The increase in the strength of teeth of carburized and carbonitrided gears

Abstract

1. In carburizing and carbonitriding of alloy steels (Cr, Cr−Ni−W, Cr−Mn−Ti, Cr−Mo, Cr−Ni−Mo, Cr−Mn−Mo) a surface layer is formed consisting of decomposition products of austenite in the pearlitic or intermediate region (the result of internal oxidation of alloying elements and inclusions of submicroscopic carbonitride inclusions). 2. The depth of the layer with a structure of nonmartensitic decomposition products and its hardness depend on the composition of the steel and the cooling rate during quenching. In steels containing molybdenum the decomposition products have a higher hardness. 3. The fatigue strength in bending of carburized and carbonitrided gears depends on the microhardness of the surface in the valleys of the teeth and increases with the microhardness. 4. In alloying of steel intended for carburizing and carbonitriding one must keep in mind the susceptibility of alloying elements to internal oxidation and formation of carbonitrides.