Stainless steel valves

[Stephen Lamb]

>I think you mean Titan-nitrid coated (once seen in a Harley sportster)
>They have a golden-looking finish.

Titanium Nitride is wear resistant coating now commonly found on cutting
tools, etc.  It is quite a thin coating, really.  Stellite (cobalt based
alloy) is an alloy more commonly used for valve seat faces.

> The best currently used valve material is "Inconel", once
>used in Bell's X-15 aircraft (or rocket?)
>to resist air-friction at Mach 23 and more. It is temperatur stabil
>up to 1200 C.(I hope I remember right). Today they use it for
>race car exthaust-pipes and big-diesel valves. It contains more
>then 50% of nichel. (Our metallurgist would know exact values?)

Inconel is actually a brand name for a range of Nickel based 'super alloys'
(eg Inconel 718), but there are also iron and cobalt based super alloys
(examples being Incoloy 800 and Stellite 6B respectively).   1200C is right
at the upper limit for the conventional super alloys and at these
temperatures no significant load could be carried.  Generally, 950C is
regarded as the upper limit for load carrying applications.   These
materials form the bulk for application in aircraft gas turbine hot end
components (eg combustion cans, turbine blades, etc.).   These materials
are *very* expensive and their use in ICE's of any description would be
rare to say the least (the Stellite application to valves is the only one I
can think of).

>TiN-coating a valve has similar functions as hard chroming.

In the sense that it is basically a coating for wear resistance, yes.

Cheers

Stephen Lamb
Dept. of Defence DSTO, AMRL
506 Lorimer Street
Fishermans Bend  VIC  3207 Australia
Tel: +61 3 9626 7525
Fax: +61 3 9626 7089

IZCC #180