Iron-carbon System Research Articles

Effect of Interstitial Atoms on a Lattice-vacancy Diffusional Process

AN investigation has been made of the mechanism of diffusion of chromium into iron–carbon systems over the temperature range 950°–1,265° C. At temperatures above 825° C, the diffusional mechanism of chromium into iron is complicated by a change in crystal structure from a body-centred cubic lattice (α-phase) to a face-centred lattice (γ-phase). At low concentrations of carbon, a lattice-vacancy diffusional mechanism has been postulated, and a moving boundary model set up to represent this condition1. The results have confirmed that at concentrations of carbon of less than 0.16 per cent only lattice-vacancy diffusion was effective. At concentrations of carbon above this, the interstitial atoms hinder diffusion.

Correlation between the cold-work peak and the Snoek peak in the iron-nitrogen and iron-carbon systems

Correlation between the cold-work peak and the Snoek peak in the iron-nitrogen and iron-carbon systems

Some Reactions in the Iron–Carbon System: Application to the Tempering of Martensite

Some Reactions in the Iron–Carbon System: Application to the Tempering of Martensite

Binary and ternary interstitial alloys III. The iron-carbon system: the characterization of a new iron carbide

Cementite and iron percarbide are conveniently prepared by the methods described in the previous paper (part II). Iron percarbide has a narrow range of composition near 31 atomic % carbon and is identical with a carbide, assumed to be Fe 2 C, which was previously obtained by Hägg (1934). The iron percarbide unit cell is probably either orthorhombic, with dimensions a, 9.04(3); b = √3.a, 15.66(3); c, 7.92(1) kX, or hexagonal, with dimensions a' = 2a, 18.08(6); c' = c, 7.92(1) kX. There two possible units of structure are simply related, the volume of the latter being twice that of the former. The orthorhombic unit cell contains approximately 80 iron atoms, and the empirical formula for the carbide is Fe 20 C 9 . Although the existence of a carbide Fe 2 C is not disproved, it is unlikely that it has been prepared in this or any previous work. The cementite is identical with specimens formed below 700° C in steel and obtained by the action of carbon monoxide on ferric oxide. Both iron carbides are metastable. Iron percarbide decomposes giving cementite and carbon, and cementite breaks down less rapidly to give α iron and carbon.

A New Carbide in Chromium Steels

IN the course of X-ray investigations on the carbides formed in chromium and tungsten steels, a phase was encountered of a crystal structure identical with that of austenite, which at first it was thought to be. In fact, it proved to be a true carbide of iron and chromium. Its carbon content of 9·4 weight per cent carbon is similar to that in Cr7C3 (9·1 per cent C), compared with the maximum carbon solubility in austenite of only 1·7 per cent (at the eutectic in the iron–carbon system, chromium only decreasing this value). The carbides known in plain chromium steels since Westgren‘s1 early researches are (Cr,Fe)23C6, (Fe,Cr)3C and (Cr,Fe)7C3, all of which, as well as the present one, I found it possible to produce in the same steel by different heat-treatments. The carbide is believed to be of interest for its own sake, but also for more fundamental reasons given below.

Thermodynamics applied to the iron-carbon system

Thermodynamics applied to the iron-carbon system

A thermodynamic study of the iron-carbon system in the solid and liquid states.—II

The first page of this article is displayed as the abstract.

A thermodynamic study of the iron-carbon system in the solid and liquid states (I.)

A thermodynamic study of the iron-carbon system in the solid and liquid states (I.)

Preparation and properties of pure iron alloys: III. The effect of manganese on the structure of alloys of the iron-carbon system

Physical dependencies which connect crack resistance, K1c, with the effective and inner components of the yield stress, deforming stress and Brinell hardness HB of iron-carbon body-centred cubic (bcc) alloys such as pressure vessel and pipe steels, and spheroidal graphite cast irons, are discussed. The existence of a linear relationship between K1c and the parameter k1c/HB is demonstrated. An analogous correlation for impact strength KCV (Charpy test)-KCV/HB in low and transitional temperature zones is found. A practical procedure for prediction of crack resistance and impact strength within a wide temperature (T) range using the HB-T dependence and the values of K1c or KCV at T = 77 K is developed. Its possible variants are also described and discussed.

Preparation and properties of pure iron alloys: III. Effect of manganese on the structure of alloys of the iron-carbon system

Preparation and properties of pure iron alloys: III. Effect of manganese on the structure of alloys of the iron-carbon system

The chemical physics involved in the precipitation of free carbon from the alloys of the iron-carbon system

As a result of recent research it is held that the iron-carbon alloys must be considered as an iron-iron carbide system as indicated in the accompanying diagram; the author is satisfied that the double diagram based on the assumption of a metastable and a stable equilibrium is inaccurate, since, in the liquid or the solid state, that carbon which is in solution is contained in solution as carbide. The experiments to be described afford evidence that the carbide must separate out from the solution before free carbon can appear, and that it is only the structurally free carbide that can dissociate; free carbon will not separate from the solid solution.

Societies and Academies

Societies and Academies

Equilibrium of iron-carbon systems

Equilibrium of iron-carbon systems