engleski

EFFECT OF CARBON THERMODYNAMIC ACTIVITY IN STEELS ON BORIDE LAYER GROWTH

Case hardening by boriding entails the treatment of steels in a boriding atmosphere at a high temperature. This heat treatment is one of the most important technique to improve the mechanical properties such as load carrying capacity, abrasion, hardness, wear, impact strength of the steels. In this paper, kinetic studies of Boride layer growth on five steel samples namely W. Nr. 1.1141 (0.15% C), W. Nr. 1.0503 (0.45% C), W. Nr. 1.7131 (0.16% C, 1.1% Mn, 0.9% Cr), W.Nr. 1.0904 (0.55% C, 1.7% Si) and W.Nr. 1.5919 (0.15% C, 1.5% Cr, 1.5% Ni) were established. All the samples are placed in a square retort such that each sample is well exposed to the boriding medium DURBORID G and heat treated at a temperature of 900ᵒ C for 6 hours after preheating the muffle furnace for 50 minutes. The morphology and depth of borides formed were confirmed by optical microscopy. This experiment enabled the study of boron diffusion mechanism with respect to the activity of carbon. Results confirmed that the activity of carbon of each sample varied because of difference in the alloy composition of the steel and this affected the growth of the boride layer. Attempts were made to draw a relation between activity of carbon and the boride layer growth. The experimental results are compared and verified with the algorithm of sophisticated computer program.

boriding, thermodynamic activity, boride layer growth, diffusion, case hardening

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