Kinds Of Carbides Research Articles

A Study of the Carbides in High-Speed Steel Rolls

Carbides in HSS roll were studied systematically. The results showed that there were two kinds of carbides in HSS roll, 1st and 2nd carbides. 1st eutectic carbides included the chrysanthemum-like MC mainly consisting of V and the plate-like M2C rich in Mo. 2nd carbides were complex carbides, concentrating Fe, Cr, Mo and V elements. The morphology, distribution and alloy concentration of the 1st eutectic carbides were studied using OM, SEM and EDS. During heat treatment, evolution of the 1st eutectic carbides was analyzed. It was found that the MC carbides had no change in morphology, components and distribution, while the M2C carbides decomposed to M6C and MC. In order to improve the properties of HSS, a method of increasing solidification rate was defined to refine the eutectic carbides. After refinement, the eutectic carbides distributed both along the grain boundaries and inside the grains.

Influence of Holding Time After Deformation on Bainite Transformation in Niobium Microalloyed Steel

Using Gleeble-1500 system, the influence of holding time on bainite transformation in deformed niobium microalloyed steel during continuous cooling was analyzed, and the carbides in upper bainite were also systematically researched. The results show that the occurrence of the static recrystallization decreases the amount of bainite with an increase in the holding time and the emergence of retained austenite (RA) with the longer holding time. Two types of carbides were observed in upper bainite with regard to their precipitation sites. They either existed between the bainite ferrite laths or co-existed with RA. The formation mechanism of two kinds of carbides was analyzed by combining TEM micrographs with the model.

The Influence of Post-Quenching Deep Cryogenic Treatment on Tempering Processes and Properties of D2 Tool Steel. Studies of Structure, XRD, Dilatometry, Hardness and Fracture Toughness

A significant increase in durability of cryogenically treated tools after quenching was reported by a number of publications [1, 2]. As research studies show [4, 5, 6, 7], the main reason for this is the kind of carbides precipitated during tempering at temperature range of 150 –200 0C, which is different than in the case of conventional treatment. These carbides are finer and more evenly distributed in the matrix of steel. The number of carbides is higher than in conventionally treated steels because of higher fraction of martensite in cryogenically treated steels produced by retained austenite transformation at cooling to deep cryogenic temperatures. The number of carbides precipitated from martensite at low temperatures of tempering is proportional to shrinkage produced at the same temperatures of tempering. Calculations on the basis of dilatometric experiments show that the shrinkage difference between the same D2 steel cryogenically and conventionally treated is higher than that which results from the increased fraction of martensite in cryogenically treated steel. The XRD studies of cryogenically treated steel show a presence of two kinds of martensites differing in tetragonality. Low temperature tempering of cryogenically treated steel produced two types of carbides – ε carbide and η carbide. The conventionally treated steel consists of one kind of tetragonal martensite and one kind of carbide - the ε carbide. The hardness of cryogenically treated samples was somewhat higher than in conventionally treated ones, while fracture toughness of conventionally treated samples was somewhat higher than in cryogenically treated ones. The results obtained were discussed in reference to literature data.

Micro-segregation on the Mono-variant Line of an Iron-Carbon-Chromium Ternary Alloy

To examine an effect of diffusion in the solid on the micro-segregation on a mono-varinat line, a directional solidification experiment has been carried out in an iron–carbon–chromium ternary alloy. In an iron–carbon–metal ternary alloy, carbon is an interstitial solute in an iron-base solution (austenite or ferrite) and the diffusivity in the solution is not negligible, while the third metallic element in the iron-base solution is usually substitutional solute and its diffusivity is negligible compared with that of carbon. The second phase of the ternary alloy is usually a kind of carbide, and the diffusivity of carbon or the third metallic element can be neglected because of the strength of the bonding forces of the atoms. In such a situation with dendritic-eutectic mode, a micro-segregation model on the mono-variant line has been introduced, and it has been predicted that the progress of the solidification might terminate before reaching the three-phase eutectic point. If we assume a Scheil-type model of micro-segregation on a mono-variant line, the composition of the residual liquid will reach the terminal (for example, three-phase eutectic) point.To confirm this prediction, an experiment has been carried out in an iron–carbin–chromium alloy. The initial composition is 3.17 mass% C and 25.6 mass% Cr and very near the eutectic valley of austenite–(Fe, Cr)7C3. With no diffusion of carbon in the austenite phase, the solidification will change to austenite–(Fe, Cr)3C eutectic reaction through the peritecto-eutectic point. With the effect of carbon, using the model, the solidification will end before reaching the peritecto-eutectic point and (Fe, Cr)3C formed during solidification will not be found. The metallographical observation revealed the exsistence of (Fe, Cr)7C3 phase but did not reveal the exsistence of (Fe, Cr)3C phase. The EPMA measurement between the dendritic arms showed that the measured minimum chromium compositions inside the austenite agree with the predicted values within an experimental error and uncertainties of parameters of the system. The identificatin of the phases by using XRD indicated that austenite–(Fe, Cr)3C eutectic did not form, as was predicted. These results suggest the validity of the model of micro-segregation on the mono-variant line in an iron–carbon–metal ternary system.

Carbon redistribution during sigma phase precipitation in high purity 25Cr-10Ni-0.35C-Si stainless steels

The role of carbon and chromium carbide during sigma phase precipitation in austenitic 310 stainless steels can be summarised in three main points: (a) carbide is a chromium source for sigma, (b) carbon is not soluble into sigma, (c) sigma precipitation can occur when (i) the carbon content in the matrix is lower than a critical value and (ii) the chromium-equivalent is higher than a critical value. These contradictory conditions ask the question of the distribution of carbon during sigma precipitation and chromium carbide dissolution which releases carbon insoluble into sigma. Several intermediate phases have been described in industrial alloys which contained carbide formers such as niobium or titanium but the redistribution of carbon has not been discussed when these elements are absent. In the present work, model alloys (25 Cr, 10 Ni, 0.35 C) containing only chromium as carbide former have been prepared and heat treated in the interval 750-850°C. Several phenomena occurring simultaneously have been observed: intergranular and transgranular precipitation of chromium carbide, in parallel with massive and lamellar sigma phase precipitation. The distribution of carbon between different kinds of carbide is discussed.

Molybdenum nitride and carbide catalysts for ammonia synthesis

High surface area molybdenum nitride (γ-Mo 2N) and two kinds of carbides (α-MoC 1− x or β-Mo 2C) were prepared by the temperature programmed reaction with NH 3 for the former sample, and with CH 4+H 2 mixed gas for the latter samples. To prepare γ-Mo 2N, the precursor MoO 3 was heated up to 973 K and held for 2 h under NH 3 flow. To prepare α-MoC 1− x , the precursor γ-Mo 2N was heated up to 973 K and held for 2 h under CH 4+4H 2 flow. To prepare β-Mo 2C, the precursor MoO 3 was heated up to 973 K and held for 2 h under CH 4+4H 2 flow. The surface areas of γ-Mo 2N and α-MoC 1− x were about 140 m 2 g −1; on the other hand, that of β-Mo 2C was 32 m 2 g −1. However, β-Mo 2C was most active among those samples and was as active as the doubly-promoted iron catalyst. The stability of those catalysts treated with the reactant gas at 873 K was examined under the reaction condition. The activity of α-MoC 1− x was decreased because this phase was not stable. CN atomic exchange occurred. γ-Mo 2N and β-Mo 2C were more stable than α-MoC 1− x . To improve the catalytic activity, alkali was added. Addition of caesium did not affect the formation of γ-Mo 2N and α-MoC 1− x , and the activities were somewhat improved. On the other hand, Mo metal was formed instead of β-Mo 2C by the carburization from MoO 3 with Cs added.

Kinetics of Carbide Layer Forming on the Surface of Steel in Molten Systems

A mathematical model of kinetics of carbide layer formed on the surface of steel in fused system was set up with the theory of non-stable diffusion mass transfer and regular solution sub-lattice. This model was analyzed and testified by the experiments in which the VC layers were formed on four kinds of steels as steel 45, 4Cr5Mo-SiV1, T10, and Crl2MoV immersed in the V2O5-Na2O-B2O5 fused system with the reducing agent of silicon. The results showed that there was a good agreement between the model and the experimental results; the growth speed of carbide layer depended on the factors of carbon activity in substrate, treatment temperature, kinds of carbides and its structure.

ＳｉＣｐ／Ａｌ‐Ｔｉ合金溶湯間反応によるｉｎ ｓｉｔｕＴｉＣｐ／アルミニウム複合材料の製造と機械的性質

A novel technique has been developed for fabricating in situ formed TiCp/Al composites. In this process, fairly stable TiC particles were in situ synthesized in liquid aluminum by the interfacial reaction between an Al-Ti melt and SiC, which is a comparatively unstable carbide from the view-point of thermodynamics. It is possible in the present process to generate TiC particles of nearly 1μm in diameter, even utilizing SiC of 14μm as raw material. However, the dispersion behavior of TiC particles in the matrix depends on the size of the raw material SiC. Decomposing finer SiC makes the dispersion of_TiC particles more uniform and the mechanical properties of composites are improved accordingly. The structure of in situ composites and their mechanical properties are affected by the fabrication temperature and the stirring time. It has been found that the most suitable condition for fabrication should be applied depending on the size of the raw material, even if the same kinds of carbide are used. Furthermore, although Al-Ti-Si system intermetallic compounds were detected in a TiCp/Al-Si composite which was fabricated by conventional melt stirring method, these compounds can not be observed in a TiCp/Al-Si composite made by this in situ production method. Hence, the mechanical properties of the in situ TiCp/Al-Si composite are superior to those of the conventional TiCp/Al-Si composite.

Phase Analysis of a Laserglazed Rene’N4 Superalloy

It is the first time that the phases in laserglazed single crystal nickel-base superalloy Rene'N4 have been studied systematically. The results show that there are three kinds of carbides and finely dispersed gamma' phase, as well as the gamma/gamma' eutectic in the microstructure, and the carbides are f.c.c TiC, TaC and hexagonal WC. These carbides and gamma/gamma' eutectic are distributed in the interdendritic regions. The cooling rate strongly affects not only the morphology of TiC but also the morphology and size of the gamma' phase. The morphology of TiC changes from the as-cast blocky form to dendritic and finally to a well-branched chrysanthemum-like form as the cooling rate is increased. At the same time, the size of gamma' becomes smaller and the morphology of gamma' changes from cubic to rounded-cubic. After rapid solidification, the as-cast well-developed mushroom-like gamma/gamma' eutectic alters into featherlike. The existence of gamma' and gamma/gamma' eutectic indicates that their precipitation rates are too large to be able to suppress their precipitations under a rapid solidification condition.

ＶとＣｒまたはＮｄとＣｒを含む溶融ほう砂浴中で鋼に形成された複合炭化物

When carbon steels had been were immersed in molten borax baths containing both Fe-V (or Fe-Nb) and metallic Cr at 850-1050°C, two kinds of carbides were observed in the layer formed on the steel surface. One carbide was VC (or NbC) crystal structure containing small amount of Cr element, and the other was M7C3 containing some V (or Nb) and Fe elements. The M7C3 phase increased with the addition ratio of Cr to V (or Nb) in the baths, and was generally formed in the layer contacting the substrate. The activation energy for the growth of the complex carbide layer was smaller than that of VC (or NbC) layer formed in baths containing V (or Nb), and larger than that of Cr7C3+Cr23C6 layer formed in baths containing Cr. The complex carbide layer showed as high hardness and excellent wear resistance as VC layer, and as good oxidation resistance as Cr carbide layer.

A high-resolution Auger electron spectroscopy study of the intergranular fracture of a temper-embrittled steel

One of the earliest uses of Auger electron spectroscopy was the analysis of the intergranular fractures to determine how segregated impurities produce intergranular embrittlement. As spatial resolution improved it became evident that the impurities were inhomogeneously distributed among individual intergranular facets. Further improvement in the spatial resolution now with primary beam diameter down to 0.1 μm has revealed that impurity distribution even on individual intergranular facet can be highly nonuniform. In this study we report on a CrMoV steel steam turbine rotor embrittled by P segregation during 20 years of service revealing that the grain boundaries were mainly covered by two kinds of carbides: one Cr rich and the other Mo rich. The P level at the Cr rich carbides was generally lower than on the carbide-free regions.

Ｆｅ‐Ｃｕ‐Ｂ系焼結材料 ＩＩ Ｆｅ‐Ｃｕ‐Ｂ系焼結材料の機械的性質と冷間鍛造性

The objects of this report are to examine the mechanical properties of Fe-Cu-B based sintered alloys containing some other elements such as carbon or some kinds of carbides, and to examine the cold-formability of Fe-Cu-B base sintered compacts and the mechanical properties of cold-forged compacts.After carburizing, quenching and tempering, the sintered compacts composed of F-e-5Cu-0.15B-0.65Cr-0.1C show a tensile strength of 900 MPa at the density of 7.2g/cm3.As these sintered compacts show high elongation, it is possible to make parts by cold-forging using these materials.After carburizing, quenching and tempering, the tensile strength of cold-forged compacts composed of the above mentioned material is more than 1200 MPa.

噴霧粉より作られた高速度鋼の耐摩耗性

This study is aimed to investigate the wear resistance of high speed steel made from atomized powders. The specimens for wear test were prepared by canning extrusion of the SKH9 steel powders with or without various kinds of carbide or nitride powders. Wear tests were, also, carried out for commercial forged SKH9 steel and commercial isostatically compressed SKH9 steel made from atomized powders. The results are summarized as follows:1) At high sliding speed, the high speed steel made from powders shows better wear resistance than the forged high speed steel. But at low sliding speed, no significant differences are found between them.2) Addition of TiC, WC, TiN or AlN increases wear resistance of high speed steel at both high and low sliding speeds.3) Especially, TiC and TiN are very effective in improving wear resistance.

恒温変態させたMo鋼の共析組織に現われる炭化物について

Carbides formed in the isothermally transformed molybdenum steels have been studied in the temperature range 675°∼550°C. Two kinds of carbides, M3C and M23C6, appeared depending on chemical composition (Mo/C ratio) and/or isothermal transformation temperature. In steels with Mo/C ratios less than 1.0, M3C carbide precipitates over the temperature range 675°∼550°C, while in steel with the Mo/C ratio equal to 1.0 M23C6 carbide is formed at or above 650°C and M3C carbide at or below 625°C.The orientation relationships between M23C6 carbide and ferrite have been determined using transmission electron microscopy and the electron diffraction technique. Several sets of orientation relationships instead of one characteristic relationship are observed, suggesting that M23C6 carbide and ferrite are formed separately in austenite.

Carbides in Molybdenum Steels

Carbides isolated electrolytically from molybdenum steels were studied by x-ray, chemical, and thermomagnetic analyses and by electron-microscopic observations in order to investigate the nature of carbides in the steels and to determine the carbide-phase diagram of molybdenum steel below the eutectoid temperature. In the case of thermal treatment at 700 deg C for 24 hr, the carbides formed by tempering are quite different from those formed by isothermal transformation. But, after a prolonged treatment at 700 deg C, carbides in both the structures tend to approximate each other gradually, and five kinds of carbides, M/sub 3/C, M/sub 23/C/sub 6/, , M/sub 2/C, and M/sub 6/C, appear, as the atomic rat io Mo: C in the steel increases. Among these carbides, M/sub 3/ C and M/sub 23/C/sub 6/ are ferromagnetic, of which the Curie points are 215to 181 deg C and 312 to l83 deg C, respectively. The composition ranges of carbides in molybdenum steels at 700 deg C are as follows. M/sub 3/C: 6.67% C, 0 to 2.5% Mo; M/sub 23/C/sub 6/: 5.0 to 6.0% C, 5.5 to 13.5% Mo; :5.5to 6.0% C, 30to 37% Mo; M/sub 2/C: ab0ut 6% C, 70% Mo; and M/sub 6/C:2.5to 2.8% C, 45to 62%more » Mo. (auth)« less

Study of Metallic Carbides by Electron Diffraction Part IV. Cobalt Carbides

Thin cobalt films formed by evaporation were carburized in town gas at temperatures below 550°C for several hours. Electron diffraction studies of these films confirmed the existence of two kinds of carbide, Co 2 C and Co 3 C. Co 2 C is an orthorhombic crystal with lattice constants a =2.910, b =4.469 and c =-4.426 A, and has a distorted c.p.h. structure. The lattice relation between Co 2 C and Co is (001) Co 2 C //(00.1) α-Co //(111) β-Co and [100] Co 2 C //[10.0] α-Co //[10\bar1] β-Co . Co 2 C is formed at temperatures in a range 450°∼500°C, and decomposes gradually to α-Co containing stacking faults and graphitic carbon at temperatures in a range 450°∼470°C. Co 3 C is an orthorhombic crystal with lattice constants a =4.483, b =5.033 and c =6.731 A and is isomorphous with cementite (Fe 3 C). The lattice relation is (1\bar21) Co 3 C //(10.1) α-Co //(100) β-Co , and [111] Co 3 C //[0\bar1.0] α-Co //[001] β-Co . Co 3 C is formed at temperatures in a range 450°∼500°C and decomposes gradually to α-Co contain...

18-8Tiステンレス鋼中に析出する炭化物の形態的分類とその析出条件について

Phase changes at elevated temperature in 18-8 stainless steel stabilized by titanium were observed through their precipitates. The extracted carbides were analysed under an electron microscope. The precipitates were morphologically classifed and their constituents were analysed by selected-area electron-diffraction. The mode of their precipitation in steel was certified and the relation between heat treatment and the precipitates was studied. The test pieces were heat-treated under the conditions covering the temperature range from 650 to 1200°C and the heating time range from 30 second to 567 hours after solution treatment at 1300°C for one hour. As the results, three courses of precipitation were concluded, that is, the one was on the grain boundary; the second was in the grain and the third was on the twin boundary. It was shown that since a particular carbide was observed after each heat treatment, the metallographical characteristics of 321 type stainless steel were specified by the kinds of carbides.

モリブデン鋼中の炭化物について

Carbides isolated electrolytically from molybdenum steels were studied by x-ray, chemical, and thermomagnetic analyses and by electron-microscopic observations in order to investigate the nature of carbides in the steels and to determine the carbide-phase diagram of molybdenum steel below the eutectoid temperature. In the case of thermal treatment at 700 deg C for 24 hr, the carbides formed by tempering are quite different from those formed by isothermal transformation. But, after a prolonged treatment at 700 deg C, carbides in both the structures tend to approximate each other gradually, and five kinds of carbides, M/sub 3/C, M/sub 23/C/sub 6/, , M/sub 2/C, and M/sub 6/C, appear, as the atomic rat io Mo: C in the steel increases. Among these carbides, M/sub 3/ C and M/sub 23/C/sub 6/ are ferromagnetic, of which the Curie points are 215to 181 deg C and 312 to l83 deg C, respectively. The composition ranges of carbides in molybdenum steels at 700 deg C are as follows. M/sub 3/C: 6.67% C, 0 to 2.5% Mo; M/sub 23/C/sub 6/: 5.0 to 6.0% C, 5.5 to 13.5% Mo; :5.5to 6.0% C, 30to 37% Mo; M/sub 2/C: ab0ut 6% C, 70% Mo; and M/sub 6/C:2.5to 2.8% C, 45to 62%more » Mo. (auth)« less

高クロム鋼の材質に及ぼすTiの影響（第2報）18%Cr鋼の諸性質に及ぼすC及びTiの影響

Using 18% Chromium steels containing 0.03∼0.27%C and 0∼3.26%Ti, several properties were studied. The self hardening property vanishes with the addition of more than 0.25% of titanium, irrespective of carbon , and with further addition of titanium the hardness gradually increases. The temper-hardening is observable in specimens containing more than 2.5% titanium and 10 times carbon content. The grain size of ferrite is refined and its growth at high temperature is retarded with the addition of about 0.25%Ti. One or two kinds of carbide, Cr4C and TiC, are obsevable, according to titanium and carbon contents. Acid-resistivity with conc. boiling HNO3 solution and corrosibility with 3%NaCl solution were tested, Impact resistance markedly increases with the addition of 0.25∼0.50%Ti, irrespective of carbon content and decreases with further addition of titanium.