The studies were performed on D3 tool steel hardened after austenitizing at 1050°C during 30 min and tempering at 200-700°C. Based on the diffraction studies performed from the extraction replicas, using electron microscopy, it was found that after 120-min tempering in the consecutive temperatures, the following types of carbides occur:Apart from higher mentioned carbides, there are also big primary carbides and fine secondary M 7 C 3 carbides occurring, which did not dissolve during austenitizing.

carbides behavior in the steels of 2 pct C ϩ 12 pct Cr ϩ additives type in temperatures slightly lesser than solidus 1. G.R. Purdy: Met. Sci. J., 1971, vol. 5, pp. 81-85. temperature. In Reference 6, it was stated that during austeni-2.

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The main purpose of the studies was to establish the effect of the tempering temperature on the changes of carbide and retained austenite contents. It has been found that the course of changes of the coercive force of hardened steel after austenitizing is qualitatively similar to the hardness changes. That means in practice it is possible to determine the 217H12WF steel hardness based on the measurement of the coercive force.

The paper presents the study results on chemical composition of the coarse primary M 7 C 3 carbides occurring in the soft annealed NC11LV/D2 tool steel consisting of: 1.53% C; 11.65% Cr; 0.01% W; 0.81% Mo; 0.068% V; (balance iron plus admixtures), used for cold operation. The microanalyzer of type SEMPROBE Su-30, French made by CAMECA Co., equipped with two WDS X-ray spectrometers and an EDS VOYAGER 3 100, NORAN Instruments Co., made in USA. It was found that out of the three alloying elements occurring in the big carbides of the annealed NC11LV/D2 steel, i.e. Cr, Mo, and V, the chromium appears to be the most uniformly distributed. The big carbides vary concerning C, Cr, Mo, V; the greatest differentiation degree of the contents of Mo and Cr, and the least -of vanadium. The average chemical composition of the big/coarse carbides is as follows: C = 9.42±1.28%; Cr = 44.17±2.95%; Mo = 4.48±3.52%; V = 4.53±0.31%; balance Fe.