The Influence of Sintering Temperature and Content of High-Carbon Ferrochrome on the Structure and Properties of Iron–FKh800  Powder Composite Materials

O.M. Gripachevsky,
M.I. Podoprygora

I. M. Frantsevich Institute for Problems of Materials Science of the NAS of Ukraine, Omeliana Pritsaka str.,3, Kyiv, 03142, Ukraine
Powder Metallurgy - Kiev: Frantsevich Institute for Problems of Materials Science NASU, 2021, #03/04


The influence of sintering temperature and content of high-carbon ferrochrome on the phase composition, structure, and mechanical properties of powder chromium carbide steels was studied. With sintering temperature increasing from 1100 to 1250 °C, the bulk shrinkage, density, porosity, hardness, and bending strength of iron-based composites with high-carbon ferrochrome FKh800 content varying from 25 to 40 wt.% increase nonmonotonically and porosity decreases. The optimal sintering regimes for the Fe–(25–40 wt.%) FKh800 composites were established and the FKh800 content in the composition range under study was found to hardly influence the optimal sintering temperature of the composites. A vertical cross-section was constructed by the analytical/graphical method, which demonstrated wide regions of (γ-Fe) + (Cr, Fe)7C3 and (α-Fe) + (Cr, Fe)7C3 two-phase equilibria. The constructed vertical cross-section allowed us to find that the eutectic composition was 73.7 wt.% Fe–26.3 wt.% FKh800 and the eutectic formation temperature was 1285 °С and tentatively determine the most suitable sintering range for the iron-based composites with FKh800 content varying from 1100 to 1250 °С. Electron microscopy studies of the carbide steels showed that their microstructure was heterogeneous and consisted of metallic and carbide phases and a number of pores. According to electron microprobe analysis and X-ray diffraction of the carbide steel, its metallic phase was close in composition to Kh17 chromium steel and the carbide phase corresponded to (Cr, Fe)7C3 carbide. The effect of high-carbon ferrochrome content in the 25–40 wt.% range on the mechanical properties of the composites was studied. When FKh800 content increased from 25 to 35 wt.%, the hardness and bending strength and the crack resistance reduced. The optimal combination of these mechanical properties was shown by 65 wt.% Fe–35 wt.% FKh800 carbide steel.