A boron-rich boron–carbide material (B4+δC) was synthesized by spark plasma sintering of a ball-milled mixture of high-purity boron powder and graphitic carbon at a pressure of 7 MPa and a temperature of 1930 °C. This high-pressure, high-temperature synthesized material was recovered and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, Vickers hardness measurements, and thermal oxidation studies. The X-ray diffraction studies revealed a single-phase rhombohedral structure (space group R-3m) with lattice parameters in hexagonal representation as a = 5.609 ± 0.007 Å and c = 12.082 ± 0.02 Å. The experimental lattice parameters result in a value of δ = 0.55, or the composition of the synthesized compound as B4.55C. The high-resolution scans of boron binding energy reveal the existence of a B-C bond at 188.5 eV. Raman spectroscopy reveals the existence of a 386 cm−1 vibrational mode representative of C-B-B linear chain formation due to excess boron in the lattice. The measured Vickers microhardness at a load of 200 gf shows a high hardness value of 33.8 ± 2.3 GPa. Thermal gravimetric studies on B4.55C were conducted at a temperature of 1300 °C in a compressed dry air environment, and its behavior is compared to other high-temperature ceramic materials such as high-entropy transition metal boride. The high neutron absorption cross section, high melting point, high mechanical strength, and thermal oxidation resistance make this material ideal for applications in extreme environments.
Selective laser melting of Ti6Al4V-B4C-BN in situ reactive composites
An increasing desire for higher application temperatures and complex geometries for metallic materials has spurred significant development in additive manufacturing (AM) of metal-ceramic composites; however, limited process-microstructure-properties relationships exist for these materials and processing strategies. Herein we investigate the processing window and high-temperature oxidation performance of an in situ reactive, oxidation-resistant titanium metal-matrix composite reinforced with boron nitride (BN) and boron carbide (B4C) via selective laser melting (SLM) to understand the effects of processing parameters on the in situ reactive characteristics and their effects on build reliability and high-temperature oxidation performance. SLM processing required a 50% decrease in overall energy density relative to titanium's optimal parameters to avoid processing failure due to the high in situ reactivity and exothermic reaction between feedstock materials. A precise balance was necessary to combine decreasing the input energy to avoid cracking due to in situ reactivity while simultaneously providing enough input energy to keep the bulk density as high as possible to limit porosity that contributes to processing inconsistencies at low input energy. Process optimization resulted in composites with as high as 98.3% relative density, comparable to some of the best composites reported in the literature, and high-temperature oxidation testing revealed a 39% decrease in oxidation mass gain compared to Ti6Al4V, owing directly to ceramic reinforcement. Our results indicate that control of SLM processing parameters can yield advanced composites with enhanced properties and characteristics compared to the base material, revealing an array of design possibilities for researchers and engineers in many fields.
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- Award ID(s):
- 1934230
- NSF-PAR ID:
- 10354350
- Date Published:
- Journal Name:
- Journal of materials research and technology
- Volume:
- 18
- ISSN:
- 2214-0697
- Page Range / eLocation ID:
- 2654-2671
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/doi.org/10.1016/j.jmrt.2022.03.092
