In previous articles we have looked at the various materials used for valves, and examined some of the relative merits of these materials. The ’super-alloy’ materials are particularly suited to high-temperature applications, having been developed initially with a view to use in gas-turbine engines. But they are relatively heavy.
Titanium is much more favourable in terms of component mass, and is widely used in motor racing. The material comes with problems though; titanium requires surface Read more…
So far in Race Engine Technology’s coverage on valves, there have been a number of articles on valve materials for the more extreme applications, specifically pieces on 
In racing valvetrains, there is always an imperative to reduce reciprocating mass, as it allows the valvetrain engineer to be more aggressive with his cam profiles in an attempt to improve the valve lift curve, by increasing lift, increasing the area under the curve and so on. This will generally require greater valve acceleration or deceleration.
In the previous article on this subject we looked at the use of Inconel as a valve material. This month I’ll look at an application of another high-temperature valve material, Nimonic alloys.
In the last article, the author looked briefly at the kinds of materials that we might use for high specific output applications such as supercharged or turbocharged engines. In the article we mentioned a couple of the popular ’superalloys’ which are used for poppet valves, namely ‘Nimonic’ and ‘Inconel’ alloys. Although not as widely used as the Nimonic materials, Inconel is used in the same sorts of applications, and Wayne Ward recently discussed its use as a valve material with Californian-based Supertech, a leading valve manufacture specialist who uses this material. 
In a previous RET Monitor articles, we have looked at a couple of valve materials, namely titanium and titanium aluminide. The chief advantage of these materials is their low density which has obvious appeal when trying to keep control of valves at increasing engine speeds. Titanium aluminide, besides being possessed of even lower density than titanium has the additional advantage of increased stiffness, making it an excellent choice for poppet valves. 
There are a number of coating companies offering thermal barrier coatings, and some claim that internal combustion engine valves are an ideal candidate for these types of coatings. There are many whose advertisements target the racing community in particular.
The tip of the racing poppet valve is seldom considered, despite having to withstand relatively high contact stresses. Whilst we can say that the contact stresses concerned are generally low compared to other valve train applications, the relative movement between the valve tip and the adjacent component can be low, especially in the case of overhead cam engines where a lash cap or, more rarely, a bucket follower applies the load to the valve.
In recent articles, we have assessed some of the materials employed in the manufacture of racing valves. This month we will take a break from this recent theme, and take a brief look at some of the surface treatments used on racing valves, perhaps returning in the future to look more deeply at some of them. 
