Carbon Content Of Alloy Research Articles

Fe-C-Cr-Nb合金の凝固組織

The freezing processes and solidification structures of Fe-5%Cr and Fe-15%Cr alloys with 0.5 to 4.7%C and 0 to 7.5%Nb were investigated metallographically. The distribution of alloying elements were also studied by use of E.P.M.A. to clarify the behavior of elements during solidification. The constitutional diagrams for liquidus surfaces of Fe-5%Cr-base alloys and Fe-15%Cr-base alloys were established. In the 5%Cr system primary δ, γ, NbC and M3C phases and eutectic reactions of Liquid→(γ+NbC), Liquid→(γ+M3C) and Liquid→(γ+NbC+M3C) appeared. Primary δ, γ, NbC and M7C3 phases and eutectic reactions of Liquid→(γ+NbC), Liquid→(γ+M7C3) and Liquid→(γ+NbC+M7C3) occurred in the 15%Cr system. Primary niobium carbides grew dendritically and eutectic niobium carbides crystallized in the shape of petal. The amount of NbC increased and that of M3C and M7C3 decreased with increasing niobium content of alloy. During solidification niobium was preferentially partitioned to primary and eutectic NbC, and chromium to M7C3 crystals. The partition ratios of niobium and chromium to primary γ were 0.02 to 0.01 and 0.93 to 0.72, respectively. They decreased with the increase in the carbon content of alloy. The addition of 0.3%Ti to the melt nodularized both primary and eutectic niobium carbides, because many tiny titanium carbide particles precipitated at higher temperatures nucleated the niobium carbides.

The effect of boron and carbon on the microstructural chemistries of two wrought nickel base superalloys

The so-called “Boron-Carbon Effect” obtained by reducing the alloy carbon content and increasing the boron content only introduces one new phase, i.e., the precipitation of blocky, Mo-rich M 3B 2. In UDIMET 720 blocky MC particles are observed as well as the M 3B 2 particles although the carbon content is only 0.035 weight percent. The grain boundary phase is essentially the same structure, a boro-carbide which is designated M 2 3 (CB) 6, in both UDIMET 710 and UDIMET 720. Indirect evidence for increased boron in the M 2 3 (CB) 6 in UDIMET 720 is the change in metallic element content, compared to UDIMET 710, of the grain boundary phase. The increased molybdenum content and reduced chromium content indicates the M 2 3 (CB)may be more boron rich in UDIMET 720. The change in metallic element content in the M 2 3 (CB) 6 results in a greater concentration of chromium in the γ matrix of UDIMET 720 than in UDIMET 710. This may account for the improved environment sensitive mechanical behavior of the former alloy. UDIMET 720 also displays ultrafine γ′ after heat treatment which indicates that boron may promote the stability of small γ′ particles which may in turn improve stress rupture behavior. The minor differences in nonmetallic element content induces significant changes in the chemical segregation of the metallic elements. Description of these differences will be reported in a future publication (13).

The Two-Phase Region of TiC-Ni Alloy in Relation to the characteristics of Starting Titanium Carbide Powders

The range of two-phase region and the binder or carbide phase composition in the phase region in TiC-Ni alloy were examined in relation to the characteristics of starting titanium carbide powders. The starting powders were prepared from TiO2 and TiH2. Produced titanium carbides have various carbon contents from 17.20 to 19.55%. Five sorts of TiC-30%Ni alloy systems, each different, according to the starting powders used, were vacuum-sintered at 1400°C for 1.5 hr. In each alloy system, the carbon content was strictly controlled and the various alloys with various carbon contents were sintered.The results obtained were as follows; it was concluded that the range of two-phase region or the compositions of both phases in the alloy systems were not affected by the characteristics of starting powders so far as the alloy systems could successfully be sintered. For example, the two-phase region was found in such cases to exist in the range of about 18.1-19.3% in carbide (converted values of carbon content of alloy to carbide). The maximum carbon content of this 19.3% (actual carbon content in carbide phase, 19.2%) appeared to be controlled by the dissolution of nickel in carbide. It has been suggested that the reasonable combined.carbon of starting titanium carbide powder needed for TiC base cermets should be in the range of at most about 18.5-19.2%, when the oxygen content in starting powders is less than about 0.1%.

Relations between Some Properties of Sintered WC-10%Ni Alloy and its Binder Phase Composition

Relations between basic properties of sintered WC-Co base alloys at the room temperature and the composition of the binder phase, that is, the carbon content of the alloys, have been investigated. It was found that the properties were strongly affected by the binder phase composition, although any harmful phase was not formed in-the structures of alloys. On the other hand, researches on the subject for sintered WC-Ni.alloys have never been carried out and it is still vague whether Co is superior to Ni or not as the binder metal of cemented carbides.Therefore, studies on the properties of the WC-10%Ni alloy in relation to the composition of the binder phase were carried out. The results were compared with those already known for WC-10%Co alloy, to get an accurate knowledge on the superiority of Co or Ni as the binder metal. Specimens were vacuum-sintered at mostly 1450°C for lhr. The carbon content of alloys was closely controlled. Results obtained are summarized as follows.(1) Sintering temperature of WC-10%Ni alloy was higher by about 70°C than that of 10%Co alloy. This shows that the temperatures at which the liquid phase is formed, are in this case higher by about 70°C than corresponding temperatures of WC-10%Co two phase alloys. (2) The two phase range in WC-10%Ni alloy extended from about 5.77 to 6.06%C in WC and the width of the range corresponded to about 0.3%C (the values in WC-10%Co alloy are about 6.04-6.22%C and 0.15-0.18%C, respectively). Based on the former result, it is clear that the free carbon phase is formed more easily in Ni-binding alloy than the other. (3) The amount of W dissolved in the binder phase varied abruptly from about 10% to 31% according to the carbon content of the two phase alloys (the value in Co-binding alloy is in the range from 2-3% to 9.10%). (4) Properties such as density, hardness, transverse-rupture strength, magnetic saturation and resistance to acidic solution, etc. showed regular changes in the phase range. These changes were explained by the composition changes in the binder phase. The maximam strength of the alloy was obtained at about the highest carbon side of the range ; however, the value was inferior to that of the Co-binding alloy. The reason may be that the content of the W dissolved in the binder phase in Ni-binding alloy is much higher than that of the other. The alloy having carbon content of less than 5.95% was found to be non-magnetic. (5) Aging phenomena taken place during annealing at temperatures as low as 800°C were not observed in the Ni-binding alloy. (6) The rapid grain growth of WC was observed in the high carbon alloys. (7) From these results, Co was confirmed to be by far superior to Ni as the binder metal of cemented carbides, except for a few cases.

Properties of WC-TiC-10%Co(β-10%Co) Two Phase Alloys in Connection with Carbon Content of Alloys

The relation between the basic properties of typical WC-β-Co three phase alloys and the carbon content was already reported. In this report, the researches on the same subject have been carried out mainly on β-Co two phase alloys. The cobalt content in the alloys was mainly kept at 10wt%, and the titanium carbide content in carbides was 30%, 50% or 25%. The carbon content was strictly controlled. Samples were vacuum-sintered at 1430°C for 1 hr.Main results obtained were as follows ;(1) The lattice parameter of γ-phase varied with the increase of carbon content of alloys, from about 3.593A to 3.560A and from about 3.605A to 3.560A in 30% and 50% titanium carbide alloys, respectively. (2) The lattice parameter of γ-phase in 25% titanium carbide alloy (containing a small amount of WC phase) was between that of β-Co two phase alloy and that of typical WC-β-Co three phase alloy. (3) W dissolved much more than Ti.in the γ-phase in the low carbon alloys. (4) The lattice parameter of β-phase varied with the increase of carbon content of the alloys, from about 4.314A to 4.321A and from about 4.318A to 4.324A in 30%b and 50% titanium carbide alloys, respectively. (5) The change in carbon content of β-phase resulted in the extension of (β+γ) two phase range. Continued from (WC+β+γ) three phase range, the width of the range increased with the increase in the titanium carbide content. (6) Phenomena mentioned above could be explained by the Ti-W-C three phase diagram. (7) Other properties showed regular changes in the phase range.

炭素量の変化を考慮してのWC-10%Co合金の性質と粒度との関係

It has been reported that the composition of the binder-phase of two phase alloys changes remarkably from about 2∼3% to 9∼10%W due to a small change of their carbon content, so that the properties and the aging characteristics of cemented carbides are directly influenced by the composition. In this report, some properties of cemented carbides affected by the particle size are investigated in close consideration of the composition of the binder phase. The properties such as hardness, strength, magnetic saturation, coercive force and electrical resistivity of the alloys and the lattice parameter of binder phase, are measured.The results obtained may be summarized as follows. (1) The value of coercive force is not only dependent upon the particle size, but also upon the tungsten content of the binder phase. Therefore, the determination of the mean particle size by a coercive force method is erroneous. (2) The hardness and electrical resistivity decrease with increasing of the particle size and the carbon content. (3) The transverse-rupture strength shows a maximum under the condition that the mean particle size is about 2.0μ and the carbon content of WC is about 6.20% which is almost the maximum carbon content of the two-phase alloy. And as a condition to obtain a maximum strength, it is generally accepted in the two-phase alloy that the carbon content should be almost maximum, if the particle size is nearly equal to or less than about 2.0μ, but in the case of a fairly coarser particle size it should be almost minimum. (4) Both the lattice constant of the binder phase and the magnetic saturation of the alloy are not influenced by the particle size of WC, that was developed after sintering. Therefore, it is clear that the tungsten content in the solid binder phase has no relation to the particle size, provided that the carbon content of the alloy is invariable. (5) But the rate of precipitation of Co3W, when low carbon alloys are annealed at low temperatures, is sensitive to the particle size. A carbide structure of coarse and homogeneous particle size is desirable to stabilize the properties of low carbon alloys at a higher temperature.