Gibbs free energies of formation of molybdenum carbide and tungsten carbide from 1173 to 1573 K

Iwai, Takashi; Takahashi, Ichiro; Handa, Muneo

doi:10.1007/bf02645000

Cited by 20 publications

(10 citation statements)

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“…[30] In addition, the diffusion barrier of carbon atoms on Cu is low, because carbon atoms interact mainly with the free-electron-like surface state in Cu, [31,32] and the interaction between graphene and Cu is very weak. [36] Consistent with our observation, carbon atoms are energetically more favorable to form carbide than graphene; [37,38] therefore, the preferentially formed tungsten carbide serves as a catalyst for graphene growth. [36] Consistent with our observation, carbon atoms are energetically more favorable to form carbide than graphene; [37,38] therefore, the preferentially formed tungsten carbide serves as a catalyst for graphene growth.…”

Section: Doi: 101002/adma201605451supporting

confidence: 82%

“…[33,34] W is a carbide-forming element, so that monolayer graphene can be formed on tungsten carbide but not on pure W. [35] Similar to Cu, self-limited growth of single-layer graphene can be achieved on tungsten carbide. [36] Consistent with our observation, carbon atoms are energetically more favorable to form carbide than graphene; [37,38] therefore, the preferentially formed tungsten carbide serves as a catalyst for graphene growth. [39,40] Different from Cu, however, tungsten carbide has a strong carbon affinity and interacts strongly with graphene.…”

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confidence: 82%

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Circular Graphene Platelets with Grain Size and Orientation Gradients Grown by Chemical Vapor Deposition

Xin

Fei

et al. 2017

Advanced Materials

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Monolayer circular graphene platelets with a grain structure gradient in the radial direction are synthesized by chemical vapor deposition on immiscible W-Cu substrates. Because of the different interactions and growth behaviors of graphene on Cu and tungsten carbide, such substrates cause the formation of grain size and orientation gradients through the competition between Cu and tungsten carbide in graphene growth.

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Section: Doi: 101002/adma201605451supporting

confidence: 82%

supporting

confidence: 82%

Circular Graphene Platelets with Grain Size and Orientation Gradients Grown by Chemical Vapor Deposition

Xin

Fei

et al. 2017

Advanced Materials

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“…Earlier values of the formation properties of tungsten carbides have been reviewed by Storms [27]. [30,31] and carbon [24,25] have been performed with variable success by Alekseev and Shvartsman [34], Orton [35] and Iwai et al [36]. The latter researchers took care not to oxidize the tungsten, by keeping the moisture level sufficiently low, and were able to obtain reasonable results in the range 1173-1573 K. By using more recent values of the Gibbs energy of formation for CH,(g) than Iwai et al [36], we find A,Ge(WC, for the presently assumed composition of the W,C, _-x phase.…”

Section: Discussionmentioning

confidence: 99%

“…[30,31] and carbon [24,25] have been performed with variable success by Alekseev and Shvartsman [34], Orton [35] and Iwai et al [36]. The latter researchers took care not to oxidize the tungsten, by keeping the moisture level sufficiently low, and were able to obtain reasonable results in the range 1173-1573 K. By using more recent values of the Gibbs energy of formation for CH,(g) than Iwai et al [36], we find A,Ge(WC, for the presently assumed composition of the W,C, _-x phase. In addition we have the result of Mah [l], A,H*(W,C, 298 K) = -(26.4 + 2.5) kJ mall', which can be combined with the present data when extrapolated to 1550 K. We have done so by assuming a linear heat capacity increase for W,C,,,,, from 76.75 J K-' mall' at 1000 K to 82 J K-' mall' at 2000 K. The results are, however, not mutually consistent.…”

Section: Discussionmentioning

confidence: 99%

Heat capacity and thermodynamic properties of ditungsten carbide, W2C1−x, from 10 to 1000 K

et al. 1988

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Thermodynamic properties of tungsten carbide, W&s,,, have been derived from heat capacities measured by adiabatic calorimetry in the range 10-1000 K on a sample rich in this phase. The standard entropy of WzCo.s33 was found to be 75.80 J K-i mol-' at 298.15 K and 159.8 J K-i mol-' at 1000 K. Thermodynamic formation values for W&e.,,, were deduced from the reported coexistence of this phase with tungsten and tungsten monocarbide at about 1550 K.

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“…Therefore, brittle fracture of the AISI 4135 steel after heat treating may be as a result of formation a relatively high content of chromium and molybdenum carbides. Formation of molybdenum carbides occurs at high temperatures during austenitising (Iwai et al, 1986) while formation of chromium carbides occurs at relatively low temperatures during tempering process (Fontana, 1987). About the formation of molybdenum carbides during tempering process there is not any thermodynamical data, but it is known that chromium carbide could not be formed at high temperatures (Fontana, 1987).…”

Section: Mmms 63mentioning

confidence: 99%

Failure analysis of heat treated HSLA wheel bolt steels

Nazari

Riahi

2010

Multidiscipline Modeling in Materials and Structures

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Purpose -The aims of this study is to analyze failure of two types of high-strength low-alloy (HSLA) steels which are used in wheel bolts 10.9 grade, boron steel and chromium-molybdenum steel, before and after heat treatment. Design/methodology/approach -The optimum heat treatment to obtain the best tensile behavior was determined and Charpy impact and Rockwell hardness tests were performed on the two steel types before and after the optimum heat treating. Findings -Fractographic studies show a ductile fracture for heat-treated boron steel while indicate a semi-brittle fracture for heat-treated chromium-molybdenum steel. Formation of a small boron carbide amount during heat treating of boron steel results in increment the bolt's tensile strength while the ductility did not changed significantly. In the other hand, formation of chromium and molybdenum carbides during heat treating of chromium-molybdenum steel increased the bolt's tensile strength with a considerable reduction in the final ductility. Originality/value -This paper evaluates failure analysis of HSLA wheel bolt steels and compares their microstructure before and after the loading regime.1. Introduction AISI 15B37 and AISI 4135 steels are of medium carbon high-strength low-alloy (HSLA) steels which are generally quenched and tempered after production (Hall, 2001). The most important alloying elements are chromium and molybdenum in AISI 4135 and boron in AISI 15B37 steels. Chromium and molybdenum displace time-temperature-transformation (TTT) diagrams to the right and limit the austenite single-phase region in iron-iron carbide phase diagram. Boron additives less than 0.003 wt% refine the grains without significant effect on TTT diagrams and cause high strength and hard steels (Avner, 1974;Tomita, 1990). Chromium-molybdenum steels (41xx series) have relatively low cost, good weld ability and ductility. These steels are common ones to produce super-safe bolts. In general, these bolt steels are used in automotive industry, as connectors of bridges parts, in frictional instructions and aerospace applications (Avner, 1974;Xue et al., 2003). For special applications, heat treatment of the bolts is necessary. The austenite transformation type, mechanical properties and final microstructure of bolts are strongly influenced by the dissolved alloying elements in parent austenite (Golozar, 1999). Chromium-molybdenum and boron steel bolts which are produced by cold forging in automobiles are utilized in several parts such as cylinder head bolt (12.9 grade), wheel bolt (10.9 grade), stud bolts and, etc. (Fastener's Handbook). Wheel bolts commonly fail under tensile stress. Therefore, wheel bolts not only must have an excellent tensile stress but also a rather good toughness to prevent catastrophic fracture.

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Gibbs free energies of formation of molybdenum carbide and tungsten carbide from 1173 to 1573 K

Cited by 20 publications

References 5 publications

Circular Graphene Platelets with Grain Size and Orientation Gradients Grown by Chemical Vapor Deposition

Circular Graphene Platelets with Grain Size and Orientation Gradients Grown by Chemical Vapor Deposition

Heat capacity and thermodynamic properties of ditungsten carbide, W2C1−x, from 10 to 1000 K

Failure analysis of heat treated HSLA wheel bolt steels

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