Production of boron-containing powder steels using master alloys and boron carbide

The properties of boron-containing structural powder steels produced using master alloys and boron carbide are examined. It is established that sintered and thermally treated materials produced with master alloys show better mechanical properties than those made with the use of boron carbide. The boron content of structural powder steels that promotes the optimum combination of properties with the use of master alloys with different compositions is about 1.2%. steels with the use of master alloys with several compositions. Boron-containing powder master alloys were synthesized from mixtures of iron and boron carbide powders with different compositions that were compacted to form briquettes to be sintered at 1050-1200°C. The synthesized (sintered) porous briquettes were ground in a planetary mill. Powder master alloys with three compositions (Table 1), produced by thermal synthesis at 1100°C, were used to make boron-containing (0.4, 0.8, 1.2, and 1.6% boron) iron-based powder materials. Each master alloy was used to make materials with the same composition (Table 2). It is obvious that the higher the boron content of the master alloy, the smaller amount of the latter will be required in the charge to produce materials with a specific composition. Reference samples were made of iron powder mixtures containing 0.5, 1.0, 1.5, and 2.0% boron carbide; hence, the boron content of sintered materials is the same as after the use of master alloys. The samples 10 mm in diameter and height were compacted at a pressure of 800-900 MPa and sintered in a melt-sealed container (3) at 1080 and 1150°C for 2 h. Some samples were water-quenched at 1000°C and then subjected to low-temperature tempering at 250°C for 3 hours. We measured the density and porosity of the samples before and after sintering, diametrical linear shrinkage, hardness after sintering and heat treatment, and compressive strength. In addition, all the materials were examined with metallography.