Fabrication and Microscale Characterization of Iron Matrix Composite Wires Reinforced by in situ Synthesized Iron Boride Phases

For decades, the demand for thermally stable wear and corrosion-resistant materials has been met by surface boriding of ferrous materials. Issues associated with the surface boriding, such as boride layer-host material interface instabilities, could be avoided by the in situ synthesis of iron borides. However, attempts to fabricate bulks of iron matrix reinforced with iron borides using casting have inherent drawbacks. The requirement of elevated temperatures and less control over the microstructure can be given as examples. This study uses an in situ approach to manufacture iron matrix microcomposite wires reinforced with controlled morphology and ratio of iron borides. Powder mixtures of 5, 10, and 15 vol. %similar to B4C in Fe are compacted in steel tubes which are cold rolled to turn the iron particles into extended fibers. Wires are later treated at 1100 degrees C for 2 h to assist the B diffusion into elongated Fe particles, consequently resulting in the synthesis of iron borides. The influence of the processing parameters on the microstructure is evaluated using microhardness, SEM, EDS, tensile testing, and fractographic analyses. Results showed that the iron borides' morphology and relative ratio in the iron matrix can be controlled by employing an appropriate combination of plastic deformation and powder mixture ratios in the pre-sinter wires.