What do you think about machining the inside of the prechamber to allow the shield to be installed ? Do we need a CNC or a simple milling can do the job ? As you are the expert in machining..
but I wonder how thick the material would need to be in stainless or inconel to have an equivalent thermal barrier as a ceramic coating would provide?
Zirconium Oxide CoatingZirconium oxide coating was developed for the space industry. When applied to aluminum it reduces heat transfer, as a result of the lower heat conduction of zirconium oxide (0.53 BTU/hour/feet) compared with the heat conduction of aluminum (139 BTU/hour/feet). The coating is applied using a special process that mixes powedered zirconium oxide with superheated plasma gas that is sprayed onto the aluminum. The coating, which also goes by the name of Turbokoting, is three layers thick, adding a substantial 0.015 to 0.018 inch to the surface.If you are under budget on your engine work, Turbokoting is for you. Pistons cost about $50 each to coat, and the cylinder head will run about $300. For this reason, I recommend this only for highly stressed turbo motors, and then only if the coating is properly applied.So far there have been no real problems with the coating flaking off and destroying the turbo (although any coating of this type has the potential for doing so), but it is a good idea to take some 220- or 320- grit sandpaper and lightly scuff the finished coating.Another reason that this does no get an unqualified okay is that it does not remove of reduce the heat of combustion, it just keeps it from soaking into the coated surface. This heat still has to go somewhere. In a turbo motor, if you can get it all going out the exhaust port you will have better turbo efficiency and better throttle response. The problem is that some of the heat also gets to the rings, the cylinder walls, the valves, and so on.For less than an all-out motor, you probably will not want to get involved in the research and development it would take to discover the pros and cons of using this coating in your application.
Quotebut I wonder how thick the material would need to be in stainless or inconel to have an equivalent thermal barrier as a ceramic coating would provide?I am unable to find any real information on the thermal conductivity of ceramic coatings. The websites give info in terms of skin temperature drop when used on exhaust headers, virtually no engineering data or hard numbers. Kinda disappointing for an industry that claims to be high tech... Inconel has a thermal conductivity of 1/10 that of cast aluminum, depending on the alloy. Thermal conductivity of 356 aluminum alloy (typical cast) is 128 W/m K, inconel is 12 W/m K. It is my belief that most ceramics are aluminum oxide based, ALO has a thermal conductivity of 30W/m K or 2.5 times better (worse?) than inconel. I wish I could find figures for the actual ceramic coating...