Investigation of the Structure of Sintered Blanks from Powder Mixture of R6M5K5 High-Speed Steel Containing Diffusion-Alloyed Powder

The paper draws attention to the existing problem of the formation of a defect in the form of a carbide network in cast high-speed steels, which makes products made of such material susceptible to brittle fracture during their operation. The paper also points out high hardness of the particles of pulverized high-speed steel powders, which is why compact products made of these powders are currently obtained by a technologically complex method of hot isostatic pressing. As an alternative to such a powder, a powder mixture of R6M5K5 grade steel is considered, which contains a diffusion-alloyed spongy powder based on tungsten, molybdenum, cobalt, and iron, and can be compacted by cold pressing. A study of the structure of a billet made of such mixture and sintered at 1,000°C revealed the formation of fine-sized carbides, which takes place inside the iron matrix both between and within the grains. Such carbides have a needle-like and flaky shape. Their presence has a positive effect on the hardness of the products. The structure of a billet made of a smaller-fraction powder and sintered at 1,200°C was denser and had finer grains; however, carbides were larger in size and were located as separate inclusions in the structure. It is noted that by selecting the optimal particle size distribution of the powder mixture, compaction pressure, temperature, and soaking time during sintering and subsequent heat treatment, it becomes possible to obtain high-density blanks with fine-grained homogeneous structure.