first introduced to DLC Coating (Diamond-Like Carbon) by customers of our MARKSMITH Ti Bolt Action Marker when we were investigating different black coatings that could be applied to titanium. The coating needed to be the most durable available, so that it would not wear off. DLC claims to be one of the hardest, most wear-resistant coating that has a very low coefficient of friction.
DLC coating is applied via the PVD process, so most services that offer PVD will also offer DLC. Often they have several different versions of DLC coating depending on your application.
Here's a research paper about the Wear and corrosion properties of diamond like carbon (DLC) coating on stainless steel, CoCrMo and Ti6Al4V substrates
The final appearance of the part after DLC coating will depend on the surface finish prior to coating. The coating is extremely thin, and therefore the part surface finish will show through. I've received some conflicting information from different PVD vendors about the minimum surface finish required for the DLC coating to bond properly to the surface.
UPT-USA said that they could offer several different surface finishes, from a fine bead blast to polished, prior to applying the DLC coating. They knew that the application was primarily cosmetic and that I was interested in a finish that was more matte than shiny.
These are the surface finishes UPT offered:
Matte Finish - bead blast
Satin Finish - vapor honing
Shiny - Polished
UPT-USA's price quote for 100 small cylindrical pieces was the same as Calico Coatings but did not include pre-finishing the surface to a low roughness like Calico wanted to do. UPT also said that they could only fit 50 or so pieces in the chamber per batch, so they must have a smaller chamber than Calico Coatings who claimed that they could fit much more than 100 pieces per batch.
Calico Coatings said that for proper bonding of the coating, the surface required a finish that had a roughness of less than 5 microinch RA, which according to the chart below is pretty close to a mirror finish. The parts I was quoting with them was the internal piston of the MARKSMITH, and the reason for coating was to create a harder surface with a lower coefficient of friction. Those parts were originally sanded to about 400 grit, which according to the chart is 9 microinch RA, and Calico Coatings did not think that was a good enough surface finish. It's possible that Calico is being more cautious about the surface finish than other PVD service providers so that there are no concerns about the final coating quality or premature wear.
The price quoted by Calico Coatings was the same as UPT-USA, but included the surface finishing to decrease the surface roughness below 5 microinch RA.
Calico said that they could fit many more in the chamber than my 100 piece qty, and therefore price would go down with more.
Richter Precision did not suggest an ideal surface roughness. I told them that the surface finish was about 400 grit, and they seemed fine with that. Richter Precision's quote was also about 40% less expensive than the others.