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

Abstract

Introduction. The development of new wear-resistant materials obtained by the method of self-propagating high-temperature synthesis (SHS) is an urgent problem in materials science. The SHS method is most widely used in the field of creating new powder materials. Much less attention has been paid to the production of monolithic non-porous composites. For monolithic composites, it is very important to identify the role of the metal matrix and phase transformations in the process of secondary structure formation after the completion of the synthesis process when the obtained material is cooled. The aim of this work was to carry out a comparative analysis of the structure and properties of SHS composites of the Fe-Ti-C-B, Fe-Ni-Ti-C-B, Fe-Ni-Cr-Ti-C-B, and Cu-TiC-B systems. Materials and research methods. Composites were obtained from powder mixtures consisting of thermoreactive components Ti, C, and B, as well as matrix Fe, Fe-Ni, Fe-Ni-Cr, and Cu. The initial powders were thoroughly mixed, loaded into a steel tube container, and the powder mixture was preliminary compacted. Then, the workpieces were heated in an electric furnace to the temperature of the onset of autoignition. After completion of the SHS, the workpieces were deformed with a force of 250 MPa in a hydraulic press at a temperature not lower than 1000 ° C. Samples were cut from the obtained sandwich plates for microstructural studies, density determination, hardness measurements, transverse bending tests and abrasive wear resistance tests. Results and discussion. All investigated composites were characterized by an uneven distribution of strengthening particles TiC and TiB2 over the volume. The use of the Fe-Ni matrix led to the formation of regions with the γ-Fe + Fe2B eutectic structure in the composite and an additional strengthening phase Ni3Ti. The use of Fe-Ni-Cr metal-matrix components led to the formation of two solid solutions in the matrix - austenite and ferrite, and Cr23C6 particles were formed along the boundaries of austenite grains. The maximum transverse bending strength was shown by SHS composites of the Fe-Ti-C-B and Cu-Ti-C-B systems with a matrix of FCC solid solutions. All composites had a hardness of 66 -72 HRC and showed the same abrasion resistance.