Effects of Carbon Concentration Change on Growth of Compound Layer in Surface of Nitrided Steel

When steel is nitrided, a compound layer mainly composed of iron nitrides, ε-Fe2~3N and the γ’-Fe4N phase, is formed on the steel surface. It is an extremely important industrial issue to clarify factors governing the formation of the compound layer during nitriding and to establish unified views on the mechanism of compound layer formation. Therefore, in order to clarify the effect of change in carbon concentration on the growth of the ε phase and the γ’ phase in the compound layer on nitrided steel, we evaluated the change over time in the concentration of the alloy elements in the surface layer, and the phases of the compound layer on nitrided steels containing various amount of carbon in the matrix. The results were that the change over time in the carbon concentration in the compound layer was mainly responsible for the change over time in the phases of the compound layer. Furthermore, it was discovered that the change over time in the carbon concentration distribution occurred because both increasing of carbon from the matrix to the compound layer, and decreasing of carbon from the surface of compound layer to the atmosphere. That caused the gradient change of chemical potential of carbon in the through-thickness direction of compound layer, and the phases of the compound layer were changed with the treatment time.

Download Full-text

Effect of different compound layer and base material microstructures on microstrain and domain size of nitrided steel

Surface Engineering ◽

10.1179/sur.1998.14.6.481 ◽

1998 ◽

Vol 14 (6) ◽

pp. 481-488 ◽

Cited By ~ 10

Author(s):

T. Hirsch ◽

F. Hoffmann ◽

P. Mayr

Keyword(s):

Base Material ◽

Domain Size ◽

Compound Layer ◽

Nitrided Steel

Download Full-text

ABOUT HEAT CAPACITY OF TITANIUM CARBIDE TiCx

Alternative Energy and Ecology (ISJAEE) ◽

10.15518/isjaee.2019.01-03.056-066 ◽

2019 ◽

pp. 56-66

Author(s):

I. Khidirov ◽

V. V. Getmanskiy ◽

A. S. Parpiev ◽

Sh. A. Makhmudov

Keyword(s):

Heat Capacity ◽

High Temperature ◽

Titanium Carbide ◽

Temperature Dependence ◽

Carbon Concentration ◽

Room Temperature ◽

Thermodynamic Characteristics ◽

Liquid Nitrogen Temperature ◽

Analysis Data ◽

Thermal Excitation

This work relates to the field of thermophysical parameters of refractory interstitial alloys. The isochoric heat capacity of cubic titanium carbide TiCx has been calculated within the Debye approximation in the carbon concentration range x = 0.70–0.97 at room temperature (300 K) and at liquid nitrogen temperature (80 K) through the Debye temperature established on the basis of neutron diffraction analysis data. It has been found out that at room temperature with decrease of carbon concentration the heat capacity significantly increases from 29.40 J/mol·K to 34.20 J/mol·K, and at T = 80 K – from 3.08 J/mol·K to 8.20 J/mol·K. The work analyzes the literature data and gives the results of the evaluation of the high-temperature dependence of the heat capacity СV of the cubic titanium carbide TiC0.97 based on the data of neutron structural analysis. It has been proposed to amend in the Neumann–Kopp formula to describe the high-temperature dependence of the titanium carbide heat capacity. After the amendment, the Neumann–Kopp formula describes the results of well-known experiments on the high-temperature dependence of the heat capacity of the titanium carbide TiCx. The proposed formula takes into account the degree of thermal excitation (a quantized number) that increases in steps with increasing temperature.The results allow us to predict the thermodynamic characteristics of titanium carbide in the temperature range of 300–3000 K and can be useful for materials scientists.

Download Full-text

Corrosion of Welded Metal Structures of Mining Equipment

Revista de Chimie ◽

10.37358/rc.18.9.6576 ◽

2018 ◽

Vol 69 (9) ◽

pp. 2563-2566

Author(s):

Dan Dobrota

Keyword(s):

Carbon Concentration ◽

Welded Joints ◽

Construction Material ◽

Working Environment ◽

Mining Equipment ◽

Metal Structures ◽

Corrosion Phenomenon ◽

Welding Regime ◽

New Material ◽

Initial Research

Mining equipment made of welded metal structures is strongly affected by the corrosion phenomenon due to the working conditions. Initial research has shown that the corrosion phenomenon is most pronounced in the area of cross-welded joints and welded T-shaped joints. In the researches, there was made a chemical analysis of the welded construction material used respectively of the new material and it was observed a reduction in carbon concentration in the material used, but also a substantial increase in the sulfur concentration compared to the new material. The pronounced corrosion of the metallic structure is influenced by the chemical composition change because the sulfur is a grafitizing and weakening element, and the decrease in carbon concentration causes a decrease in corrosion resistance. Also, the pronounced corrosion is due to the action of sulfurous acid (H2SO3) and hydrogen sulfide (H2S), elements that are present in the working environment of welded constructions. In order to achieve a reduction in the corrosion phenomenon, it is very important that the welded joints are made using the optimal parameters of the welding regime so as to obtain metallographic structure with finer granulations.

Download Full-text

EFFECT OF PHOTOCHEMICAL TRANSFORMATION ON DISSOLVED ORGANIC CARBON CONCENTRATION AND BIOAVAILABILITY FROM WATERSHEDS WITH VARYING LANDCOVER

10.1130/abs/2018ne-311064 ◽

2018 ◽

Author(s):

Ashley R. Sanders ◽

◽

Andrew W. Vermilyea

Keyword(s):

Organic Carbon ◽

Dissolved Organic Carbon ◽

Carbon Concentration ◽

Photochemical Transformation ◽

Organic Carbon Concentration

Download Full-text

Similarity problems of the theory of unsteady concentration boundary layer

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19832751 ◽

1983 ◽

Vol 48 (10) ◽

pp. 2751-2766

Author(s):

Ondřej Wein ◽

N. D. Kovalevskaya

Keyword(s):

Boundary Layer ◽

Approximate Method ◽

Steady Flow ◽

Broad Class ◽

Concentration Boundary Layer ◽

Concentration Change ◽

Concentration Boundary ◽

Flow Problems

Using a new approximate method, transient course of the local and mean diffusion fluxes following a step concentration change on the wall has been obtained for a broad class of steady flow problems.

Download Full-text