Valve materials and design

Abstract

Materials for engine valves have been largely standardised throughout the world, not by force of international agreement, but because the most widely used alloys have presented an excellent balance of cost, mechanical properties, and corrosion resistance. Although engine operating temperatures and pressures are increasing steadily, improvements in manufacturing processes and application engineering have more than kept pace, so that valve durability is at least equal to that of other mechanical components in the engine. Properties of valve steels are described and design details discussed. The practice of overlaying exhaust valve seat faces with Stellite or the newer iron based facing materials using the plasma transferred arc process is described. The development of cost effective methods for surfacing valve stems to minimise wear is considered.