Diamond Like Carbon (DLC) on bucket type cam followers 6

[red4re]

I am rebuilding a double overhead V-6 engine and have noticed wear on the bucket cam followers and would like to know if anyone has had a good result with DLC coatings applied to the cams and or followers?

 

[Frederick]

You fellows are right about a thin coating needing to be supported by the metal under it. On parts such as cam followers you can get fatigue failures of the metal under the coating. That is why we recommend that the parts be cryo treated after the coating. This increases the life of the metal under the coating by increasing its fatigue life.

The use of coatings has to be looked at as part of the entire metallurgical and tribilogical concept of the part.

 

[turbocohen]

A bit off topic.. a decade ago I was developing natural gas fuel injectors. Being a gas we had to design for anything from bone dry to wet to oil to goop. One of the guide wear mechanisms, fretting corrosion, was approached in one series of tests using a diamonex coating and it initially worked well when the parts were run dry but the problem was that without deburring the dlc seemed to prevent normal wearin and small burrs acted like a stylus and scratched Rc60 valve needles.
We electropolished some guides and sent them out to diamonex

http://www.diamonex.com/

and those parts went into a batch of injectors that showed the most wear we had ever seen. Back to the drawing board.. the parts that held up best were crude punched "nitronic 60" without any deburring or polishing. Later on we tried diamonex for armature iumpact faces and had mixed results. The dlc parts would accelerate the wear on chrome hardface parts but we found much improved wear when dlc instead of chrome was applied to an armature riding in a soft stainless guide. The relatively hard subsurface did not lose the dlc coating after a billion or so cycles and stopped corrosion reasonably well to our surprise.

 

[markgoldberg]

From what I have heard, Mazda has added DLC as discussed to the manual transmission of their MX-5 Miata and some other models for 2010. The manual transmissions in the 09 were also changed with regard to use of larger shaft diameters and hardening.