Bulk Cementite Research Articles

Hydrogen Effects on Fracture Resistances of Bulk Cementite Evaluated by <i>in-situ</i> Microbending Test during Cathodic Hydrogen Charging

Hydrogen Effects on Fracture Resistances of Bulk Cementite Evaluated by <i>in-situ</i> Microbending Test during Cathodic Hydrogen Charging

Deformation Texture of Bulk Cementite Investigated by Neutron Diffraction

Understanding the deformation mechanism of cementite such as on a slip plane is important with regard to revealing and improving the mechanical property of steels. However, the deformation behavior of cementite has not been well investigated because of the difficulty of sample preparation given the single phase structure of cementite. In this study, by fabricating bulk single phase cementite samples using the method developed by the authors, the deformation texture formed by uniaxial compression was investigated using both electron back scatter diffraction and neutron diffraction. The fabricated sample had a random texture before the compression. After applying a compressive strain of 0.5 at 833 K, (010) fiber texture was formed along the compressive axis. It has been suggested from this trend that the primary slip plane of cementite is (010).

Hydrogen Permeation Property of Bulk Cementite

This study investigated the hydrogen permeation property of cementite by fabricating bulk cementite sample using the process combining the mechanical ball milling and subsequent pulse current sintering. The bulk cementite sample having a 96 vol% of cementite was successfully fabricated. The prepared bulk cementite showed no signal of hydrogen permeation during the 3.5 day of electrochemical hydrogen permeation test. The morphology of blister formed in the sample indicated that diffusion coefficient of hydrogen in cementite is very small.

Effect of interaction between cementite and pearlite on two-body abrasive wear behaviors in white cast iron

The wear interaction of cementite and pearlite in the white cast iron (WCI) was investigated using the two-body abrasive wear test under contact loads of 20, 35, and 50 N. The wear behavior, wear surface morphology, sub-surface structure, and wear resistance were evaluated using X-ray diffraction, microhardness testing, and nano-indentation. The results indicated that when the Cr content was increased from 0 to 4 wt%, there was a significant increase in the microhardness (H) and elasticity modulus (E) of the cementite. This yielded a 15.91%- and 23.6%-reduction in the degree of wear resistance and surface roughness, respectively. Moreover, no spalling and breaking of cementite was observed with increasing Cr content during the wear process, indicating improved wear resistance of the bulk cementite. In addition, the hard phase (cementite) and tough matrix (pearlite) composite structure exhibited a good protective and supporting effect. Thus, it was concluded that the interaction mechanism of the wear phase contributed to the reduction of the wear weight loss of the composite during the wear process. The contribution of the interaction between the hard wear-resistant phase and the tough phase in WCI to the wear resistance decreased with increasing hardness of the pearlite matrix.

Ultrasonic study on the change in elastic properties of cementite with temperature and Mn content using nearly full density polycrystalline bulk samples

The elastic properties of cementite were studied using a laser-ultrasonic technique. The temperature dependence and effect of Mn alloying were investigated using nearly full density polycrystalline bulk cementite samples. The Young’s modulus (E), shear modulus (G), bulk modulus (B), and Poisson’s ratio (ν) were obtained from the measured longitudinal and shear velocities (VL and VS, respectively). The elastic properties of cementite changed substantially with the temperature, especially around its Curie temperature (TC). The change in longitudinal velocity around Curie temperature was larger than the change in shear velocity. Around Curie temperature, a small decrease was observed in Young’s modulus and shear modulus and sharp minima were observed in bulk modulus and Poisson’s ratio. Mn addition to cementite increased the sound velocity and elastic stiffness and decreased Curie temperature. The present study revealed the temperature dependence of the elastic constants of cementite across Curie temperature for the first time.

Effects of Chromium Addition on Preparation and Properties of Bulk Cementite

Bulk cementites with the Cr contents of 0, 3. 01, 6. 03, 8. 22, and 11. 51 mass% were prepared by mechanical alloying (MA) and spark plasma sintering (SPS). The results indicated that when the Cr content was low (3. 01 mass%), the phases were composed of cementite with a small amount of α-Fe at a sintering temperature of 1 173 K, but the microstructure became single-phase alloyed cementite as the Cr content was further increased. It showed that microaddition of Cr was beneficial for promoting the formation of cementite. Furthermore, the mechanical performance of cementite can be greatly affected by the variation of Cr content. The hardness, elastic modulus and elastic recovery presented a remarkably increasing tendency with the addition of Cr, and the maximum micro-hardness and elastic modulus values reached 1 070. 74 HV and 199. 32 GPa, respectively, which were similar to the precipitation phase (cementite) obtained by melting and casting techniques. Moreover, when the Cr content was below 11. 51 mass%, the crystal structure of Fe3C-type cementite would not change with increasing the Cr content. A Cr atom replaced an Fe atom in the lattice of the cementite, and voids appeared when Cr was doped into the cementite at content of about 11.51 mass%, causing the relative density to decrease.

Two-body abrasion resistance of cementite containing different chromium concentrations

Abstract

Three-Body Abrasive Wear Behavior of Cementite with Different Chromium Concentrations

The abrasion-resistant properties of white cast iron, which is used as a wear-resistant material in many industrial applications, are affected by cementite properties. Hence, it is important to obtain an understanding of the mechanical properties and abrasive behavior of single-phase cementite. In this article, bulk cementite samples with 0, 3.01, 6.03, 8.22 and 9.76 wt% chromium were prepared using mechanical alloying and spark plasma sintering. Sample phase composition and mechanical properties were determined by X-ray diffractometry, microhardness testing and nano-indentation. When the chromium content was >6.03 wt%, bulk single-phase cementite was produced. The elastic modulus, elastic recovery and hardness increased with chromium content. When the chromium content was 9.76 wt%, the maximum microhardness was 1070.74 HV (Vickers hardness) and the maximum elastic modulus was 199.32 GPa. The cementite wear behavior was investigated using a three-body abrasive wear tester. Cementite with higher chromium content had a lower wear mass loss under a 3 kg load, which indicates that bulk cementite has an improved wear resistance. Short- and long-range plowing and chipping pits existed on the worn surface. Because a high-/low-chromium cementite composite structure was formed, this resulted in a significant decrease in worn surface roughness and chipping pit depth.

Two-body abrasive wear property of cementite

The abrasive wear property of single-phase cementite and cementite–iron composite, processed by mechanical alloying and spark plasma sintering, were investigated using a pin-abrasion test on fixed alumina abrasive grains. Single-phase cementite and cementite–iron composite had good wear resistances at applied pressures lower than 0.15 MPa. However, at applied pressures higher than 0.31 MPa, steels having a cementite volume fraction higher than 75% were intensely worn. In the former case, the wear mode of bulk cementite was ductile, and flow-type chips were observed on the worn surface. In the latter case, the wear mode was brittle, and brittle fracture chips were observed on the worn surface.

High temperature deformation behavior of bulk cementite produced by mechanical alloying and spark plasma sintering

Abstract Using the bulk cementite samples produced by mechanical alloying and spark plasma sintering technique, high temperature deformation behaviors of cementite were studied. To avoid decomposition at high temperature, 5 at.% Mn alloyed cementite ((Fe 0.95 Mn 0.05 ) 3 C) was mostly used. Brittle fracture was observed in the bulk cementite when deformed at a high strain rate at elevated temperatures (studied up to 1273 K). However, compression strain (this true strain larger than 2) was observed at around A 1 temperature (1000 K) at stresses in the range of 100–150 MPa. Specimens were deformed without cracks and without change in hardness. After this superplastic flow, grains are slightly elongated and grain growth was observed. It was demonstrated that the bulk cementite sheets can be deformed cooperatively with low carbon steel sheets and fine layered cementite/low carbon steel laminates could be fabricated by superplastic deformation. As a possible deformation mechanism of lamellae cementite in pearlite, grain boundary sliding was proposed.

Mechanical Properties of Cementite and Fabrication of Artificial Pearlite

The deformation behavior of cementite was studied using eutectoid steels with pearlitic and spheroidite structures and fine grained bulk cementite prepared by sintering the mechanically alloyed powders. Cementite lamellae in deformed pearlite exhibited inhomogeneous slip, thinning by deck-of-cards slip, homogeneous bending, fragmentation, cleavage fracture and cracking by shear bands. Complete dissolution of cementite lamellae and spheroidal cementite was also observed in specimens deformed at high strain rates. The polycrystalline bulk cementite is brittle and fractures within elastic limit when deformed below 573 K. However, large plastic deformation was observed when compressed at high temperatures (over 773 K) and low strain rates (10 -5 ~ 10 -3 s -1 ). The artificial pearlite was successfully fabricated by hot compression starting from the

Characterization of Bulk Cementite Produced by Mechanical Alloying and Spark Plasma Sintering

Characterization of Bulk Cementite Produced by Mechanical Alloying and Spark Plasma Sintering

Characterization of Alloyed Cementite Produced by Mechanical Alloying and Spark Plasma Sintering

Using the bulk cementite (Fe3C, θ) fabricated by mechanical alloying (MA) and spark plasma sintering (SPS), the mechanical properties of cementite such as Young's modulus, hardness and compression strength were measured. The abnormal decrease in Young's modulus and the abnormal increase in hardness with a decrease of temperature were observed at around the Curie temperature. It has been found that the hardness and Young's modulus of the alloyed cementite increased in the order of V, Cr, Mn and Mo. At elevated temperatures, cementite could deform in compression superplastically to large strain without cracks. Multilayers of cementite and ferrite with the layer thickness less than 100 µm could be fabricated by compression at elevated temperatures and this indicated a cooperative deformation of these two phases.

Production of bulk cementite and its characterization

Production of bulk cementite and its characterization

Influence of alloy additions on production and properties of bulk cementite

Influence of alloy additions on production and properties of bulk cementite

Ferromagnetic Domain Structures in Cementite

By means of transmission electron microscopy, ferromagnetic domain structures have been studied in thin cementite (Fe3C) particles embedded in a ferrite matrix. In general, the domain structure was found to consist of parallel strips alternately magnetized along the positive and negative direction of the easy axis of magnetization [001]. By means of selected-area electron diffraction the orientation of the cementite particles relative to the foil surface was determined. The domain walls lie in the (100) plane of the cementite lattice, and the width of the domains, as a function of angle between easy axis and normal to foil, agrees very well with the model of Malek and Kambersky. At the cementite-ferrite interface domains of closure frequently occurred in the ferrite, but were never found in the cementite. The width of the (Bloch) domain walls is roughly 100 Å, in reasonable agreement with the theoretical width computed for bulk cementite.