Nimonic compound exhaust valve spindles for diesel engines via hot isostatic pressing

Until the present time the materials used for exhaust valve spindles for diesel engines have comprised a main body of heat resistant austenite steel with a Stellite layer covering the seat area. Recently, to satisfy increasing demands for higher efficiency of engines, a forged Nimonic 80 exhaust valve spindle has been developed. This valve spindle has higher strength and hot corrosion resistance than conventional austenite steel valves. This paper introduces a compound type Nimonic 80A-austenite steel valve spindle produced via hot isostatic pressing. Nimonic 80A powder metal is consolidated and diffusion bonded to an austenite spindle body. The seat area and the total combustion chamber side of the spindle are clad using Nimonic 80A. The compound valve spindle produced via hot isostatic pressing has the same performance as a forged Nimonic 80A spindle and in addition it has improved repair weldability and hot corrosion resistance compared with the forged Nimonic 80A spindle valve. Because less of the expensive Nimonic 80A material is used, there is an added advantage in that the cost of the valve would be cheaper. Successful engine test results are also described