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Valve seat material for CNG engines!

Valve seat material for CNG engines!

Valve seat material for CNG engines!

I followed many activities for selecting a suitable material for valve seat inserts (especially exhaust) of a CNG-Bifuel engine, Following materials were selected, sampled and tested through engine durability procedures:
1- a cast Ni-resist (nickel added) heat resistance cast iron with impregnated copper alloy, this alloy is made and developed especially for VSI, but unfortunetely the engine failed because of seat sever wearing and the material could not pass the test.
2- a sintered Co-Mo die steel alloy with rare content of chromium and nickel alloys that had a good hot hardness and radial crush strength for CNG engine application, but this alloy also had heavily amount of non homogenious wearing and scuffings on valve contact faces.
3- an improved Co-Mo-Tungsten-Vanadium tool steel with excellent hardness-wearing specifications, we tested this material as the exhaust valve seat insert and same as the other materials, this alloy failed.
now, I am working on new cobalt or nickel base alloy because the previous results showed me that base iron alloys can't withstand thermal-mechanical-corrosion conditions of this CNG-Bi fuel engine.
any idea can point me into right direction is welcome.

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