Quasiternary system Fe-TiC-TiB2

Conclusions Fe-TiC-TiB₂ is a quasiternary system, i.e., a secondary system with respect to the quaternary full (primary) system Fe-C-B-Ti. The quasiternary system has a simple melting diagram with a ternary eutectic melting at a temperature of 1170°C. The structure of the eutectics in the alloys investigated is characterized by the formation of a metallic matrix. The hardness of the alloys in the as-cast condition substantially grows with rising titanium carbide ortitanium diboride concentration. The hardness of the TiC-TiB₂ eutectic is a minimum compared with that of noneutectic alloys of this quasibinary system.Translated from Poroshkovaya Metallurgiya, No. 12(204), pp. 60–64, December, 1979.     

Reactions in the system ZrC-ZrB2

Conclusions It is shown that in the system ZrC-ZrB₂ there is virtually no intersolubility of the components up to 2100°C, and it is only at a temperature of 2650°C that some dissolution of ZrB₂ (<2 wt.%) is observed. Using data yielded by x-ray diffraction and metallographic examinations and measurements of the initial melting temperatures of ZrC-ZrB₂ alloys and of the microhardness of their structural components, a constitution diagram has been constructed for the system under investigation. The diagram is of the eutectic type, with T_e=2660±40°C and a eutectic composition of 57 ZrB₂ and 43 mole% ZrC.Translated from Poroshkovaya Metallurgiya, No. 5 (149), pp. 61–64, May, 1975.     

Creep in the binary systems TiB2-TiC and ZrB2-ZrN

Conclusions It has been established that two-phase TiB₂-TiC and ZrB₂-ZrN alloys with approximately equal concentrations of their components exhibit the highest values of creep rate, which is linked with the manifestation of structural superplasticity. The maximum values of creep strain strongly depend on the inclusion size of the component phases.Translated from Poroshkovaya Metallurgiya, No. 8 (140), pp. 17–21, August, 1974.     

Partial phase relationships in Ir-Nb-Ni-Al and Ir-Nb-Pt-Al quaternary systems and mechanical properties of their alloys

Two quanternary systems, Ir-Nb-Ni-Al and Ir-Nb-Pt-Al, were successively investigated to assess their possible use in ultra-high-temperature applications. The phase relationships concentrated on the fcc/L1₂ two-phase region were primarily established, and the mechanical properties were studied. Ir-Nb-Ni-Al quaternary alloys around the Ir-rich or Ni-rich corners of the Ir-Nb-Ni-Al tetrahedron showed a coherent fcc/L1₂ two-phase structure, analogous to that of Ni-base superalloys; however, most of the alloys presented three or four phases with two types of L1₂ phases. Although these alloys showed a high compressive strength at high temperature, they exhibited a higher creep rate than Ir-base binary and ternary alloys. Another quanternary system, Ir-Nb-Pt-Al, showed promising results. Only an fcc/L1₂ two-phase structure was found in all the alloys investigated with compositions ranging from the Ir-rich side to the Pt-rich side, and the lattice misfit between the fcc and L1₂ phases was small. The high-temperature strength at 1200 °C of Ir-Nb-Pt-Al alloys was higher than that of Ir-Nb-Ni-Al alloys with the same Ir content (at. pct). Moreover, Ir-Nb-Pt-Al alloys exhibited excellent creep resistance at 1400 °C and 100 MPa. This article is based on a presentation made in the symposium entitled “Beyond Nickel-Base Superalloys,” which took place March 14–18, 2004, at the TMS Spring meeting in Charlotte, NC, under the auspices of the SMD-Corrosion and Environmental Effects Committee, the SMD-High Temperature Alloys Committee, the SMD-Mechanical Behavior of Materials Committee, and the SMD-Refractory Metals Committee.     

High-temperature friction of alloys of the TiNx-TiB2 system

Conclusions It has been established that the highest transverse rupture strength and wear resistance combined with the lowest coefficient of friction are shown by alloys of eutectic composition. In alloys of the TiN_0·9-TiB₂ system higher ductility during friction is exhibited by the boride phase, whose substructure experiences greater changes compared with the nitride phase. The greatest deformation during friction characterizes the phases in the TiN_0·73-TiB₂ alloy. The strengthening and strength loss processes at temperatures of 20–400°C are determined by the strength loss processes occurring in the boride phase, and those above 400°C, by the strengthening and strength loss processes taking place in the nitride phase.Translated from Poroshkovaya Metallurgiya, No. 2(242), pp. 70–76, February, 1983.     

Sinter-bonding of Cr3C2 to chromium carbide alloys

Conclusions The sinter-bonding of electrophoretically deposited Cr₃C₂ coatings to KKhN and KKhNF chromium carbide alloys is a result of liquid-phase reaction and of migration of the metallic phase from the basis materials to the carbide layers. The structure and properties of resultant coatings are determined by the sinter-bonding temperature and the composition of the basis material, but are not significantly affected by the latter's condition. Phosphorus-free chromium carbide alloys are preferable to KKhNF alloys as basis materials because they enable optimum properties in coatings to be obtained at a lower temperature.Translated from Poroshkovaya Metallurgiya, No. 9(261), pp. 52–56, September, 1984.     

Magnetic investigation of microstress in hard alloys

Conclusions The variation of microstress in Co-(Ti, W)C solid solutions and two-phase titanium-tungsten hard alloys of various compositions is essentially similar in character to that in the corresponding systems Co-WC and WC-Co. The level of microstress in the cobalt and carbide phases of two- and three-phase titanium hard alloys changes sharply as a function of alloy composition (cobalt and titanium carbide contents). The microstresses in the Co phase (tensile) and in the WC phase (compressive) do not change sign, while the microstress (Ti, W)C in the titanium phase does change sign, when the cobalt or titanium carbide content of the alloys is varied.The character of microstress variation in titanium-tungsten hard alloys depends also to a large extent on their structure — the presence of continuous carbide skeletons in low-cobalt alloys and of (Ti, W)C grain conglomerates in alloys of comparatively high cobalt content. The composition of the cementing phase and the presence of additional phases (graphite, ₁ phase, pores) can also be expected to constitute contributory fators.In the case of three-phase titanium-tungsten alloys, the most widely used hard-alloy tool materials, there is a correlation between the microstress in their cobalt phase and their transverse rupture strength, which could be utilized for the formulation of new grades of alloys of this type.Translated from Poroshkovaya Metallurgiya, No. 10(166), pp. 64–71, October, 1976.     

Electrical properties of high-temperature conducting powder MoSi2-SiC-Y2O3 materials

Conclusions We examined the concentration and temperature dependences of the specific electrical resistivity in the two- (MoSi₂-SiC) and three-phase (MoSi₂-SiC-Y₂O₃) systems in the temperature range 100–1800°C. In the two-phase system, the lowest TCR in heating to 1800°C was recorded for the materials with the mass content of SiC of 20–40%. The results show that the TCR of the two-phase materials of the MoSi₂-SiC system can be reduced by adding yttrium oxide to them.Translated from Poroshkovaya Metallurgiya, No. 6(306), pp. 83–85, June, 1988.     

Interaction of vanadium carbide with a nickel-molybdenum alloy

Melting and solidification temperatures for Ni-Mo alloys (the ratio of these elements is 3:1) containing 10% (by weight) of vanadium carbide are determined. Introduction of vanadium carbide into Ni-Mo alloy reduces the melting temperature by 20°C. The alloys consist of two phases: a solid solution based on nickel and a carbide component resembling needle-shaped inclusions of the eutectic type. Traces of eutectic are observed with 1% VC in a sample. Dissolution of vanadium in the Ni-Mo alloy mentioned does not exceed 1% (by weight). The presence of two phases and their approximate composition in the alloys are confirmed by x-ray diffraction analysis. The solid solution based on nickel contains molybdenum (10–20%) and vanadium (1–6%). The carbide component is a vanadium-containing phase based on molybdenum with a crystal lattice of the Mo₂C type.Scientific Research Institute of Refractory Metals and Hard Alloys. Moscow. Translated from Poroshkovaya Metallurgiya, Nos. 1–2, pp. 59–62, January–February, 1994.     

Examination of the physical properties of ZrC-W carbide-metallic alloys

Conclusions The heat conductivity of the two-phase alloys of ZrC-W system increases with an increase of the tungsten content and with increase in temperature. This is caused by the electron contribution to the heat conductivity of the crbide phase.The electrical resistance of these alloys decreases with increase in tungsten content and increases with increase in temperature. At a mass constant of ZrC > 25% the temperature dependence of the electrical resistance of the alloys is nonlinear as a result of slight overlapping of the valency band by the conduction band in the carbide phase.The mean coefficient of thermal expansion ZrC-75% (wt.) W alloy increases with increase in temperature from 5.5·10^–6 in the range 300–600 to 7.05·10^–6 K^–1 in the range 300–2300°K.The spectral emission factor =0.65 mm of the ZrC-W alloys increases with an increase of the zirconium carbide content. With increase in temperature decreases for tungsten, zirconium alloy, and alloys with a mass content of W < 40%. For the alloys with a tungsten content of 45–75% depends only slightly on temperature. This can be explained by the presence of tungsten carbides in the subsurface layer. The critical wavelength of these carbides (_X=500–600 nm) is close to the wavelength in pyrometric measurements.The fracture tensile stress of the specimens of the alloys with a mass constant of tungsten of 75% increases with increase in temperature as a result of utilization of a certain ductility margin of the brittle material.Translated from Poroshkovaya Metallurgiya, No. 6(330), pp. 93–100, June, 1990.     

Phase diagram of the Co-VC-NbC system

Conclusions The eutectic in the Co-VC system corresponds to the composition with 14% VC and a temperature of 1340 ± 20°C and the maximum solubility of vanadium carbide in cobalt is 6%. The Co-VC section is not a quasibinary section of the Co-V-C phase diagram.The eutectic in the Co-NbC system melts at 1360°C and contains 11–12% NbC.The as-cast alloys of the Co-VC-NbC system are in the metastable two-phase condition and the only carbide phase is a carbide of complex composition which is a three-component solid solution of vanadium and niobium monocarbides.The fusibility diagram of the equilibrium phase diagram of the Co-VC-NbC system is characterized by the four-phase eutectic equilibrium L Co + VC + NbC with the point of the ternary eutectic at 1330 ± 20°C and a composition of 11% VC, 4% NbC, and 85% Co. The Co-VC-NbC equilibrium phase diagram does not contain ternary compounds and the equilibrium phases are cobalt- and vanadium- and niobium carbide-base solid solutions. The total volume share of the carbide constituents of the ternary eutectic somewhat exceeds the share of carbide phases in the boundary eutectics Co-VC and Co-NbC.The total solubility of the carbides in cobalt does not exceed 2–3%.Translated from Poroshkovaya Metallurgiya. No. 3(315), pp. 80–87, March, 1989.     

Phase equilibria in the systems vanadium-chromium-carbon,niobium-chromium-carbon,and tantalum-chromium-carbon

Conclusions The systems V-Cr-C, Nb-Cr-C, and Ta-Cr-C were investigated by x-ray diffraction and metallographic techniques. The phase equilibria in the system V-Cr-C at 1000°C and the existence of a compound of the approximate composition VCr₂C₂ were established. The solid solubility of chromium in VC is 30 at.% and in V₂C 32–33 at.%. The phase equilibria in the systems Nb-Cr-C and Ta-Cr-C at 1050 and 1000°C were also determined. The ternary carbide Nb₃Cr₃C was not detected.Translated from Poroshkovaya Metallurgiya, No. 3 (63), pp. 42–48, March, 1968.     

Creep of Al2O3-AlN and Y2O3-AlN ceramics

Conclusions An investigation into the creep of Al₂O₃-AlN and Y₂O₃-AlN ceramics has demostrated that the addition of 20–80% AlN reduces the creep rate of Al₂O₃. In the system Y₂O₃-AlN the existence of a creep rate maximum has been discovered, which may be a manifestation of structural superplasticity.Translated from Poroshkovaya Metallurgiya, No. 2(158), pp. 76–82, February, 1976.The authors wish to thank Prof. R. A. Andrievskii for his interest in this work.     

Creep Behaviors of Two Near-Eutectic Al-Si-Cu-Mn Heat-Resistant Alloys Containing Dendritic Mn-Rich Primary Phase or Modified Star-Like Cr-Mn-Rich Primary Phase

In this study, the creep responses of two near-eutectic Al-Si-Cu-Mn alloys, Al-12wt pctSi-4 pctCu-1.2wt pctMn alloy (Alloy-1, containing dendritic Mn-rich primary phase) and Al-12wt pctSi-4 pctCu-2wt pctMn-1wt pctCr alloy (Alloy-2, containing star-like Cr-Mn rich primary phase), were investigated from 448 K to 523 K at 40 to 70 MPa applied stress. Results show that with 100 hours of exposure at 448 K/40 to 70 MPa, true steady-state creep was not attained. However, at 473 to 523 K/40 to 70 MPa, both the alloys showed a fixed creep rate establishing steady-state creep. The creep curves of the studied alloys illustrate that Alloy-1 exhibits lower creep rates and less creep strains than Alloy-2 in each combination of temperature and applied stress. Considering the creep rates and total creep strains after 100 hours of exposure, Alloy-1 possesses much better creep resistance than Alloy-2, even though the high-temperature strength of Alloy-2 is higher than that of Alloy-1 at 448 K and 523 K. Higher strength at high temperatures does not mean high creep resistance at high temperatures. At low to moderately high temperatures (0.48 to 0.53 T_m where T_m is the equilibrium melting point of pure Al in K) and applied stress of 40 to 70 MPa, the creep mechanisms in Alloy-1 and Alloy-2 are similar and diffusion is the rate-controlling process.

     

Compressive creep properties of Ir-base refractory superalloys

Ir-base alloys with the fcc and L1₂-Ir₃X (X = Nb, Zr) two-phase structure have been developed as next-generation high-temperature materials. The compressive creep behavior of Ir-Nb and Ir-Zr alloys was investigated at 2073 K under 137 MPa. The effect of addition of the third element, Zr, on the creep behavior of an Ir-Nb alloy was also investigated at 2073 K for 137 MPa. The creep rate became two orders lower by addition of a small amount of Zr. The lattice misfit change between the fcc and L1₂ two phase by addition of Zr and the deformation structure in binary and ternary alloys after a creep test were also investigated. The creep behavior is discussed in terms of the lattice misfit, precipitate shape, and their distribution. This article is based on a presentation made in the symposium entitled “Beyond Nickel-Base Superalloys,” which took place March 14–18, 2004, at the TMS Spring meeting in Charlotte, NC, under the auspices of the SMD-Corrosion and Environmental Effects Committee, the SMD-High Temperature Alloys Committee, the SMD-Mechanical Behavior of Materials Committee, and the SMD-Refractory Metals Committee.     

Microindentation and Macroindentation of Titanium Silicon Carbide Ti3SiC2

We have studied the behavior of titanium silicon carbide Ti₃SiC₂ in different structural states (one-phase and two-phase, compacted, porous) during microindentation (load up to P = 0.9 N) at room temperature with automatic recording of the loading, holding, and unloading diagrams. We used scanning electron microscopy to study the microstructure around the macrohardness indentations (P = 10–200 N). The results obtained are compared with corresponding data for a number of metallic and ceramic materials. On the P - h loading diagrams (h is the penetration depth), we observe plateaus which are the result of microfracture of the material under the indentor. This reflects the characteristics of titanium silicon carbide: when it is loaded, intergrain and intragrain microcleavage occurs. The plasticity (or pseudoplasticity) of the material can be characterized using the relative work dissipated in the deformation, i.e., expended for irreversible deformation, which can be determined during microindentation: λ _p = A _p /A.__________Translated from Poroshkovaya Metallurgiya, Nos. 3–4(442), pp. 93–105, March–April, 2005.     

Reactions in the VC0.88-VB2 system

Conclusions A constitution diagram of the VC_0.88-VB₂ system has been constructed on the basis of data yielded by metallographic examinations, x-ray diffraction and chemical analyses, melting point determinations on alloys, and microhardness measurements on their individual phases. The diagram is of the eutectic type, with T_eut = 2120 ± 20°C, the composition of the eutectic being 54 mole % VC + 46 mole % VB₂. Vanadium carbide dissolves up to 10 wt. % of VB₂ at T_eut, the solubility of VC in VB₂ being negligible.Translated from Poroshkovaya Metallurgiya, No. 2(230), pp. 49–51, February, 1982.     

Deformation and fracture behavior of a directionally solidified β/γ′ Ni-30 At. pct Al alloy

The effect of a ductile γ′-Ni₃Al phase on the room-temperature ductility, temperature-dependent yield strength, and creep resistance of β-NiAl was investigated. Room-temperature tensile ductility of up to 9 pct was observed in directionally solidified β/γ′ Ni-30 at. pct Al alloys, whereas the ductility of directionally solidified (DS), single-phase [001] β-NiAl was negligible. The enhancement in ductility was attributed to a combination of slip transfer from the ductile γ′ to the brittle β phase and extrinsic toughening mechanisms such as crack blunting, deflection, and bridging. As in single-phase Ni₃Al, the temperature-dependent yield strength of these two-phase alloys increased with temperature with a peak at approximately 850 K. The creep strength of the β/γ′ alloys in the temperature range 1000 to 1200 K was found to be comparable to that of monolithic β-NiAl. A creep strengthening phase needs to be incorporated in the β/γ′ microstructure to enhance the elevated temperature mechanical properties.     

Cyclic strength of hard metals

Conclusions The fatigue limit of the titanium carbide and tungsten carbide alloys investigated on a basis of 5·10⁸ cycles lies in the range (20–30)·10⁷ Pa, and is thus comparable with the endurance of type ShKh high-carbon (1% C-Mn-Si-Cr) ball-bearing steels. The strength and character of fracture of the hard metals are determined by the properties and structural state of their phase constituents. The highest strength is exhibited by tungsten carbide and titanium carbide alloys with evenly distributed equal-sized carbide grains. The character of fracture of the hard metals varies depending on their method of loading, from brittle in static loading to tough-and-brittle in cyclic loading. On time bases not exceeding 10⁶ cycles titanium carbidehard metals are comparable in fatigue resistance to the standard tungsten-containing hard metals.Translated from Poroshkovaya Metallurgiya, No. 9(273), pp. 67–71, September, 1985.