Carbonitride Composites Research Articles

Densification and corrosion properties of graphite reinforced binderless TiC70N30 ceramic composites

In this study, binderless TiC70N30 ceramic composites with varying graphite (TiC70N30–Gr) reinforcements were fabricated via spark plasma sintering and their effect on densification was assessed. Subsequently, the electrochemical behaviour of TiC70N30–Gr composites was evaluated in 0.5 mol/L hydrochloric acid (HCl), 0.5 mol/L sulphuric acid (H2SO4) and 0.5 mol/L nitric acid (HNO3) solutions using open circuit potential, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods. The corrosion behaviour of TiC70N30-based ceramic composites with and without graphite reinforcement exhibited high corrosion resistance in the acidic electrolytes. Composites with 0.5 and 1.0 wt% graphite content showed lower Icorr values of 0.452 µA and 0.081 µA in 0.5 mol/L HCL and 0.5 mol/L HNO3, respectively, while specimen without graphite addition showed better corrosion resistance in 0.5 mol/L H2SO4 (0.041 µA). Based on the corrosion results, the corrosion properties of TiC70N30 ceramic composites in HCl and HNO3 solutions were significantly enhanced upon the incorporation of graphite reinforcements. However, the corrosion test results conducted in H2SO4 solution showed that the addition of graphite had a negligible influence on the corrosion resistance of the titanium carbonitride (TiCN) composites.

Decomposition behavior and evolution mechanism of MC primary carbonitride at 1473K and 1523K in die steel

Evolution of morphology and chemical composition and decomposition behavior of MC-type primary carbonitride held at 1473K and 1523K in H13 die steel are studied through electron probe microanalyzer (EPMA) and optical microscope (OM). Result shows that the decomposition of MC-type carbonitride has a relationship with constituent, holding temperature and time and carbonitride structure. It is found that Fe would diffuse to carbonitride from steel matrix accompanied by the decomposition of carbonitride at elevated temperature. The metastable (Vx,Mo1–x)(Cy,N1–y) is transformed into fine Fe-rich (Vx,Moz,Fe1–x–z)6(Cy,N1–y) when held at 1473K, and completely disappeared when held at 1523K. During isothermal holding, the mean size of carbonitride is gradually decreased to 6.5 μm, but there are still a small quantity of (Tix,V1–x)(Cy,N1–y) when held at 1253K for 15 h. Theoretical calculation indicates that Ti content in carbonitride is directly proportional to the thermal stability of carbonitride. As a result, the (Tix,V1–x)(Cy,N1–y) is transformed into (Tix,Vz,Fe1–x–z)(Cy,N1–y) with Fe content larger than 13 wt.% and becomes jagged at the edge. The compact (Tix,V1–x)(Cy,N1–y) is then evolved into the porous fishnet structure and finally dissolved as Fe larger than 32 wt.% in carbonitride. High temperature seems more beneficial for carbonitride decomposition than extension of holding time.

Effect of N2- and CO2-containing shielding gases on composition modification and carbonitride precipitation in wire arc additive manufactured grade 91 steel

Additive manufacturing (AM) represents a promising technique to fabricate metallic alloys with greater control of the resulting material features as compared to traditional manufacturing routes. Recently, there is greater interest in AM research on 9 wt% Cr ferritic/martensitic (F/M) steels, which are commonly studied for use in the nuclear energy industry. This research aims to prove that wire arc AM can manufacture F/M steels with adequate mechanical properties in multiple processing atmospheres and aims to study how shielding gas composition can be leveraged during fabrication to induce specific precipitation pathways. The effect of shielding gas composition on MX (M=Nb and/or V, XC and/or N) carbonitride precipitation in a 9 wt% Cr ferritic/martensitic (F/M) steel alloy known as Grade 91 was studied using N2 and CO2 gas additions to an inert Ar shielding gas atmosphere during wire arc AM. The N and C atoms present in the processing atmospheres were absorbed into the melt pools during fabrication. Due to their differing affinities for precipitate-forming reactions, the varying levels of C and N between the samples contributed to differences in final carbonitride composition and morphologies. Such precipitate behavior is of interest as carbonitrides have been shown to contribute to increased mechanical performance. This increased performance was studied via electron microscopy and tested for strength, ductility, and fracture properties.

Mechanical and thermal shock properties of Cf/SiBCN composite: Effect of sintering densification and fiber coating

AbstractIn this work, resin‐derived carbon coating was prepared on carbon fibers by polymer impregnation pyrolysis method, then silicoboron carbonitride powder was prepared by mechanical alloying, and finally carbon fiber‐reinforced silicoboron carbonitride composites were prepared by hot‐pressing process. The effects of sintering densification and fiber coating on microstructure, mechanical properties, thermal shock resistance, and failure mechanisms of the composites were studied. Fiber bridging hinders the sintering densification, causing more defects in fiber‐dense area and lower strength. However, higher sintering temperature (1800–2000°C) can improve mechanical properties significantly, including bending strength, vickers hardness, and elastic module, because further sintering densification enhances matrix strength and fiber/matrix bonding strength, while the change of fracture toughness is not obvious (2.24–2.38 MPa·m1/2) due to counteraction of higher debonding resistance and less pull‐out length. However, fiber coating improves fracture toughness greatly via protecting carbon fibers from chemical corrosion and damage of thermal stress and external stress. Due to lower coefficient of thermal expansion, lower fiber loading ratio, less stress concentration at the fiber/matrix interface, and better defect healing effect, lower sintering temperature favors thermal shock resistance of composites, and thermal shock recession mechanisms are the damage of interface.

High-Performance Room-Light-Driven β-AgVO3/mpg-C3N4 Core/Shell Photocatalyst Prepared by Mechanochemical Method

A new highly efficient, visible light active, silver vanadate/polymeric carbonitride “core/shell” photocatalyst was prepared mechano-chemically prepared by grinding mixtures of β-silver vanadate and mesoporous graphitic carbonitride. Besides the core/shell photocatalyst, β-silver vanadate/mesoporous polymeric carbonitride composites and supported mpg-C3N4@β-silver vanadates were prepared. The materials were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), nitrogen ad- and de-sorption, diffuse reflectance UV-Vis measurement (DRS), infrared spectroscopy, Raman microscopy, and time-resolved photoluminescence spectroscopy. The photocatalytic performance of the materials was investigated in the degradation of organics using pharmaceutical ibuprofen and 4-(isobutyl phenyl) propionic acid sodium salt as model compounds under batch conditions. Reaction intermediates were studied by electrospray ionization and time-of-flight mass spectrometry (ESI-TOF-MS). Additionally, the degree of mineralization was determined by total organic carbon TOC measurements. The core/shell photocatalyst has shown superior photocatalytic activity compared to the other prepared composites or supported photocatalysts as well as the single mpg-C3N4. Scavenger experiments showed that valence band holes and anionic superoxide radicals are the main active species in the photocatalytic process. TOC measurement confirmed the mineralization of the organic compound, which was in line with ESI-TOF-MS experiments. Time-resolved photoluminescence measurements indicated that charges generated in carbonitride migrate via diffusive hopping and exhibit increased mobility in the case of the silver vanadate/polymeric carbonitride composite.

Wear-Resistant TiCN-Based Ceramic Materials for High-Load Friction Units

The tribological properties of matrix and skeletal titanium carbonitride composites were studied in dry friction conditions in air. Experiments on wetting of the TiCN–Cr3C2 composite by nickel–chromium alloys and copper using the sessile drop method were performed to choose matrix composition and ascertain whether the samples could be produced by impregnation of the porous skeleton. The sessile drop experiments showed that nickel and its alloys formed a low contact angle on the TiCN–Cr3C2 composite (θ ≈ 8°). In particular, Ni3Al intermetallic had θ < 5°, allowing it to be used as a metal matrix. The same situation was observed for copper. A technique was developed for producing TiN–Cr3C2 composites by impregnation of the porous skeleton with Ni3Al and copper melts, and the tribological behavior of the cermets was tested in dry friction conditions. When the starting composite was impregnated with Ni3Al intermetallic, the friction coefficient decreased (μ = = 0.25). Structural studies were conducted with a MIM-10 metallographic microscope and X-ray diffraction with a DRON-2 diffractometer. The hardness and contact area thickness were measured employing a Falcon 9 hardness tester (manufactured in the Netherlands). Thin cross sections were made to examine the structure and phase composition of the contact area. The structure was analyzed using X-ray diffraction and scanning electron microscopy. The effect exerted by hardness of the counterface (steel 45, 40Kh, ShKh15) on the tribological properties of the TiCN–Cr3C2 composite was established. When steel hardness was 60 HRC, the friction coefficient increased with friction distance. These results were, however, obtained at low speeds and loads. Friction losses decreased with loading increasing from 2 to 6 MPa at 12 m/sec: friction coefficient reduced to 0.23. The TiCN–20% Cr3C2 cermets impregnated with Ni3Al may be recommended as antifriction materials for use in high-speed and high-load friction units.

Strong and thermostable hydrothermal carbon coated 3D needled carbon fiber reinforced silicon-boron carbonitride composites with broadband and tunable high-performance microwave absorption

Excellent electromagnetic wave (EMW) absorbing materials with high-temperature stable and superior mechanical properties are among the most promising candidates for practical application. Here, novel hydrothermal carbon coated three-dimensional (3D) needled carbon fiber reinforced silicon-boron carbonitride (HC-CF/SiBCN) composites with a hierarchical A (CF)/B (HC)/C (SiBCN) structure were constructed and prepared for the first time by combining hydrothermal transformation and precursor infiltration and pyrolysis (PIP) process. The thickness of the HC coating controlled by the glucose concentration played a crucial role in tailoring the EMW capacity of the composite. The incorporation of SiBCN could not only effectively improve the oxidation resistance but also actively enhance the mechanical properties of the HC coated CF structure. Compared to the weak high-temperature oxidation resistance and mechanical properties of pristine 3D needled CF felt, the composites after the introduction of HC and SiBCN were thermostable in air atmosphere beyond 1000 °C to about above 70% weight retention, and the maximum flexural and compression strength of the composites could reach to 23.51 ± 1.37 and 12.22 ± 1.12 MPa, respectively. A substantial enhancement of EMW absorption ability was achieved through incorporation of HC and SiBCN, which could be attributed to the matched characteristic impedance and enhanced loss ability, whose optimization EMW absorption performance was the minimum reflection loss (RLmin) of −52.08 dB and effective absorption bandwidth (EAB) of 7.64 GHz for the composite obtained by two PIP cycles with 24 wt% glucose solution, demonstrating that the HC-CF/SiBCN composites with high-temperature stable, excellent mechanical and superior EMW absorption properties could be considered as a promising candidate for the applications in harsh environments.

Regularities of Metallurgical Reactions of Ti1 –n $${\text{Me}}_{n}^{{\text{V}}}$$ C0.5N0.5 Carbonitrides with the Ni–Mo Melt

The influence of alloying TiC0.5N0.5 carbonitride by transition metals of Group V (V, Nb, and Ta) on the contact interaction mechanism with the Ni–25%Mo melt (T = 1450°C, τ = 1 h, rarefaction is 5 × 10–2 Pa) is systematically studied by X-ray spectral microanalysis and scanning electron microscopy for the first time. It is established that the dissolution of single-type Ti1 –n $${\text{Me}}_{n}^{{\text{V}}}$$ C0.5N0.5 carbonitrides (n = 0.05) is an incongruent process (alloying metal and carbon preferentially transfer into the melt), and the relative rate and degree of incongruence of the dissolution process of carbonitrides in a series of alloying metals V–Nb–Ta vary nonmonotonically. An explanation for the discovered effects is proposed. The causal-effect relation between the initial composition of Ti0.95 $${\text{Me}}_{{0.05}}^{{\text{V}}}$$ C0.5N0.5 carbonitride (the grade of the alloying metal) and composition of the Ti1 – n – mMon $${\text{Me}}_{m}^{{\text{V}}}$$ Cx K-phase that is precipitated from the melt upon system cooling is analyzed. It is shown that the factor determining the composition of the forming K-phase is the ΔT factor (the degree of exceeding crystallization temperatures of carbide eutectics Ni/MeVC over the crystallization temperature of the Ni/Mo2C eutectic that is the lowest melting in these systems). The conclusion is argued that the interrelation between the initial carbonitride composition and the composition of the K-phase is a consequence of a microinhomogeneous structure of metallic alloys. It is shown that this interrelation is rather common and manifests itself in all studied systems irrespective of the type of alloying Group V metal and presence or absence of molybdenum in the melt.

Lithium intercalation into disordered carbon/SiCN composite. Part 2: Raman spectroscopy and 7Li MAS NMR investigation of lithium storage sites

Within this work, we analyze the lithium storage sites within carbon/silicon carbonitride (SiCN) composites. Commercial carbons, HD3 (hard carbon) and LD1N and LD2N (soft carbons), of varying porosity are impregnated with polysilazane (HTT 1800) and pyrolysed at 1100 °C. It is found in the first part of this study (Graczyk-Zajac et al. J Solid State Electrochem 19:2763–2769, 2015) that the initial porosity of the carbon phase plays an important role in determining the lithium insertion capacity and rate capability of the composite material. By applying Raman spectroscopy and solid-state 7Li MAS NMR on pristine, lithiated, and delithiated samples, we investigate the lithium storage sites within the composite materials. By means of Raman spectroscopy, it has been found that lithium storage in hard carbon-derived composites occurs in a significant extent via adsorption-like process within unorganized carbon, whereas for the soft carbon composites, storage in turbostratic carbon is identified. 7Li solid-state NMR confirms these findings revealing that more than 33 % of lithium stored in HD3/SiCN is adsorbed in ionic form at the surface and in pores of the composite, while around 38 % is stored between carbon layers. LD1N and LD2N composites store more than 50 % of lithium in the intercalation-type sites.

Precipitation Behaviour of Carbonitrides in Ti-Nb-C-N Microalloyed Steels and an Engineering Application with Homogenously Precipitated Nano-particles

A thermodynamic model enabling calculation of equilibrium carbonitride composition and relative amounts as a function of steel composition and temperature has been developed previously based on the chemical equilibrium method. In the present work, actual carbonitride precipitation behaviour has been verified in the Ti-Nb-C-N microalloyed steels. The Ti microalloyed steel after refining with 0.012 % Nb exhibited highly improved tensile strength without sacrificing ductility. According to further detailed SEM and TEM analysis, the improved mechanical properties of Ti/Nb microalloyed steel could be attributed to the larger solubility of Nb and Ti, inducing fine dispersion of the carbonitrides with particle size of 2 – 10 nm in the ferrite matrix. DOI: http://dx.doi.org/10.5755/j01.ms.21.4.9622

Effect of alloying on the phase composition of titanium carbonitride–titanium nickelide alloys

X-ray diffraction, electron microprobe analysis, electron microscopy, and chemical analysis are used to study the effect of alloying with zirconium, niobium, vanadium, and molybdenum on the phase composition of titanium carbonitride–titanium nickel cermets. It is shown that two-phase alloys containing alloyed titanium carbonitride and titanium nickelide can only be produced by alloying with zirconium. The addition of niobium, molybdenum, and vanadium leads to the formation of a third phase, namely, NbzNi, Mo(Ti,C), or V4Ni, in the alloy. A correlation between the phase composition of the alloys and the ratio of the energies of formation of titanium carbides and the carbides of alloying elements is found.

Thermodynamic model for precipitation of carbonitrides in microalloyed steels and its application in Ti–V–C–N system

Based on mass balance and solubility product equations, a thermodynamic model enabling the calculation of equilibrium carbonitride composition and relative amounts as a function of steel composition and temperature was developed, which provides a method to estimate the carbonitride complete dissolution temperature for different steel compositions. Actual carbonitride precipitation behavior was further verified in Ti–V–C–N microalloyed steel system. The model suggests that for higher [V] and [Ti] dissolved in steels, it is available to decrease the addition of C and N during alloy composition design. The resultant longer fatigue life of the modified steel could be attributed to the more [V] and [Ti] dissolved in the matrix, inducing finer dispersion of carbonitrides. Therefore, this model is proved to be effective in determining better chemical composition for high-performance steels, leading to possible reductions in the cost of production and improvements in the combined mechanical properties of the steels.

INVESTIGATION OF CHANGES IN THE COMPOSITION, STRUCTURE AND DISPERSION OF CHROMIUM CARBONITRIDE DURING STORAGE AND HEATING IN GAS MEDIA

The changes in the composition, structure and dispersion of chromium carbonitride during storage and heating in gas media are investigated. It is found that during annealing in argon and nitrogen at a temperature of 1273 – 1373 K carbonitride becomes carbide Cr3C2 , and during annealing in hydrogen – carbide Cr7C3 . The transformation of carbonitride into carbide Cr3C2 is accompanied by enlargement of the nanopowder that takes place in accordance with the mechanism of solid-state coalescence. Carbonitride interaction with atmospheric gases (oxygen and moisture) occurs in accordance with the adsorption-diffusion mechanism and it is accompanied by a significant increase in oxidation in the first 24 hours. The temperature at the beginning of oxidation in the air depends on the nanoscale and due to the change in particle size from 22 to 53 nm increases from 542 to 568 K. The size dependences for oxidation and the oxidation onset temperature are obtained.

Mechanical properties of stainless steel composites with titanium carbonitride consolidated by spark plasma sintering

In this paper, stainless steel–titanium carbonitride-based composites were fabricated and analyzed to utilize for bipolar plate in fuel cells. In order to study the size effect of titanium carbonitride on the mechanical and corrosion resistance properties of the composites, micro and nanosize titanium carbonitride powders were used. Stainless steel–carbonitride composites were prepared by spark plasma sintering and subsequently annealed at different temperatures up to 1100℃ to improve the morphological and mechanical properties. Various properties of the obtained samples were compared before and after annealing. It was shown that after heat treatment, the mechanical properties of the stainless steel–carbonitride composites improved due to the diffusion of titanium carbonitride particles into stainless steel. Addition of microsized titanium carbonitride powders was found to be effective to improve the mechanical properties, such as microhardness and compressive strength, of the composite. However, addition of nanosized titanium carbonitride powders led to an increase of corrosion resistivity of the composite. Physical properties, such as thermal and chemical stability of the obtained composite samples were investigated by microhardness tester, potentiostat, field emission-scanning electron microscope, EDX and X-ray diffraction.

Mechanochemical synthesis of Ti(C,N) nanopowder from titanium and melamine

Ti and melamine were used as raw materials to prepare Ti(C,N) powder by mechanochemical processing. Raman spectroscopy, XRD, TEM, XPS, elemental analyzer and ICP-MS were used to characterize the synthesized powder. The results showed that the chemical composition of titanium carbonitride after 100h of milling was Ti(C0.37N0.63)0.94 and the particle size was 10–20nm. Melamine was not only a reactant in the reaction, but also had a process control agent effect, which facilitated the generation of ultrafine Ti particles during the activated period. Melamine decomposed by means of ball milling and formed carbon and nitrogen-based active radicals which reacted with refined Ti particles and formed nano-scale Ti(C,N) powder.

Preparation of Ti Ternary Alloys by Addition of Si to Ti-Mo Alloy Scraps for Carbonitride Application

In this study, Ti-Mo-Si ternary alloy ingots were prepared by the addition of Si (0.25­2.0mass%) to Ti-10Mo alloy scraps in order to produce the raw materials for titanium carbonitride composites. To investigate the effects of Si addition, the prepared alloys were subjected to hardness, tensile strength, grain size, and phase analyses. The Si-added alloys showed no major changes in their O, N, and C impurity contents. Their hardness increased remarkably in proportion to an increase in the Si content, from 435Hv to 601Hv at 2.0mass%. The tensile strength increased with Si addition up to a maximum of 1.0mass%, reaching 883MPa, but after this peak, it decreased sharply because of the brittleness that arose by the formation of titanium silicide. [doi:10.2320/matertrans.M2014285]

Effect of Annealing Temperature on Electrochemical and Mechanical Properties of STS with Titanium Carbonitride Composites Synthesized By Spark Plasma Sintering

Stainless steel-titanium carbonitride based composites were fabricated and analyzed to utilize for bipolar plate in fuel cells. In order to study the size effect of the titanium carbonitride on mechanical and corrosion resistance properties of the composites, micro and nanosize titanium carbonitride powders were used. Stainless steel-carbonitride composites were prepared by spark plasma sintering and subsequently annealed at different temperatures up to 1100 °C to improve the morphological and mechanical properties. Various properties of the obtained samples were compared before and after annealing. It was shown that after the heat treatment, mechanical properties of the stainless steel-carbonitride composites were improved due to the diffusion of titanium carbonitride particles into stainless steel. Addition of microsized titanium carbonitride powders was found to be effective to improve the mechanical properties of the composite such as microhardness and compressive strength. However, addition of nanosized titanium carbonitride powders led to increasing of corrosion resistivity of the composite. Physical properties, such as thermal and chemical stability of the obtained composite samples were investigated by microhardness tester, potentiostat, field emission-scanning electron microscope, EDX and X-ray diffraction.

Thermodynamic calculation for the chemical vapor deposition of silicon carbonitride

Abstract In order to tailor the phase composition of silicon carbonitride (SiCN) by chemical vapor deposition or chemical vapor infiltration (CVD/CVI), it is necessary to set up a series of phase diagrams at a larger temperature range from 800 K to 1800 K using SiCl 4 , NH 3 , CH 4 /C 3 H 6 and H 2 as precursors. The equilibrium conditions of thermodynamic calculation were determined by temperatures, total pressures, dilute gas H 2 and molar ratios of reactants. CVD phase diagrams provide a qualitative description of phase composition, while the deposition efficiencies directly give the conversion extent from precursors to condensed phases. The low temperature phases (Si 3 N 4 , C) and high temperature phase (SiC) are also proved by thermodynamic calculation of CVD SiCN, which gives a clear way to conduct the experiments.

Phase Diagram Updates and Evaluations of the Al-Fe-P-Zn, Al-Fe-V-Zn, C-Fe-Mn-Nb and C-Fe-N-Ti-V Systems

Updates and evaluations of recent publications on the Al-Fe-P-Zn, Al-Fe-V-Zn, C-Fe-Mn-Nb and C-Fe-N-Ti-V systems are presented. Information on their phase diagrams includes isothermal sections and at 450 °C at 93% Zn for both the Al-Fe-P-Zn and Al-Fe-V-Zn systems, the solubility of NbC in austenitic C-Fe-Mn-Nb steel at 1150 °C, and the composition and fraction of titanium carbonitride in C-Fe-N-Ti-V steels on C and N content at 1100 °C.

Formation of carbonitride precipitates in hardfacing alloy with niobium addition

Niobium, as the most effective second-phase forming element, was added in the Fe–Cr13–C–N hardfacing alloy to get carbonitride precipitates. Morphology and composition of carbonitride in the hardfacing alloy were studied by optical microscopy, scanning electron microscopy, and electron probe microanalyzer. The thermodynamics and the effect on the matrix of the formation of carbonitride were also discussed. It was found that niobium carbonitrides are complex Nb(C, N) precipitate distributed on grain boundary and matrix of the hardfacing alloy. Under as-welded condition, primary carbonitride particles were readily precipitated from the hardfacing alloy with large size and morphology as they were formed already during solidification. Under heat treatment condition, a large number of secondary carbonitrides can precipitate out with very fine size and make a great secondary hardening effect on the matrix. As a result, addition of niobium in the hardfacing alloy can prevent the formation of chromium-rich phase on grain boundaries and intergranular chromium depletion. The Fe–Cr13–C–N hardfacing alloy with niobium addition has microstructure in which hard, fine niobium carbonitrides are homogeneously distributed in the matrix, and thus make a great secondary hardening effect on the matrix. And addition of niobium in the hardfacing alloy can prevent the formation of chromium-rich phase in grain boundaries and intergranular chromium depletion.