The paper examines the thermal synthesis of master alloys from a mixture of iron and boron carbide powders. It is shown that the content of boron decreases as compared with the starting mixture and the boron/carbon ratio in the master alloy powder changes with increasing synthesis temperature. Thus the initial content of boron carbide in the mixture insignificantly influences the boron/carbon ratio after sintering. At the same time, the content of boron carbide in the mixture and synthesis temperature essentially influence the structure and phase composition of the master alloy obtained.Iron-based boron-bearing alloys attract researchers' attention as they have high hardness, strength, and wear resistance and are relatively cheap. They can be thus regarded as promising materials for structural wearresistant alloys [1][2][3].Boron carbide is the most effective boron-bearing element for alloying powder steels [4]. At low temperatures (1050-1150°C), it actively interacts with iron to form solid metallic compounds (iron borides and carboborides), which harden the material. The interaction of boron carbide particles with iron when compacts are sintered yet involves secondary porosity, when pores form instead of original B 4 C particles [4].The solubility of boron in iron is very low (up to 0.08% [3]), and the introduction of small additions of boron is challenging since it needs to be uniformly distributed over the charge.Powder materials are much easier doped if master alloys are introduced into the charge instead of elementary powders mixed; in addition, such sintered materials usually have higher strength and plasticity [5]. The secondary porosity should obviously be prevented in using boron-bearing master alloys.The production and use of boron-bearing powder master alloys have hardly been examined. The objective of this paper is to examine the synthesis, chemical and phase compositions, and structural state of Fe-B 4 C master alloys with high content of boron carbide.Master alloys with different compositions were produced as follows. Iron powders of PZhRZ.160.28 grade (GOST 9849-86) were mixed with 6-15 wt.% boron carbide (20.7% C and 77.2% B) with particles smaller than 63 μm in a drum mixer for 1 h. The mixtures were pressed under 400 MPa into porous briquettes, which were sintered in a muffle furnace for 1 h at 1050, 1100, and 1200°C in a melt-sealed container. To displace excess air and create reducing media in the container, about 2% paraffin shavings (relative to the mass of the backfill) were added to the backfill (calcined alumina). After thermal synthesis, the samples looked like a porous sponge with typical

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The influence of the temperature of heating for drop-forging on the fine structure of the ferrite of powder steel Kh17 is investigated. On the basis of structural characteristics obtained from different drop-forging sites by means of harmonic analysis, substantial differences in the degree of structural defectiveness in the crystal lattice between the outer faces and an internal layer of the samples has been established. The highest degree of structural defectiveness is found in the structure of the outer faces following heating for drop-forging to 1050°C while a uniform structure throughout the drop-forging volume is created following heating to 1100°C.Keywords: porous green body, heating temperature, drop-forging, deformation, structural defectiveness of crystal lattice.It is well known that alloying of steels with chromium leads to refinement of the grain and an increase in hardness, strength, and wear resistance [1] as well as to heterogeneity of the structure of powder steels obtained by means of hot drop-forging [2]. Moreover, the fact that such steels are prone to self-hardening affects the evolution of its structure [1]. The slow development of the processes of softening in steels that have been alloyed with chromium is related to the difference in the diffusion constants and the retarding influence of carbide inclusions [3].Chromium steels containing 17% Cr and a small quantity of carbon belongs to the class of semiferrite and ferrite steels in which a γ → α transformation occurs only in one phase or does not occur at all [1]. The entire spectrum of structures is observed in chromium steel that has been sintered of a mechanical mixture, from ferrite to troostitemartensite [4]. The hardness of the base may vary from 1.02 to 6.52 GPa. The properties of semiferrite steels depends on the ratio between the γ and α phases. It has been noted that cracks appear as the carbon content is increased upon rapid cooling of steels [1] containing 17% Cr. Moreover, the properties of powder chromium steels depend to a significant extent on the method used to add the chromium and the type of structure that forms as a result. The production of chromium steels out of alloy powders leads to the creation of the most homogeneous structure [5].Kh17 alloy chromium powder produced by diffusion saturation from point sources is the starting material for fabrication of green body with porosity of about 15% [6]. The porosity of the drop-forged pieces following heating to 950, 1000, 1050, 1100, and 1150°C for 15 min amounts to 3.96, 3.33, 2.68, 2.94, and 2.5%, respectively.The chemical composition of the samples following forging in the temperature interval 950-1150°C is presented in Table 1. The carbon content in the drop-forged pieces is basically 0.11-0.12% while that of chromium, 17.9%. The chemical composition of the sample following heating for drop-forging to 1100°C is slightly different, with the carbon content down to 0.10% and the chromium content down to 17.8%.The intragranular structural defectiveness of Kh17 powder steels ...