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The slurry and sol‐gel methods were used to introduce SiC nanowires (SiCnws) into the SiCf/HfC‐SiC composites. The microstructures, ablation, and bending behaviors of the SiCnws modified composites prepared by the two methods were compared. The bending strengths of the modified composites obtained by introducing SiCnws by the slurry and sol‐gel methods were 224 ± 19 and 154 ± 14 MPa, respectively. The results showed that SiC fibers with chemical corrosion and thermal damage during the sol‐gel process decreased the bending strength of the SiCnws‐modified SiCf/HfC‐SiC composites. Meanwhile, the pyrolytic carbon interface accompanying corrosion damage in the sol‐gel process led to the degradation of interface function, which hindered the interface debonding and fiber sliding of the composites during the bending test. After ablation, the bending strengths of the two composites were 188 ± 19 and 50 ± 7 MPa, respectively. The bending strength retention of the modified composites fabricated by the slurry method (83.9%) was higher than that (32.5%) of the composites fabricated by the sol‐gel method after ablation. As the composites fabricated by the slurry method exhibited a good ablation resistance under the oxyacetylene flame (∼2350°C). [ABSTRACT FROM AUTHOR]

Continuous carbon fiber reinforced (SiC-ZrC) n multi-layer structural matrix composites were prepared by isothermal chemical vapor infiltration method. The microstructure, bending and ablation behavior of the composites with different number (n, n = 1, 2, 4) of SiC-ZrC layer were studied. The fracture morphology was step-like fracture. With the increase of n, the number of interfaces doubled, benefiting that the cracks kept deflecting and branching at the interface to consume lots of energy. The bending strength increased from 127.63 MPa (n = 1) to 276.85 MPa (n = 4). After ablation, among the prepared composites, C/(SiC-ZrC) 4 composite not only had the highest residual bending strength (169 MPa), but also had the best ablation resistance, which the mass and linear ablation rates were 1.17 ± 0.19 mg/s and 7.50 ± 0.56 µm/s, respectively. [ABSTRACT FROM AUTHOR]

In this study, Cu–Sn-based diamond composites were fabricated using L-PBF. The effects of the Cu-coated diamond on the melt-pool evolution, diamond–metal matrix bonding, thermal damage, and friction behavior of Cu in the Cu–Sn-based diamond composites were investigated. Moreover, the optimum L-PBF parameters for processing Cu-coated diamond/Cu–Sn composites were investigated. A convolutional neural network based on deep learning was used to process laser-scanned diamond images and evaluate the diamond thermal damage by model-feature visualization. The thermally damaged Cu-coated diamond and percentage of severely damaged parts were reduced compared to those of the uncoated diamond. Thick Cu coating changed the wettability of the diamond and matrix, thereby increasing the friction of the molten pool and unmelted metal particles and introducing the friction of the Cu microfluidic flow on the diamond. Hence, the mechanical holding force of the Cu Sn alloy matrix on the diamond substantially increased, and the bending strength of the Cu-coated diamond/Cu–Sn composites fabricated using L-PBF reached 720 MPa, which is approximately twice that of diamond/Cu–Sn (365 MPa). • Cu-coated diamond/Cu-Sn composite was formed by laser powder bed fusion. • The bending strength of Cu-coated diamond/Cu-Sn composites reached 720 MPa. • The thick Cu coatings improved the mechanical holding force on the diamond. • Laser-scanned-diamond prongs were susceptible to thermal damage. [ABSTRACT FROM AUTHOR]

To improve the reliability of C f /HfC-SiC composites after ablation, SiC fibers were used as reinforcement to replace carbon fibers. The composites were prepared by precursor infiltration and pyrolysis (PIP) and chemical vapor deposition (CVD) methods. The flexural properties of the cyclic ablated C f /HfC-SiC and SiC f /HfC-SiC composites were characterized. The results showed that the flexural strengths of C f /HfC-SiC and SiC f /HfC-SiC composites before ablation were 98.3 ± 6.8 and 108.5 ± 1.9 MPa, respectively. After three cycles of ablation, the flexural strengths of C f /HfC-SiC composites were 37.2 ± 2.4 MPa (decreased by about 62.2%), and the bending strengths of SiC f /HfC-SiC composites were 79.6 ± 4.3 MPa (only decreased by 26.6%). The high retention rate of the bending strength of SiC f /HfC-SiC composites was due to the protection of the complete oxide layer and good oxidation resistance of the SiC fiber. [ABSTRACT FROM AUTHOR]

• C f /HfC and C f @PyC/HfC composites were prepared at low temperature by precursor infiltration and pyrolysis and chemical vapor deposition method. • The results of thermal cyclic ablation and three-point bending tests show that after three time ablation cycles, the flexural strength of C f /HfC samples reduced by 63%; the flexural strength of C f @PyC/HfC samples only reduced by 36%. • The differences of cyclic ablation behaviour and flexural strength of C f /HfC and C f @PyC/HfC are attributed to the crucial function of PyC interface phase including protection of fiber and weakening of fiber/matrix interface. Composites based on hafnium carbide and reinforced with continuous naked carbon fiber with and without PyC interface were prepared at low temperature by precursor infiltration and pyrolysis and chemical vapor deposition method. The microstructure, mechanical property, cyclic ablation and fiber bundle push-in tests of the composites were investigated. The results show that after three times ablation cycles, the bending strength of samples without PyC interface decreased by 63.6 %; the bending strength of samples with PyC interface only decreased by 37.8 %. The force displacement curve of the samples with PyC interface presented a well pseudoplastic deformation state. The mechanical behavior difference of two kinds of composites was due to crucial function of PyC interface phase including protection of fiber and weakening of fiber/matrix interface. [ABSTRACT FROM AUTHOR]

In this study, selective laser melting (SLM), an additive manufacturing technology, is used to fabricate Co-Cr-Mo/diamond (10 vol%) composite samples for application in the field of diamond tools. To obtain suitable SLM processing parameters, the samples were optimized in terms of the three-dimensional roughness, microhardness, relative density, and bending strength. The results indicated that the optimal SLM processing parameters were a laser power of 220 W, scanning speed of 750 mm/s, and layer thickness of 0.05 mm, and the bending strength of the samples reached 1000 MPa. Furthermore, the influence of the laser energy on the melting of the mixed powder, expansion of the melt pool, and bonding of Co-Cr-Mo/diamond composites during the SLM process was determined simultaneously. In addition, the abrasion resistances of the Co-Cr-Mo and Co-Cr-Mo/diamond-composite samples were compared using frictional wear tests. The results showed that the mass-loss of the Co-Cr-Mo samples equalled 2.1%, and the friction coefficient increased continuously from 0.13 to 0.75 before stabilizing. The mass-loss of the Co-Cr-Mo/diamond-composite sample equalled 0.3%, and the coefficient of friction maintained a dynamic equilibrium of approximately 0.3, which indicated that the Co-Cr-Mo/diamond-composite sample had better abrasion resistance. This study provides a new method for fabricating complex diamond tools with a high concentration of diamond in a refractory metal matrix. • Co-Cr-Mo/diamond (10 vol%) composite was formed by selective laser melting. • Diamonds were firmly enfolded in the alloy matrix. • Diamonds were mitigated thermal damage due to the protecting of matrix. • Co-Cr-Mo/diamond composites had better frictional resistance. [ABSTRACT FROM AUTHOR]

• B-modified SiC/HfC-SiC composite has been fabricated by the combination of PIP and CVD. • The bending strength of cyclic ablated SiC/HfC-SiC and B-modified SiC/HfC-SiC composites have been characterized. • Effective residual thickness is proposed in this paper to present ablative dimensional stability. • After introducing boron, the effective residual thickness of ablated SiC/HfC-SiC composite increased significantly. The B-modified SiC/HfC-SiC composites were prepared by the combination of precursor infiltration and pyrolysis (PIP) and chemical vapor deposition (CVD) methods. The microstructure, cyclic ablation and bending strength tests of the SiC/HfC-SiC composites with and without B were investigated. The results showed that the B-modified composites had a better cyclic ablation resistance than that of the composites without B. The effective residual thickness of the B-modified composites was also higher than that of the composites without B after cyclic ablation. The residual bending strength of the B-modified composites was slightly lower than that of the composites without B. [ABSTRACT FROM AUTHOR]