TiB2 Content Research Articles

Effects of TiB2 content on the processability and mechanical performance of Hastelloy-X based composites fabricated by selective laser melting

Nickel-based Hastelloy X (HX) superalloy is susceptible to cracking when processed by selective laser melting (SLM) process. Previous studies have reported that the microcracks may be eliminated by adding 2 wt% TiB2 ceramic particles, while the modified HX materials are generally classified as HX-based composites. An investigation of the effects of different TiB2 contents (i.e. 1 wt% and 3 wt%) on SLM of HX-TiB2 composites would thus be interesting in terms of the processability, microstructure and mechanical performance. The results indicate that compared to pure HX, microcracks were not detected in the SLM-fabricated neither the HX- 1 wt% TiB2 (HX-1) nor the HX-3 wt% TiB2 (HX-3) composites due to the significant grain-refinement behaviour. The microcracks elimination together with the added TiB2 particles also contributed to a remarkable improvement in the composites’ tensile performance. The determined ultimate tensile strength of HX-1 and HX-3 were 77% and 106% higher than that of pure HX at 850 ℃, respectively. This research also explored the processability and microstructure of HX-TiB2 graded composites by combining the HX-1 and HX-3 via the SLM process, which offers a promising pathway to manufacture advanced components with graded structures and materials via the SLM process.

Influence of the TiB2 content on the processability, microstructure and high-temperature tensile performance of a Ni-based superalloy by laser powder bed fusion

The nickel-based GH3230 (Haynes 230) superalloy is widely used in the aerospace and power industries because of its excellent high-temperature strength and thermal stability. Owing to the crack susceptibility, however, GH3230 alloy offers poor processability processed by the laser powder bed fusion (LPBF) process. This paper systematically studies the processability, microstructure and high-temperature tensile performance of LPBF-fabricated GH3230 material modified by the addition of sub-micrometre TiB 2 particles. The results reveal that the addition of TiB 2 particles contributed to improving the processability of this alloy during the LPBF process. Also, the microcracking in LPBF-fabricated pure-GH3230 was addressed in the present study by introducing 1 wt% or 2 wt% sub-micrometre TiB 2 particles to GH3230 powder. When the addition of TiB 2 was up to 3 wt%, however, micro-cracks formed again. The micro-CT results confirmed that micro-cracks were the primary defects in the fabricated pure-GH3230 specimen, while only a limited number of open pores were detected in GH3230–1 wt% TiB 2 and GH3230–2 wt% TiB 2 specimens. The micro-cracks were categorised to solidification and solid-state cracking in terms of their formation mechanisms and characteristics. The yield-strength values of LPBF-fabricated GH3230–1 wt% TiB 2 and GH3230–2 wt% TiB 2 at 850 °C were examined to 254 MPa and 311 MPa, respectively, which were 29% and 59% higher than pure-GH3230. Compared to pure-GH3230, the elongation values of GH3230–1 wt% TiB 2 and GH3230–2 wt% TiB 2 were also significantly improved because of the elimination of micro-cracks. This work provides an effective route to eliminate cracks and to improve mechanical properties for Ni-based superalloys. • Microcracks categorised to solidification cracking and solid-state cracking. • Microcracking elimination achieved by introducing 1 wt% and 2 wt% TiB 2 . • The addition of 3 wt% TiB 2 enabled the formation of microcracks. • TiB 2 improved both laser absorption and thermal conductivity of the powder bed.

Microstructure and mechanical property of in-situ synthesized SiC–TiB2 porous ceramic as a function of TiB2 content

A convenient and promising one-step manufacturing processes was successfully developed to fabricate SiC–TiB2 porous ceramics. TiO2, B4C and sucrose were used as raw materials for in-situ generation of TiB2 phase, which promoted skeleton grain bonding and achieved highly interconnected pores simultaneously. The effect of different TiB2 volume fractions on porous structures, pore parameters, and mechanical properties was studied. SiC–TiB2 porous ceramics were obtained with porosities ranging from 36.2% to 41.9%, pore sizes ranging from 2 μm to 10 μm, and high compressive strength up to 169.5 MPa. Apart from the total porosity, TiB2 content, as well as pore/skeleton characteristics, were demonstrated as important factors affecting the mechanical properties. Hence, based on the strength-porosity relationship, an extended equation was proposed for modelling and optimizing the mechanical properties of biphasic porous ceramics.

The microstructure evolution and precipitation behavior of TiB2/Inconel 718 composites manufactured by selective laser melting

Additive Manufacturing is an advanced material processing technology emerging in recent years. However, coarse columnar grain structure of additive manufactured metals reduces the performance of the material. Facilitating the columnar to equiaxed transition (CET) has become a research hotspot. In this paper, the equiaxed grain of additive manufactured Inconel 718 was achieved by adding TiB2 particles. Simultaneously, the microstructure evolution and precipitation behavior with nano-TiB2 particles addition were studied. The results show that the grain morphology of Inconel 718 exhibited coarse columnar grains with epitaxial growth and strong <100> texture. When 3 wt% TiB2 was added, the columnar grains became finer, further increased the content of TiB2 to 5 wt%, the equiaxed grains were obtained and the texture intensity decreased significantly. In addition, TiB2 partially melted under the high laser energy changed the phase precipitation behavior of Inconel 718 from chain-like Laves phase to reticulated (γ + M3B2) eutectics, which lead to the hardness increased from 276 HV to 578 HV when 5 wt% TiB2 was added. After heat treatment, the precipitation of high density γ′ and γ″ strengthening phase were promoted the hardness increased by 87% to 516 HV in Inconel 718. However, the hardness of TiB2 reinforced samples showed a little change, which could be attributed to the partial dissolution of M3B2 boride during the heat treatment.

High‐strength TiB2‐B4C composite ceramics sintered by spark plasma sintering

AbstractSpark plasma sintering (SPS) is an advanced sintering technique because of its fast sintering speed and short dwelling time. In this study, TiB2, Y2O3, Al2O3, and different contents of B4C were used as the raw materials to synthesize TiB2‐B4C composites ceramics at 1850°C under a uniaxial loading of 48 MPa for 10 min via SPS in vacuum. The influence of different B4C content on the microstructure and mechanical properties of TiB2‐B4C composites ceramics are explored. The experimental results show that TiB2‐B4C composite ceramic achieves relatively good comprehensive properties and exceptionally excellent flexural strength when the addition amount of B4C reaches 10 wt.%. Its relative density, Vickers hardness, fracture toughness, and flexural strength reach to 99.20%, 24.65 ± .66 GPa, 3.16 MPa·m1/2, 730.65 ± 74.11 MPa, respectively.

Prediction of macroscopic effective elastic modulus of micro-nano-composite ceramic tool materials based on microstructure model

In order to investigate the effect of microstructure parameters on the elastic modulus, based on the microstructure model represented by Voronoi tessellation, the reasonable macro-micro connection and boundary conditions were proved through the Hill’s lemma, and the uniaxial tensile process of composite ceramic tool materials was simulated. The influences of grain size, second phase volume fraction and nanoparticle volume fraction on elastic properties were studied through numerical simulation, and the elastic modulus of composite ceramic tool materials was predicted. The results showed the elastic modulus of Al2O3-based ceramic tool materials could be increased effectively with the contents of the second phase TiB2 and nano-particle TiC being 20% and 10%, respectively. The numerical simulation results were in good agreement with the experimental results.

A nano-indentation study of hot consolidated steel matrix composite

Steel matrix composites (SMCs) are quite interesting materials for high temperature applications due to synergetic effect of hard ceramic particles and ductile matrix. In the present article, 304 stainless steel matrix composites with 2–4 vol% TiB2 particles were produced by hot pressing route. Deformation behaviour of the composites under constant load was evaluated by conducting nanoindentation tests. Microstructural analysis revealed uniform distribution of particles in the matrix. Based on the load- penetration depth curve results, reduction in depth of around 12–28% was observed in 2 vol% and 4 vol% composites respectively compared to unreinforced steel. Use of TiB2 as reinforcement was found to be beneficial for improvement of strength and hardness as compared to their unreinforced counterpart. Composite with 4 vol% TiB2 resulted in highest strength and hardness owing to load carrying capacity of stiff reinforcement from the matrix. The plastic recovery of the composites was found to be decreased with increase in TiB2 content according to the calculation of plastic energy dissipation based on the nanoindentation results. It is expected that the observed results can provide a powerful platform for the design and production of steel based composites with desired mechanical properties.

Mechanical properties of casting titanium alloy matrix composites reinforced by WC and TiB2 ceramic particulates

Casting Titanium alloys with Wc and TiB2 additives have their mechanical characteristics examined in this work. The mechanical properties of aged titanium alloys are very impressive. UTS reach 406 MPa and YS of 253 MPa and an El of 7.4 percent. Pinned primary Wc and TiB2 phases reduced fineness by more than half, while enhancing assorted nucleation on Wc and TiB2 initial phases boosted nucleation and growth resistance. Following the heat treatment, foundational designed with the intent emerged from the substrate. There are no more stages in the shell. Those alloys containing Wc, on the other hand, have cores composed of Wc and TiB2. From 0.1 wt% to 0.2 wt% of Wc and TiB2 content, core radius rises, but shell width does not appear to change, and particle density does not appear to be altered. In time, composite particles became coarser, but their core dimensions stayed nearly same. As predicted, the exponent (n-1) is less than the expected value of 0.33, Perhaps this is because of the low temperature, which prevents a developed a semi state from emerging. The kinetics are consistent with the KV model's predictions.

Experimental investigations on properties of MoS2 and TiB2 reinforced aluminium composites

In this work, Aluminum Alloy (AA 6081) matrix composites reinforced with Molybdenum disulfide (MoS2) and Titanium Diboride (TiB2) have been developed through stir casting (SC) method. Influence of TiB2 on the properties of the aluminium composite was studied. The incorporation of TiB2 in the AA6081-2MoS2 matrix improved hardness of the composite. The improved tensile strength (TS) and compressive strength (CS) was obtained for the AA6081-2MoS2-12 wt% TiB2 composite. The high impact strength (IS) is obtained for the AA6081-2MoS2-8 wt% TiB2 composite. The decreased elongation was observed for the increasing content of TiB2. The high bending strength (BS) was obtained for the AA6081-2MoS2-8 wt% TiB2 composite.

STUDY ON THE DENSIFICATION OF ALN-TIB2 COMPOSITES BY HOT PRESSED SINTERING

The AlN-TiB2 composites were prepared by hot pressing sintering process and the effects of TiB2 content and sintering process on the densification of AlN-TiB2 composites were studied. The results showed that at 1900℃ for 1h, the relative density reached more than 98.6% and the TiB2 content had no effect on densification of the composites. The phase composition and microstructure of the composites were also studied. Two-phase BN and TiN are newly formed in the sintering process of AlN-TiB2 multiphase material, so the multiphase material is composed of four phases, the primary crystal phase is AlN and TiB2, and the secondary crystal phase is BN and TiN. With the increase of sintering temperature and the extension of holding time, the density of AlN-TiB2 multiphase materials gradually increases. The optimum sintering temperature and holding time were 1900℃ and 1h respectively. The addition of TiB2 does not affect the sintering of multiphase materials.The multiphase materials have achieved high density.

Effect of TiB2 Content on Properties of Nickel-Coated Graphite Self-Lubricating Coating Prepared by Laser Cladding

To improve the anti-wear and friction-reducing properties of self-lubricating coatings, Ni60/Nickel-coated graphite/TiB2 composite coatings with different contents were prepared by laser cladding. The coating properties were characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM), energy spectrometer (EDS), electrochemical workstation, micro-Vickers hardness tester, and friction and wear tester. The results showed that with the increase in TiB2 content, the graphite morphology changed from spherical at 0 wt.% TiB2 content to a little black graphite alone at 14 wt.% TiB2 to irregular agglomerates at 22 wt.% TiB2. Furthermore, the hardness of the coatings increased with increasing TiB2 content, and the 63% Ni60 + 15% nickel-coated graphite + 22% TiB2 coating had the highest hardness. TiC and Cr7C3 were generated in the coatings with the addition of nickel-coated graphite, creating a dispersion reinforcement effect, so that the hardness of these coatings was higher than that of the 86% Ni60 + 0% nickel-coated graphite + 14% TiB2 coating without the addition of nickel-coated graphite. In addition, the 71% Ni60 + 15% Ni-coated graphite + 14% TiB2 coating had the lowest friction coefficient, wear loss, and wear volume, thus exhibiting excellent friction reduction and anti-wear properties. The 71% Ni60 + 15% nickel-coated graphite + 14% TiB2 coating had excellent corrosion resistance.

Development of spark plasma sintered conductive SiC–TiB2 composites for electrical discharge machining applications

AbstractHighly dense electrically conductive silicon carbide (SiC)–(0, 10, 20, and 30 vol%) titanium boride (TiB2) composites with 10 vol% of Y2O3–AlN additives were fabricated at a relatively low temperature of 1800°C by spark plasma sintering in nitrogen atmosphere. Phase analysis of sintered composites reveals suppressed β→α phase transformation due to low sintering temperature, nitride additives, and nitrogen sintering atmosphere. With increase in TiB2 content, hardness increased from 20.6 to 23.7 GPa and fracture toughness increased from 3.6 to 5.5 MPa m1/2. The electrical conductivity increased to a remarkable 2.72 × 103 (Ω cm)–1 for SiC–30 vol% TiB2 composites due to large amount of conductive reinforcement, additive composition, and sintering in nitrogen atmosphere. The successful electrical discharge machining illustrates potential of the sintered SiC–TiB2 composites toward extending the application regime of conventional SiC‐based ceramics.

Phase-field modeling of grain evolution in additive manufacturing with addition of reinforcing particles

Metal matrix composite parts fabricated by additive manufacturing are of interest due to their fine grain structures and superior mechanical properties. In this study, a phase-field (PF) model is developed to simulate the grain evolution of TiB 2 /316L stainless steel composite during the selective laser melting (SLM) process. The reinforcing TiB 2 particles are explicitly incorporated into the PF model, and the influences on grain evolutions are comprehensively considered, including the induced heterogeneous nucleation and the pinning effect on grain boundaries. The simulation results demonstrate that with the addition of TiB 2 particles, both columnar and equiaxed grains are formed in the scanning track. While the columnar grains are due to epitaxial growth from the molten pool boundary, the TiB 2 particles act as the nucleation sites inside the molten pool, resulting in the formation of equiaxed grains. The grain boundaries become complicated due to the pinning of grain boundaries by TiB 2 particles. As the content of TiB 2 particles increases, the grain size decreases and the equiaxed grains are closer to the fusion boundary of the scanning track, which are attributed to the increasing nucleation sites and the retarded grain growth during solidification. In addition, the grain coarsening in previous layers is restrained due to the Zener pinning effect. The simulated grain morphology and the predicted influence trend of the TiB 2 content on grain morphology are in good agreement with the experimental observations in the literature.

Mechanical Properties of Hot-Pressed B&lt;sub&gt;4&lt;/sub&gt;C-TiB&lt;sub&gt;2&lt;/sub&gt; Composites Synthesized from B&lt;sub&gt;4&lt;/sub&gt;C-TiO&lt;sub&gt;2&lt;/sub&gt; and B&lt;sub&gt;4&lt;/sub&gt;C-TiC

In this study, B4C-TiB2 ceramic composites were manufactured by hot pressing method. The raw materials for the in-situ synthesis of TiB2 were TiO2 and TiC. After being sintered at 1900°C for 60min under a pressure of 30MPa, compact composites samples with a TiB2 volume fraction range from 0 to 11.05% were prepared. The relative density, fracture toughness and flexural strength of different sample were tested. Microstructures on the fracture surface were studied by SEM. The result shows that B4C-TiB2 ceramic composites sintered from B4C-TiC had a better mechanical property than the one sintered from B4C-TiO2. When the content of TiB2 (reacted from TiC) was 11.05vol.%, the strength and toughness of B4C-TiB2 ceramics can reach 598MPa and 6.45MPa·m1/2. The toughening mechanisms of B4C-TiB2 composites include micro-crack toughening and energy consumption by the pulling out process of second phase.

Enhanced Antiwear Property of Cu-Sn-Bi Bimetal Composites with TiB2 under Different Working Conditions

The present study investigated the effect of TiB2 on the tribological properties of CuSn10Bi3 bimetallic bearing materials. CuSn10Bi3 samples with different contents of TiB2 were fabricated by powder sintering technology. Their metallographic structures and tribological characteristics under different working conditions were analyzed and compared. The results showed that TiB2 refine the copper alloy grains, passivate the grain boundary edges and reduce the surface porosity of the sample. When the content of TiB2 is 1%, the wear rate under different oil conditions (oil-rich, oilless, and dry friction) is reduced by 42%-95%. The sharp decrease in the wear rate is attributed to the enhancement of the micro-grain structure of the copper alloy matrix material by TiB2 hard particles with antiwear properties, and the high hardness and high wear resistance of TiB2. The wear tracks were analyzed through SEM and EDS, and it was concluded that the addition of TiB2 enhanced the wear resistance.

Microstructure and mechanical properties of B4C–TiB2 ceramic composites prepared via a two-step method

B4C–TiB2 ceramic composites were fabricated by a two-step method. First, B4C–TiB2 composite powders were synthesized from TiC–B powder mixtures at 1400 ℃, then mixed with commercial B4C powders by ball milling and the B4C–TiB2 ceramic composites were prepared by hot pressing at 1950 ℃. This two-step method not only effectively refined TiB2 grains, but also allowed the composition of the composites to be freely designed. The microstructure and mechanical properties of the composites were investigated. The results showed that the B4C–TiB2 ceramic composite with a 10 wt% TiB2 content obtained the ideal comprehensive performance, with a volume density, Vickers hardness, bending strength, and fracture toughness of 2.61 g/cm3, 35.3 GPa, 708 MPa, and 5.82 MPa m1/2, respectively. The advantages of the in-situ reaction process were fully exerted by the two-step method, which made a remarkable contribution to the excellent properties of B4C–TiB2 ceramic composites.

High-Temperature Tribological Behaviors of In Situ–Formed TiAl-TiB2 Composites in Low-Pressure Oxygen

The tribological behaviors of in situ–formed TiAl-TiB2 composites were investigated from room temperature to 800 °C in low-pressure oxygen and related to their hardness and partial tribo-oxidation behaviors on the frictional surface. The wear resistance of TiAl-TiB2 composites in low-pressure oxygen is significantly enhanced when the TiB2 content increases from 0 to 20 vol% but decreases with a further increase in TiB2 content to 30 and 40 vol%. The wear rates of the TiAl-TiB2 composites are low below 200 °C and increase within 400–600 °C due to their decreased hardness and reach minimum values at 800 °C. The hardness of the composites and the degree of surface tribo-oxidation codetermine the wear resistance.

Effect of TiB2 content on microstructure and mechanical properties of (TiB2p+B4Cp)/Al composites fabricated by microwave sintering

Abstract This study demonstrates a novel method to improve the density, interface bonding strength and mechanical properties of the B4Cp/Al composites by directly adding TiB2 to the material. Specifically, the (TiB2p+B4Cp)/Al composites with different TiB2 contents were successfully fabricated by ball milling (BM) and microwave sintering (MS). The results indicate that the developed (TiB2p+B4Cp)/Al possess a clean interface, with the absence of any reaction, thus, confirming microwave sintering as one of the preferred ways to prepare the (TiB2p+B4Cp)/Al composites. On adding TiB2, the densification in the microstructure is noted to initially increase, followed by a decrease. Overall, the TiB2 and B4C particles are noted to synergistically improve the densification as well as ameliorate the interfaces and microstructure. As a result, the optimized composites exhibit the compactness and Vickers hardness as high as 94.6% and 153.42HV0.3 respectively. The highest value of the compressive strength is determined to be 578.71 MPa at 50.0%. Further, no macroscopic fracture is noted to occur after 50% compression strain.

Mechanical Properties and Microstructures of Al2O3/TiC/TiB2 Ceramic Tool Material

In order to develop a new ceramic tool material with self-repairing capability, Al2O3/TiC/TiB2 ceramic tool material was prepared by vacuum hot-pressure sintering method. The toughening and strengthening mechanism of TiB2 on Al2O3/TiC substrate was analyzed. The results show that the ceramic tool material has good comprehensive mechanical properties when the TiB2 content is 10 vol.%. Its flexural strength was 701.32 MPa, hardness was 18.3 GPa, and fracture toughness was 6.2 MPa·m1/2, which were improved by 11.6%, 2.2% and 16.1% respectively, compared with the Al2O3/TiC tool material. Fracture surfaces of the Al2O3/TiC/TiB2 ceramic tool material were characterized by SEM, EDS and XRD. The results showed that the fracture mode was a mixture of transgranular fracture and intergranular fracture. The growth of Al2O3 and TiC grains can be effectively inhibited by adding appropriate amount of TiB2, and the internal grains of the material can be refined. The TiB2 has a uniform distribution in the matrix and acts as a diffusion toughening agent. The cutting performance of Al2O3/TiC/10 vol.%TiB2 tool material was further investigated. Experiments conducted on tools made of Al2O3/TiC and Al2O3/TiC/TiB2 materials showed that the main forms of wear for both tools were abrasive wear and bonded wear. The friction coefficient of Al2O3/TiC/TiB2 tools was reduced by 10.77% compared to Al2O3/TiC tools.

Special Issue on Tribology of Additive Manufacturing

Special Issue on Tribology of Additive Manufacturing