Effect Of Carbon Addition Research Articles

Effects of carbon addition on the microstructure, mechanical properties, corrosion resistance and tribological behaviour of Ti(C, N)-based cermets

In this work, the microstructure and properties of Ti(C, N)-based cermets with different carbon additions that were prepared by a powder metallurgy method were systematically studied through SEM, TEM, mechanical properties tests, electrochemical tests and friction tests. The results showed that the micromorphology of the core-shell structure in the cermets was strongly affected by carbon content. The increase in carbon addition can lead to a finer hard core phase and thicker rim phase in the cermets. In addition, both the fracture toughness and transverse rupture strength of cermets tended to increase first and then decrease with increasing carbon content, while hardness slowly decreased. The cermet with 0.3 wt% added carbon showed the highest fracture toughness (12.94 MPa · m1/2) and transverse rupture strength (1961 MPa). Furthermore, the corrosion resistance of the cermets decreased with increasing carbon addition in 0.2 mol L−1 H2SO4 solution during electrochemical tests on account of the alloying elements precipitating from the binder phase. Additionally, after room-temperature friction tests, the wear patterns of the cermets changed from abrasive wear to adhesive wear with increasing carbon addition due to the softening of the binder phase. However, plastic deformation and oxidation were the main wear behaviours of cermets in the high-temperature friction process.

Effect of carbon addition on stress rupture properties of a cast TiAl alloy

Two TiAl alloys, Ti–47.5Al–3.7(Cr, V, Zr) and Ti–47.5Al–3.7(Cr, V, Zr)–0.1C (at.%), were melted and cast with the same process, respectively. Microstructures with strongly oriented lamellae were both observed in these two alloys followed by hot isostatic pressing and heat treatment. Ti2AlC carbides were identified in the alloy with C addition. Stress rupture tests were carried out at 800 and 850 °C, with tensile stress from 220 to 400 MPa, respectively. It was shown that the alloy with C experienced much longer lives than the other, especially under the condition of 800 °C/260 MPa, 800 °C/300 MPa, 850 °C/220 MPa, 850 °C/240 MPa and 850 °C/260 MPa. Observation of ruptured specimens revealed that the microstructure stability was improved significantly in the alloy with C addition which is attributed to the strengthening effect of Ti–Al–C carbides. The Ti2AlC carbides mainly increased the resistance of dislocation passing through the interfaces and kept the integrity of the interfaces. And Ti3AlC carbide was formed during stress rupture process, which could not only effectively act as the barrier of dislocation movement inside the lamellae, but also strengthen the lamellae itself.

Unique effect of carbon addition on development of deformation texture through changes in slip activation and twin deformation in heavily cold-rolled Fe-3% Si alloys

The effect of carbon addition on the development of cold-rolling texture in heavily cold-rolled ultra-low carbon (ULC) 3% Si steel (<0.0005 mass% C-3.11 mass% Si) and low carbon (LC) 3% Si steel (0.016 mass% C-3.10 mass% Si) was investigated experimentally and theoretically. A higher carbon content in LC 3% Si steel led to the development of a {100}<011> cold-rolling texture compared with ULC 3% Si steel when the rolling reduction was 90%, which was the opposite tendency to that for conventional carbon steel without silicon content. According to slip bands observations at early stages of plastic deformation, carbon addition activated pencil-glide slip deformation on {110}, {112} and {123} slip planes and promoted deformation twinning, while only {110}<111> slip deformation was observed in ULC 3% Si steel. Crystal plasticity simulation implied that the combined effect of pencil-glide slips and twinning contributes significantly to the development of the {100}<011> cold-rolling texture in heavily cold-rolled LC 3% Si steel.

Stabilization of τ-phase in carbon-doped MnAl magnetic alloys

In this work, the effect of carbon addition on the L10 τ-phase stability in (Mn0.54Al0.46)100-xCx (x = 0–5) magnetic alloys are investigated. By microstructural analysis, single-phase and dual-phase microstructure are confirmed in 0 ≤ x ≤ 3 and x > 3 alloys, respectively. The solubility limit of carbon atoms in τ-phase of about 3 at.% is also determined by the characterization of the intrinsic magnetic properties and the crystal structure. The solid solution of carbon can significantly stabilize the thermodynamically metastable τ-phase, reflecting by the reversible τ→ε transformation path, and suppressing of the τ-phase decomposition effectively at high temperatures. The stabilized τ-phase by carbon doping exhibits higher magnetization in the as-milling state, with the highest magnetization for x = 3. After annealing at high temperature, the carbon-doped τ-phase is also more stable, resulting in the obvious improvement in magnetization. The magnetization of 86.7 emu/g under 30 kOe and the coercivity of 3.26 kOe are approached in the as-annealed x = 3 powders. These results clarify the effect of doping carbon on τ-phase stability in MnAl alloys and highlight the guidance and routine for high performance MnAl permanent magnets.

Evaluation of precipitation hardening in TiC-reinforced Ti2AlNb-based alloys

Ti2AlNb-based alloys with 0.0wt%, 0.6wt%, and 2.0wt% carbon nanotube (CNT) addition were fabricated from spherical Ti–22Al–25Nb powder by sintering in the B2 single-phase region. Phase identification and microstructural examination were performed to evaluate the effect of carbon addition on the hardness of the alloys. Carbon was either in a soluble state or in carbide form depending on its concentration. The acicular carbides formed around 1050°C were identified as TiC and facilitated the transformation of α2 + B2 → O. The TiC was located within the acicular O phase. The surrounding O phase was distributed in certain orientations with angles of 65° or 90° O phase particles. The obtained alloy was composed of acicular O, Widmanstatten B2 + O, and acicular TiC. As a result of the precipitation of carbides as well as the O phase, the hardness of the alloy with 2.0wt% CNT addition increased to HV 429 ± 9.

Microstructural evolution and mechanical performance of carbon-containing CoCrFeMnNi-C high entropy alloys

The effect of carbon addition up to 1.84 at.% on the mechanical performance and microstructure of a CoCrFeMnNi high-entropy alloy was studied. Both M23C6- and M7C3-type carbide particles were dispersed in the matrix and at grain boundaries in the cold-rolled and annealed carbon-containing alloy. The decrease of grain size in carbon-containing CoCrFeMnNi was predominantly due to grain boundary pinning by the carbide particles. With the addition of 1.84 at.% carbon, the yield stress of the annealed CoCrFeMnNi alloy increased from 253 to 527 MPa at the expense of its ductility. Carbon atoms strengthened the CoCrFeNiMn with 1.84 at.% carbon by grain size refinement (147 MPa) and enhanced friction stress (127 MPa) associated with interstitial carbon atoms and carbide particles. The strain-hardening rate as well as the yield strength increased at the early stage of deformation with increasing carbon content. Carbon addition had a beneficial effect on the mechanical properties by decreasing the grain size, increasing the friction stress associated with interstitial carbon, and enhancing twin stability.

CoCrFeMnNi 고엔트로피 합금에서 탄소 첨가 및 재결정열처리가 미세구조 및 기계적 특성에 미치는 영향

CoCrFeMnNi 고엔트로피 합금에서 탄소 첨가 및 재결정열처리가 미세구조 및 기계적 특성에 미치는 영향

Methane production increases with warming and carbon additions to incubated sediments from a semiarid reservoir

Methane production (MP) in aquatic systems is positively related to temperature and trophic state. Global warming and eutrophication are predicted to potentiate MP in freshwater reservoirs. The simultaneous impact of rising temperature and carbon and nutrient additions on MP were examined in a tropical semiarid hydropower reservoir. Sediments cores from 3 locations (profundal, littoral, and intermediate) with differing water depth were sectioned and slurries incubated at 20, 30, and 40 °C with or without additions of carbon, nitrogen, or phosphorus, or all combined. Maximal MP (4.2 μmol g DW−1 d−1), occurred under carbon addition, and mean MP was about twice as high than in the control, independent of temperature. The effect of carbon additions manifested differently at the 3 locations, with enhancement of MP greater in upper sediment layers of the profundal location and in deeper layers (4–8 cm) of littoral and intermediate locations. Without carbon addition, MP was slower and positive effects of warming were more frequent, especially in littoral. These results suggest that the combined effect of warming and land use changes, principally on carbon loads, will increase the MP and methane emissions potential in this semiarid reservoir. Differences in effects are linked to location in the reservoir.

Effects of carbon and nitrogen on precipitation and tensile behavior in 15Cr-15Mn-4Ni austenitic stainless steels

Precipitation behavior and tensile properties have been investigated for 15Cr-15Mn-4Ni austenitic steels containing 0.2wt% carbon and/or 0.2wt% nitrogen. During aging at 600–1000°C, precipitates such as σ, M23C6, and Cr2N were formed and time-temperature-precipitation diagrams were constructed. The type, size, and density of precipitates depended on the carbon and nitrogen contents. The nitrogen addition suppressed carbide formation while the effect of carbon addition on nitride precipitation was comparatively small. The evolution of tensile properties after aging is explained by the changes in solid solution strengthening and deformation modes caused by the precipitation. The precipitation of M23C6 slightly decreased yield strength and elongation while it increased ultimate tensile strength. On the other hand, the precipitation of Cr2N hardly affected tensile properties due to its low volume fraction.

Effects of Carbon Additives on the HRPSoC Performance of Lead Carbon Batteries and Their Low Temperature Performance

Effects of Carbon Additives on the HRPSoC Performance of Lead Carbon Batteries and Their Low Temperature Performance

Effect of carbon addition on the microstructure and mechanical properties of CoCrFeNi high entropy alloy

The effects of C element on the microstructure and properties of CoCrFeNiC x high entropy alloys ( x denoted the atomic fraction of C element at 0, 0.05, 0.1, 0.2, 0.3, and 0.5) were investigated. The equal molar CoCrFeNi alloy with FCC structure exhibits high ductility but weak strength. With the addition of C element, both the hardness and strength of the CoCrFeNiC x high entropy alloys increase as well as the wear resistance. The solution strengthening and the formation of hard carbide phase are the main factor for the improved strength, hardness and wear resistance of CoCrFeNiC x high entropy alloys.

Electrospinning of Carbon–Carbon Fiber Composites for High-Performance Single Coin-Cell Supercapacitors: Effects of Carbon Additives and Electrolytes

Carbon nanofibers incorporated with other carbon additives, i.e. acetylene black (ACB), hollow carbon sphere (HCS), and reduced graphene oxide sheets (rGO), were successfully produced by an electrospinning process. The influence of carbon additives was evaluated through the electrochemical performance of carbon-based nanofiber supercapacitors. The carbon additives with high sp2 content not only enhanced specific surface area but also improved electrical conductivity of the carbon nanofibers. A finely tuned 1 wt % ACB loaded to the carbon nanofibers provided a specific surface area of 116 m2 g–1, a specific capacitance of 209 F g–1 at 2 mA per cell, a specific energy of 14.2 Wh kg–1, a maximum specific power of 8.3 kW kg–1, and >99% capacity retention over 10 000 cycles in 1 M H2SO4 aqueous electrolyte. The carbon fiber composites here may be practically used in supercapacitors.

Effect of Carbon in Fabrication Al-SiC Nanocomposites for Tribological Application.

Aluminium-based hybrid composites are a new class of advanced materials with the potential of satisfying the demands in engineering applications. This paper describes the effects of carbon addition on the formation and properties of AMC with SiC nanoparticles reinforcement. The composites were produced via mechanical alloying followed by hot pressing. Three forms of carbon, graphite (GR), multiwalled carbon nanotubes (CNTs), and, for the first time, glassy carbon (GC), were used for the hybrid composites manufacturing and compared with tribological properties of Al-SiC composite without carbon addition. GC and CNTs enhanced formation of Al-SiC composite particles and resulted in a homogeneous distribution of reinforcing particles. On the other hand, GR addition altered mechanochemical alloying and did not lead to a proper distribution of nanoparticulate SiC reinforcement. Hot pressing technique led to the reaction between Al and carbon as well as SiC particles and caused the formation of Al4C3 and γ-Al2O3. The subsistence of carbon particles in the composites altered the predominant wear mechanisms since the wear reduction and the stabilization of the friction coefficient were observed. GC with simultaneous γ-Al2O3 formation in the hybrid Al-SiC(n)-C composites turned out to be the most effective additive in terms of their tribological behaviour.

Pressureless sintering of binderless tungsten carbide

The aim of this study was to produce dense, single phase polycrystals. The research was carried out on the submicron tungsten carbide powder without additives, with either a carbon or tungsten additive and on the powder with both additives. The primary task of carbon was to reduce surface oxide impurities which passivate WC grains; tungsten in turn bounds free carbon in the WC. The authors manufactured fine-grained, dense (96–98% T.D.) and single-phase WC polycrystals, using the technique of pressureless sintering at the temperature not exceeding 2000°C. A positive effect of carbon addition on tungsten carbide sinterability was observed, whereby a dense, fine-grained polycrystals can be obtained at 1900°C. It was also observed that a significant excess of temperature of sintering process resulted in a strong abnormal grain growth of WC grains.

Effect of Carbon Addition on the Cast and Rolled Microstructures of FeCoCrNiMn High Entropy Alloys

In this study, the effect of carbon addition the cast and rolled microstructures of Cantor alloy type FeCoCrNiMn high entropy alloys. Both as-cast FeCoCrNiMn and FeCoCrNiMnC0.1 alloys have dendritic microstructure. Small particles, which may be associated carbon addition exist in the dendrite arms in FeCoCrNiMnC0.1 alloy. After homogenization treatment at 1327K for 24 hrs., dendritic structure was completely eliminated after annealing. Dendritic structure was converted to the structure with elongated grains, especially for carbon added FeCoCrNiMnC0.1. The development of elongated grains is associated with the direction of the primary arms in the dendritic structure. Carbides are segregated at the grain boundaries in FeCoCrNiMnC0.1 alloy. It also appears that growth of grains is impeded by the segregation of carbides. It is apparent that the grain boundary precipitates are Cr-rich. Both the strength and ductility of FeCoCrNiMnC0.1 increased over FeCoCrNiMn with the addition of 0.1 wt. % carbon. The increase of ductility in FeCoCrNiMnC0.1 may be caused by the rapid hardening in FeCoCrNiMnC0.1 due to dislocation-solute interaction.

Effects of carbon addition on wear mechanisms of CoCrMo metal-on-metal hip joint bearings

The wear behaviors of biomedical CoCrMo prosthetic alloys containing various amounts of carbon were investigated using a standard hip joint simulator in a simulated body fluid. A few chunks and punctate σ-phase precipitates were observed in the low-carbon (LC) alloy; these were responsible for the abrasion and run-in wear. Increasing the carbon content led to greater precipitation of globular M23C6-type carbides. As a result, lower wear loss was observed in the high-carbon (HC) alloy. However, the Student's t-test analysis on wear loss indicated that there was no significant difference in wear loss between the LC-LC and HC-HC combinations. Surface fatigue caused by torn-off of Mo-rich carbides was the dominant wear mechanism in the HC alloy. Further, Cr-rich carbides prevent three-body abrasion and increase the wear resistance.

Wear resistant boron carbide compacts produced by pressureless sintering

Boron carbide compacts were produced by pressureless sintering at 2200°C/2h and 2250°C/2h in Ar atmosphere, using a starting powder with a particle size smaller than 3µm. Effects of carbon addition (3.5wt%) and methanol washing of the starting powder were investigated on the densification, Vickers hardness, and micro-abrasive wear resistance of the samples. The removal of oxide phases by methanol washing allowed the production, with no sintering additive, of highly densified (93.6% of theoretical density), hard (25.4GPa), and highly wear resistant (wear coefficient =2.9×10–14m3/N.m) boron carbide compacts sintered at 2250°C. This optimized combination of properties was a consequence of a reduced grain growth without the deleterious effects associated to the carbon addition. Methanol washing of the starting powder is a simple and general approach to produce, without additives, high quality, wear resistant boron carbide compacts by pressureless sintering.

Effect of Carbon Addition on Magnetic Order in Mn–Al–C Alloys

The near-equiatomic Mn–Al alloys are considered for possible applications as rare-earth-free permanent magnets due to the existence of a ferromagnetic $\tau $ -phase with $\text{L}1_{0}$ crystal structure and other attractive physical properties. However, this tetragonal phase is metastable and can only be obtained from a hexagonal $\epsilon $ -phase enriched in manganese. The partial atomic disorder can results in antiferromagnetic coupling of the Mn atoms occupying different sublattices. Moreover, the carbon addition, used to improve phase stability and coercivity, leads to the deformation of the unit cell and can affect the Mn–Mn coupling. To clarify this question, a series of magnetic measurements and neutron diffraction (ND) experiments in a wide temperature range was carried out on the Mn55Al45 alloys doped with a small quantity of C. The materials were prepared by melt-spinning and subsequent annealing. Different methods of carbon introduction were tried, the best results were obtained by melting Mn and Al with Mn23C6. The structural and magnetic properties of the ferromagnetic and paramagnetic $\tau $ -phase as well as the precursor $\epsilon $ -phase were determined. The average magnetic moments on two sublattices were analyzed using the Weiss plot of the magnetometric data and the Rietveld refinement of the ND data. The dependence of the magnetic moments on the C content and temperature is reported. Ferrimagnetic behavior of the Mn–Al alloys with excess of manganese, caused by antiferromagnetic coupling and responsible for the decrease of magnetization with increase of Mn content, was confirmed.

Establishment of native grasses and their impact on exotic annuals in degraded box gum woodlands

AbstractRestoration goals often involve the addition of new species to resident, degraded communities but in box gum woodlands such restoration is often constrained by competition from persistent exotic annuals that control critical ecological processes. Nutrient reduction (via carbon addition) and seed bank depletion are two approaches to reduce competition from exotic annuals but to be effective these treatments must allow establishment of species such as native grasses. This experiment was conducted in two degraded Austrostipa understoreys in the box gum woodlands of south‐east Australia. It compares the effects of carbon addition (sugar), seed depletion (spring burning or spring grazing) and combinations of carbon addition and seed depletion treatments on the establishment of C3 and C4 native grasses, and measured the effects of their establishment on soil nitrate concentration and exotic annuals. Treatments that reduced exotic annual abundance did not increase initial germination of the C4 native grasses, Bothriochloa or Themeda. However, sugar increased seedling survival of Themeda and Bothriochloa and grazing increased seedling survival of Bothriochloa, presumably by reducing effects of exotic annuals. Poa and Rytidosperma (C3 native grasses) failed to establish. Although we were unable to detect any reduction in soil nitrate concentration, swards with successful recruitment of C4 grasses suppressed exotic annuals more than the Austrostipa‐only swards at one site (the other was affected by wildfire). Further, Austrostipa‐Themeda swards were more effective than Austrostipa‐Bothriochloa for suppressing exotics, pointing to a role for both functional and species identity in the degree of resistance conferred.

Improvement in microstructure and mechanical properties of Ti(C,N)-Fe cermets with the carbon additions

In this study, the effects of carbon additions on the microstructure, hardness, transverse rupture strength and abrasion resistance of Ti(C,N)-Fe cermets manufactured by powder metallurgy method were investigated by scanning electron microscopy, X-ray diffraction and mechanical properties tests. The results show that the microstructure of sintered Ti(C,N)-Fe cermets exhibits the homogeneous distribution of Ti(C,N) hard phase when 1.0 wt% carbon was added into the cermets. The transverse rupture strength of cermet can reach the peak of 2435 MPa and the fracture morphology can include a vast of transgranular fracture. Moreover, the comprehensive performance of Ti(C,N)-Fe cermets can improve significantly through the heat-treatment process. The hardness and transverse rupture strength of cermets after heat-treatment are 70.0HRC and 2483.2 MPa. The Ti(C,N)-Fe cermets have a potential application in machining.