Hardfacing on Engine Valves

VMS-1016, AN IRON-BASE MATERIAL WITH A NOMINAL COMPOSITION OF 1.8C, 0.8SI, 10NI, 25CR, 5.5MO, BAL FE.

Why? Because this is the result of many years of research.

Lyn,

thanks, could you ellborate the reason it should work over other possible coating materials on the seat.

You really should learn how to use a search engine!

PLASMA-ARC HARDFACING EXHAUST VALVES WITH AN IRON ...

the link does not justify this alloy for CNG though, it might be good for Gasoline. Well my usage of search engine gave me a different result!!

since this is a less oxidising atmosphere, just any composition will not help. You need to have a special composition to work on which can give good wear resistance when there is less scope of oxidation on the surface as compared to a Gasoline engine.

In such case you need higher Mo and less Cr, thats for sure.

munish, you are on the right track. CNG burns totally different than gasoline. The tribology valve or an Inconel valve is the best for this application. If you know a good engine specialist in the natural gas pipeline industry that would be your best bet for technical data. If someone is telling you that it is the same as gasoline they are completely wrong and know nothing of the natural gas business.

Like Lyn said.

If the valves in a regular gasoline burning engine are made from the right stuff in that application then it should be fine for lower energy fuels like CNG.

Why do you need to know this?

Wal,

I tried coating these valve seats with St-6, St-F but none worked. The final work as with Tribaloy 400 one of the best alloys for a dry CNG atmosphere. Though customer has not expressed satisfaction...the lab trials were success...though on field it failed....reasons under investigation

I guess I don't understand your problem. You initially inquired about a valve coating to be used in a CNG powered engine. In this post you talk about valve seat test results. Which is it, and can you describe the failure modes you have experienced with the materials you have tried? Norton (St. Gobain) has made ceramic valves that stand up to any high temperature atmosphere you can dish out, but they tend to be brittle.

Sorry that was a miss...the valve - seat area is what I meant called mostly as the valve head - to be coated for wear resistance.

the mahor problem is with corossion and compression loss.