Influence of the chemical composition of the matrix on the structure and properties of monolithic SHS composites

OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 23 No. 3 2021 Fig. 2. Morphology and distribution of particles of strengthening TiC and TiB 2 phases in the studied SHS composites: a – Fe matrix; b – Fe + Ni; c – Fe + Ni + Cr; d – Cu а b c d areas of chromium ferrite were formed in the matrix (indicated by the number 2 in Fig. 5, a ). Chromium is also involved in the formation of Cr 23 C 6 carbides, which are separated along the boundaries of austen- itic grains (thin layers enriched with chromium, in Fig. 5, c ). Titanium carbide and diboride particles are formed mainly in a solid solution based on Ni (Fig. 2, b and 5, d , e ). The composite is quite dense, single micropores with a maximum size of 5 µm are recorded, located mainly between clusters of TiB 2 particles. Phase X-ray diffraction analysis showed the presence of Ni 3 Ti intermetallide, as in the composite of com- position 2. The hardness of the composite of composition 3 was 66-72 HRC, and the bending strength R bm 30 = 670 MPa (Table 2). Melting temperature of copper (1,083 °С) is significantly lower than iron (1,538 °С), chromium (1,907 °С) and nickel (1,455°С). In this regard, with the same thermal effect of the SHS process of all the studied powder compositions (the content of TRC in the mixture is the same), we should expect significantly dif- ferent conditions for the formation of the composite structure. Amicro-X-ray spectral study of a composite with a copper matrix obtained from a powder mixture of composition 4 (Table 1) revealed the presence of