Valve made by joining together two different valve materials by friction welding wherein high hot hardness alloy steel (austenitic steel) is used at the head and the stem made from an upright mechanical properties steel (martensitic steel). In this way a better usage of the properties of each material is achieved, high temperature corrosion resistance in the austenitic stainless steels of the head, and high tensile strength and abrasive wear resistance in the martensitic stainless steel of the stem. This technique is used in medium to high stressed exhaust valves and in high stressed intake valves.

A small piece of martensitic steel is welded on the stem end when the entire valve is manufactured in stainless steel (non-quenchable). This is done to increase the impact and ware resistance of the stem end. Then, this tip is quenched to improve their mechanical properties.

To improve the corrosion and high temperature ware resistance, mainly in exhaust valves, a cord of special material is placed onto the valve seat. Valves made by using deposit of stellite to get high hot hardness at the seat. The special material is generally a cobalt base alloy (called Stellite), although it can also be iron or nickel base.

Through an electromechanical process a layer of hard chromium is stored over the stem. The thickness of this layer generally will depend on the level of the piece stress. The main function of the chromium layer is to reduce the friction between the stem and the valve guide, and to store among its micro-cracks, small amounts of lubricating oil. All this results in better operating conditions increasing. Therefore the useful life of the valve guide and stem

Nitride Engine Valve with the ultimate solution for valves that are intended for use in highly corrosive environment. The Nitride coating will substantially reinforce the valve’s corrosion resistance property and enable highly durable valve performance. The tuffen Nitride Process will also provide enhancement to the valve’s ware resistance property, significantly increase the valve’s lifespan, and improve the valve stem friction coefficient to allow decreased friction between the stem and the valve guide. Nextech recommends on Nitride coating for valves that are due to perform in extremely high corrosive environment, be it for any kind of engine that outputs such conditions. The Nitride coating is presented in Grey and black colour.