Thermal synthesis of Fe–B4C powder master alloys

Abstract

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

Crystalline potassium dihydrogen phosphate (KDP) powders

“…Of course, the main role in the properties of a nanomaterial is played by the type of system, which can be single-component [74][75] or multicomponent [76][77][78][79]. No less important is the technology of preparation [80][81][82][83][84][85] and processing of the material before its use, which confirms the theoretical [90][91][92] and experimental [93][94][95][96][97][98][99][100] data.…”

Effect of B4C on wear behaviour of ZTA ceramic reinforced high chromium cast iron matrix composites

“…At the same time, the element distribution of Fe and Cr were relatively less in the composite layer, and the B element was more uniform, which meant that B 4 C can be reacted or decomposed under the action of molten iron. B 4 C reacted with elements of groups 4, 5 and 6 in the periodic table and formed the of metal borides at 1000°C to 1100°C, the metal elements in HCCI were mainly distributed in these groups, some chemical reactions changed the distribution of elements in the ceramic [10-12]. During the infiltration process, B 4 C would react as follows [13]:

Figure 7 (a) Pattern and (b) results of line scanning across composite interface.

…”

“…At the same time, the element B had a small atomic radius and dissolved in the ceramic particles and iron matrix. The elements penetrated each other in the matrix and the reinforcement, which further promoted the metallurgical bonding between the two [12,13].…”

Solubility of hydrogen in metals and their alloys

“…де R -газова постійна. Знаючи теплоти розчинення λ A , λ B атомів С в чистих компонентах А і В, можна оцінити енергетичний параметр (11), що входить у формулу (9) для розчинності.…”