Choice of materials for operation in an abrasive-laden air stream

Abstract

1. The wear resistance of steel subjected to the abrasive action of a gas stream depends on its hardness and structure and on the angle of attack. For each type of structure, there is a characteristic dependence of wear intensity on the angle of attack and hardness at a constant angle of attack. The relationship is linear within the limits of this type of structure. 2. In a stream of solid particles at angles of attack of up to 60°, lamellar structures are less wear resistant than the tempering products of martensite; at angles of attack exceeding 60°, the position is reversed. The optimum heat treatment for steel subjected to combined wear is quenching with subsequent high-temperature tempering at 400–600°C; in the case of wear induced by a stream of the impact-sliding type, the optimum heat treatment consists of quenching to martensite and subsequent tempering at 200°C. The wear resistance of each structure in a stream of the impact-sliding type is determined by the dispersion of the structural constituents and grows as the dispersion is increased. The reverse is true when contact between solid particles and the specimen surface takes place under impact conditions. 3. The strongest influence on the wear resistance of steel is exerted by its carbon content. At angles of attack of up to 60°, carbon increases the wear resistance at tempering temperatures of up to 400°C and decreases it at higher tempering temperatures. 4. Stainless steels of the martensitic type are only slightly superior to carbon steels in wear resistance, and should therefore by used only where there is a danger of corrosion attack by chemically active media.