A. A. Bondar

Phase equilibria in the Cr-Ni-C system and their use for developing physicochemical principles for design of hard alloys based on chromium carbide

The Cr—Ni—C phase diagram at the melting point was plotted by a combination of procedures (metallography, x-ray, microprobe, differential thermal analysis, Pirani—Alterthum method, etc.). A general feature of this system is the existence of equilibria between the nickel-based phase and all the other phases. The temperature of the quasibinary (Ni)+(Cr7C3) eutectic was determined to be 1324±6°C. Based on both the phase diagram of the Cr—Ni—C system and the bending strength and Rockwell hardness of the alloys, the optimal composition of the initial carbide ingredient for production of hard alloys based on Cr3C2 with nickel—phosphorus binder was estimated as 13.0–13.3 at.%, substoichiometric with respect to Cr3C2.

Metallochemistry of chromium in ternary systems formed by chromium with d-metals and carbon ☆

Abstract The results of the experimental investigation of phase equilibria at solidus temperatures of the Cr–Nb(Ta,Re)–C systems are given. They add much to the information on the Cr–dM–C systems. Certain regularities have been revealed for the phase diagram constitution, particularly detailed for those formed with high valence d-metals and applied as a basis for prediction of the Cr–Tc–C phase diagram at high temperatures yet unstudied experimentally.

Phase diagram of the Cr-Mo-C system 1. Phase equilibria in the area of crystallization of alloys of the Mo-Mo2C-Cr7C3-C partial system

This article presents the results of an investigation of alloys of the Cr-Mo-C system at temperatures of existence of solid phases with the liquid one and in the subsolidus area, which made it possible to construct the high temperature area of the phase diagram of the Mo-Mo/sub 2/C-Cr/sub 7/C/sub 3/-Cr partial system. The phase transformations were investigated by differential thermal analysis on an instrument with a W-VR-20 string thermocouple in high-purity helium. The specimens were placed in a crucible of Y/sub 2/O/sub 3/, HfO/sub 2/, or Sc/sub 2/O/sub 3/. The calibration was done using Al, Au, Pd, Pt, and Rh as reference points (auxiliary ones carbonyl iron and + Mo/sub 2/C eutectic). To decrease and take into consideration the error in temperature measurement of the nonvariant equilibria the tests were made several times. The error in reproduction of the temperature scale was determined with the use of regression analysis.

The Cr−Re phase diagram

The phase diagram for the Cr−Re system has been derived from published data in conjunction with measurements on alloys cast and annealed at subsolidus temperatures (XRD, metallography, microprobe analysis, and measurement of the temperature for the onset of melting by the Pirani—Alterthum method). The phase equilibria at solidus temperatures have been determined from studies on alloys annealed at those temperatures. Phase homogeneity regions on the solidus have been identified: for (Cr) up to 43 at.% Re, for the σ phase −50–72 at.%Re, and for (Re) up to 17 at.%Cr; temperatures have also been determined for the invariant equilibria L+σ ⇆ (Cr) at 2150±15°C and L+(Re)⇆σ at 2335±15°C.

Rhenium solid solution in the CrReC ternary system at solidus temperature

Abstract The CrReC system was investigated by metallography, X-ray diffraction, microprobe, differential thermal analyses and Pirani-Alterthum techniques and the solidus surface was constructed. The combined maximum solubility of chromium and carbon in rhenium at solidus temperature (1700°C) was found to be 53 and 36 at.%, respectively. The lattice parameters at this composition, (Cr 0.82 Re 0.18 ) 2 C carbide, are a = 0.2833(1) and c = 0.4443(6) nm.

The (Cr) + (NbC) quasibinary eutectic in the Cr - Nb - C system

An experimental investigation of the Cr - Nb - C alloys has shown that in the (Cr) + (NbC) two-phase region there are the fold with maximal solidus temperature and the saddle point (Cr79.5Nb12.2C8.3) on the liquidus surface, relating to Lc ⇔ (Cr) + (NbC) invariant equilibrium at ≥1640°C.

Structure and Properties of Iron–High-Carbon Ferrochrome Powder Composites

The physical and process properties of ferrochrome powder produced by grinding of lump high-carbon ferrochrome FKh800 are examined. It is found that the ferrochrome is pulverized sufficiently well, and its physical and process properties allow its use to make wear-resistant powder materials. The effect of ferrochrome content on the structure and properties of materials sintered in vacuum from iron powder compacts and powdered FKh800 is studied. The materials containing 30 wt.% FKh800 are found to have high density, bending strength, hardness, and resistance to abrasive wear.

Titanium-Boride Eutectic Materials: Phase Equilibria and Constitution of Alloys in the Ti-rich Portion of the Ti-V-B System

Phase equilibria and constitution of alloys were experimentally investigated in the Ti-TiB-(Ti_o 5V_o 5)BTi_4oV-6o region using metallography (optical microscopy and SEM/EPMA), differential thermal analysis (DTA), and X-ray diffraction (XRD). The phase diagram in the • melting (solidification) temperature range has been constructed as solidus and liquidus surfaces projections and a vertical section at 9 at.% B. The V alloying was found to decrease melting temperatures from 1500 °C for the binary (Ti) + TiB eutectic to 1430 °C for the ternary invariant equilibrium Le <-» (Tio.63Vo.37) + (Ti0.74V0 26)B and then to increase them. At that, the composition of (ßTi,V) + (Ti,V)B monovariant eutectic becomes richer in boron, from 7.07.5 at.% Β in the Ti-B binary to about 8.5 at.% Β at 40 at.% V. The V contents in metal and boride phases after partition are comparable. Vanadium sharply decreases the α <-> β transition temperature, so that at ~10 to -15 at.% V as-cast arc melted alloys are multiphase and at -20 at.% V practically completed ß-stabilization is observed.

Melting Diagram for the Cr ― Nb ― C System in the (Cr) ― (Nb) ― ― (NbC) Region

It is shown from experimental tests on alloys in the Cr ― Nb ― C system in the region of the (Cr) ― (Nb) ― (NbC) subsystem at the melting (crystallization) temperatures that there are two nonvariant four-phase equilibria of congruent type: LE ↔ (Nb) + (Nb2C) + (NbCr2) at 1660°C and LE ↔ (NbC) + (Cr) + (NbCr2) at 1620°C; there is also one nonvariant four-phase equilibrium of incongruent transition type LU + (Nb2C) ↔ (NbC) + (NbCr2) at 1680°C; and two nonvariant three-phase equilibria of congruent type: Le ↔ (NbC) + (NbCr2) at 1696°C and Le ↔ (NbC) + (Cr) at 1640°C. A projection of the liquidus surface has been constructed together with the melting diagram for the system in the stated composition region.

Mixing Enthalpies of Melts and Thermodynamic Assessment of the Cu–Fe–Cr System

The mixing enthalpies of ternary liquid alloys in the Cu–Fe–Co system have been studied by calorimetric method at 1873 K and xCr = 0–0.45. The phase transformations in the Cu–Fe–Cr system have been examined using methods of physicochemical analysis. The thermodynamic assessment of the ternary system has been carried out in the framework of the CALPHAD method. The set of self-consistent parameters for thermodynamic models of the phases has been obtained taking into account experimental data of the present work and information on phase transformations. The isothermal and vertical sections of the phase diagram, liquidus and solidus surfaces, as well as metastable miscibility gaps of supercooled liquid alloys have been calculated. The degrees of supercooling for metastable liquid phase immiscibility have been assessed. The composition ranges for the formation of alloys with special structures have been predicted. The temperature–composition ranges for the formation of supersaturated solid solutions during liquid quenching have been evaluated.