A model of diffusion growth of carbide-phase particles in the carburized layer of heat-resistant steels

Abstract

A mathematical model of carburization of a complexly alloyed heat-resistant steel is suggested for predicting the chemical and phase composition and structure of diffusion layers that allows for formation of particles of the excess carbide phase in the carburization process. A computer-aided solution of the set of nonlinear equations makes it possible to compute the distribution of the carbon concentration, the volume fraction of the carbide phase, and the distribution of its particles over the thickness of the diffusion layer.

Failure analysis of the piston used in a pneumatic down the hole impactor

“…Prior research has shown that after the carburization of the piston at 850 ℃ for 10h, carbides may be also be formed in the carburized layer [10][11][12] . Figure 5 shows two kinds of carbides precipitated in the carburized layer.…”

“…Osman et al [7] investigated the fatigue fracture and found that the fatigue crack originated in the carburized layer's intergranular fracture region. During the carburizing process, the carburized layer of steel will form carbides such as Fe3C, M23C6, M6C and M7C3 [8][9][10][11][12] . Kenzo [13] observed that the carbide fracture in the carburized layer is the cause of fatigue crack initiation and that the fatigue life of the material can be improved significantly by volume reduction of primary carbides.…”

Determination of the coefficient of carbon diffusion for calculating nonisothermal regimes of high-temperature ion nitrocarburizing

“…Relation (9) makes it possible to obtain an expression for the coefficient of carbon diffusion over linear defects of the crystal structure with help of formula (2), i.e., In order to check the obtained dependences we compared the concentration curves calculated with the help of the mathematical model of [5] employing expressions (l), (10) and plotted from experimental data. As an example, we present the results of such an analysis in Fig.…”