► TiC–TiB2 composites coatings were produced on Mg alloy by reactive plasma spraying. ► Phase composition, microstructure and wear resistance of the coatings were studied. ► The resultant product in ...the coatings was composed of TiC and TiB2. ► The produced coatings displayed porous and dense microstructures. ► The synthesized coatings exhibited good wear resistance for Mg alloy substrate.
TiC–TiB2 composite coatings were successfully synthesized using the technique of reactive plasma spraying (RPS) on a magnesium alloy. Phase composition, microstructure and wear resistance of the coatings were characterized by using X-ray diffraction, scanning electron microscopy and pin-on-disk wear test, respectively. The results showed that the resultant product in the RPS coatings was composed of TiC and TiB2. Depending on the ignition of self-propagating high-temperature synthesis reaction in the agglomerate particles, the RPS coatings displayed porous and dense microstructures. The porosity of the RPS coatings, to some extent, decreased when the feed powders were plasma sprayed with Ni powders. The RPS coatings provided good wear resistance for the substrate under various loads. For high loads (e.g., ≥15N), the wear resistance could be significantly improved by the proper addition of Ni into the RPS coatings.
TiC–TiB2–NiAl composites were fabricated by self-propagating high temperature reaction synthesis(SHS) with Ti, B4C, Ni and Al powders as raw materials. The effects of NiAl content on phase ...constituents and microstructures were investigated. The results show that the reaction products are composed of TiB2, TiC and NiAl. The content of NiAl increases with the adding of Ni+Al in green compacts. TiB2, TiC and NiAl grains present in different shapes in the matrix, TiB2 being in hexagonal or rectangular shapes, TiC in spherical shapes, and NiAl squeezed into the gaps of TiC and TiB2 grains. With the increase of NiAl content, the grains of TiC–TiB2–NiAl composites are refined, their density and compressive strength are improved, and the shapes of TiC grains become spherical instead of irregular ones. Finally, the fracture mechanism of the composites transforms from intergranular fracture mode to the compounded fracture mode of intergranular fracture and transgranular fracture.
•The synthesis of (TiC–TiB2)–Ni and bonding to Ti were simultaneously accomplished.•Higher pressure led to smaller TiC and TiB2 particles.•Shear experiments showed that fracture occurred on ...(TiC–TiB2)–Ni and TiAl interface.•The lubrication films formed at elevated temperature resulted in a smaller mass loss.
The composite ceramics TiC–TiB2 with Ni as the binder were successfully fabricated and bonded with Ti using TiAl as the transitional layer. (TiC–TiB2)–Ni composite ceramics were prepared in-situ through the combustion synthesis process using titanium, nickel and B4C powders as raw materials. Interfacial investigations of (TiC–TiB2)–Ni/TiAl and TiAl/Ti showed that the three layers were bonded together very well. The TiC and TiB2 particles of the synthesized composite ceramics were fine and homogeneously dispersed in the matrix. The shear strength increased as the applied current and pressure increased, with the maximum shear strength of the joint reaching 85.78MPa. The fracture morphology investigated by SEM indicated that the fracture occurred in the (TiC–TiB2)–Ni/TiAl interface. The friction coefficient and the loss rate of the ceramic (TiC–TiB2)–Ni decreased as the testing temperature increased. The lubrication films of Fe2O3, TiO2, and B2O3 formed at an elevated temperature resulted in a smaller mass loss and friction coefficient.
By applying combustion synthesis in high-gravity field, the TiC–TiB2 ceramic composites were prepared under different gravitational conditions from 500g to 2500g. XRD, FESEM and EDS results showed ...that there is no significant change in phase composition of TiC–TiB2, but a remarkable decrease of Al2O3 inclusions with the high-gravity field increased. Meanwhile, the well-developed faceted TiB2 grains with narrow size distribution were observed. Therefore, it can be proposed that the ultra-high-gravity field not only enhances the Al2O3 liquid separation from TiC–TiB2 liquid during the combustion synthesis process, but also promotes the microstructure refinement of the reaction products. The results of the mechanical test showed that the mechanical performance of TiC–TiB2 ceramic can be improved by increasing high-gravity field, especially its relative density, fracture toughness and bending strength.
•The combustion synthesis of TiC–TiB2 ceramics in high gravity field is introduced.•The refractoryTiC–TiB2 ceramic with high hardness are prepared by solidification.•The effects of ultra-high-gravity field on TiC–TiB2 Ceramics are discussed.•The correlations of the microstructures and properties are discussed.
The effect of B4C particle size on the reaction behavior of TiC–TiB2 ceramic/Cu composites from a 40wt.% Cu–Ti–B4C system by self-propagation high-temperature synthesis (SHS) was investigated. It was ...found that increasing B4C particle size not only makes the ignition and self-sustainment of the SHS reaction difficult but also decreases the combustion temperature and combustion wave velocity. The reaction products are dependent on the B4C particle size. Favorable composites consisting of TiC, TiB2 and Cu phases could be obtained by the control of B4C particle size. The reaction path was explored through a delicate microstructure and phase analysis on the combustion-wave quenching method. From the reaction path, the effect of B4C particle size on the ignition behavior, combustion characteristics and products of the Cu–Ti–B4C system can be clearly clarified.
•The reaction behavior was dependent on the B4C particle size.•The reaction path was explored using combustion-wave quenching method.•Diffusion rate of carbon and boron plays an important role.
A series of solidified TiC–TiB2 were fabricated by combustion synthesis integrated with ultra high gravity, and the ceramics were comprised of TiB2 primary phases, irregular TiC secondary phases, a ...few of Al2O3 inclusions and Cr-based metallic phases. Obviously, the increased high gravity field promoted phase separation of Al2O3 droplets from the molten reaction products, which resulted in not only the rapidly reduced Al2O3 inclusions but also the refined microstructure and the improved homogeneity. When high gravity acceleration reached 2500g, the ultrafine-grained microstructure with the average thickness of TiB2 platelets smaller than 1 μm was achieved. More and more fine TiB2 platelets with aspect ratio of 4–6 participated in the toughening mechanism of crack bridging and subsequent pullout, the maximum fracture toughness could amount to 16.5±1.0MPam0.5. Because of rapidly reduced Al2O3 inclusions, the refined microstructure and the improved homogeneity were obtained in the near full-density composite, the maximum flexural strength of 982±20MPa was also simultaneously achieved in the solidified TiC–TiB2 composite at 2500g.
TiC-TiB2 composite ceramics were successfully fabricated via planetary ball milling of 72 mass% Ti and 28 mass % B4C powders, followed by low temperature sintering process at 1200°C. The ...microstructure of the ball-milled powder mixtures and composite ceramics were characterized by Differential thermal analysis equipment (DTA), field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). The results showed that the ball-milled powder mixtures (Ti and B4C powders) were completely transformed to TiC-TiB2 composite ceramics as the powders were milled for 60 h and sintered at 1200°C for 1 h. The formation mechanism of the TiC-TiB2 composite was discussed. The high energy ball milling and necessary sintering for the powder mixtures plays an important role in the formation of the composites.
TiC-TiB2/Cu composites were prepared by self-propagating high-temperature synthesis with pseudo hot isostatic pressing using Ti, B4C, and Cu powders. The compressive deformation of the composites at ...high tem- perature was investigated. It is found that the maximum compressive strength decreases with the increase of tem- perature and Cu content. The deformation of the composites includes the steps of elastic, stable theology, and inaction. The maximum strain is in the range of 5 %-10 %. Before fracture, TiC-TiB2/40Cu becomes drum-shaped at 1123 K; however, TiC-TiB2/20Cu only has a brittle frac- ture along the axial direction of 45~. The results show that the compressive strength of TiC-TiB2/Cu decreases from 823 to 1223 K. However, the maximum compressive strength of TiC-TiB2/20Cu reaches 1850 MPa at 823 K, which predicts that this series of composites could be applied to high-temperature compressive materials.
The （TiC-TiB2）/Cu composites with 50 vol% TiC-TiB2 ceramic particles were successfully fabricated by the combustion synthesis and hot press consolidation in a Cu-Ti-B4C-Cr system. The effects of the ...Cr content on the microstructures, hardness, compression properties, and abrasive wear behaviors of the composites were investigated. The final products consist of only Cu, TiC, and TiB2 phases, and the ceramic particles are distributed uniformly in these composites. The size of the ceramic particles decreases with Cr addition. As the Cr content increases, the yield strength, ultimate compression strength, microhardness, and abrasive wear resistance of the composites increase, and the fracture strain decreases.
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