Hypereutectic High Chromium Cast Iron Research Articles

Effects of Heat Treatment and Erosion Particle Size on Erosion Resistance of a Hypereutectic High-Chromium Cast Iron

This research addresses the erosive resistance of a hypereutectic high-chromium cast iron subjected to solid particle erosion. The study stems from a specific application of high-chromium cast iron, i.e., the critical surfaces of large industrial fans operating in a cement clinker grinding plant where such damage is a limiting factor for the components’ lifespan. A dedicated experimental investigation on the impact of substrate microstructure and erodent particle size on erosion resistance was set. The experimental campaign, conducted on a dedicated test bench per the ASTM G76 standard, comprised the analysis of the as-received, tempered, and destabilized conditions for the cast iron. From a preliminary image analysis of the microstructural features, two diameters of the erodent powder for the erosion tests were defined. The observed erosion rate decreased with the increase in the mean particle diameter of the erodent, indicating more severe erosive conditions for smaller particles. From the analysis of the worn surfaces, it was possible to highlight the involved mechanisms concerning the considered test combinations. For the as-received condition, the erosion rate with the larger mean particle diameter of the erodent decreased three times compared to the smaller one. For the heat-treated conditions, the erosion rate was halved with the larger mean particle diameter of the erodent. The proposed analysis, intended to acquire more insight into the limiting factor for the components’ lifespan for erosive wear damage, proved that erosion resistance is not dependent on the material’s hardness. The contribution of the mean particle diameter of the erodent is predominant compared to the substrate conditions.

Microstructure and properties of hypereutectic high chromium cast iron containing nitrogen

This article investigates the effect of N content on the microstructure, mechanical properties and wear resistance of hypereutectic high chromium cast iron (HHCCI). With the increase of N content, the primary carbides are obviously refined, the austenite content increases, and the dispersed granular Cr2N precipitates. After quenching at 1000 °C, secondary carbides are precipitated from the matrix, the matrix transforms into martensite + retained austenite. With the increase of N content, the corrosion resistance of HHCCI increases, and 0.3 wt.% N HHCCI shows the best corrosion resistance. With the increase of N content, the wear resistance of HHCCI increases. The wear resistance of HHCCI with 0.15 wt.% N is the best, which is 1.57 times that of HHCCI without N.

Microstructure evolution and corrosive wear of heat-treated silicon-bearing hypereutectic high-chromium cast iron

Microstructure evolution and corrosive wear of heat-treated silicon-bearing hypereutectic high-chromium cast iron

Effect of Carbon and Cooling Rate on the Structure of Hypereutectic High Chromium Cast Iron in the Cast State and after Heat Treatment

The article presents experimental data on the changes in the structural parameters and properties of castings from high-chromium cast iron G-X300CrMo27-1 depending on the carbon content, which ranged from 2.8 to 4.5 wt. %. Castings were obtained under cooling conditions with two cooling rates—0.083–0.117 °C/s and 4.67–5 °C/s. Changes in the structure and properties of these castings after destabilizing annealing and subcritical heat treatment were assessed. Changes in carbon concentration and cooling rate in the crystallization interval have a significant effect on the sizes of primary carbides (Cr, Fe)7C3, and on the fraction of eutectic carbides. The microprobe analysis results indicating the effects of cooling rate on the composition of phases in cast iron castings with carbon contents of 4.2 wt. % are presented. The offset value of the crystallization onset temperature and eutectic point with an increase in the cast iron melt cooling rate from 0.083 to 0.83 °C/s is shown. The changes found in the properties of castings with increases in carbon concentration and cooling rate cannot be unambiguously explained by the transformation of the structure of primary and eutectic carbides and changes in the elemental composition of phases. The composition and condition of the matrix has a significant effect on the hardness, bending strength and abrasion resistance of castings. It is suggested that internal stresses arising in primary and eutectic carbides affect the properties of castings in the cast and heat-treated state.

Study on Simulation of Mold Filling and Solidification Characteristics of Hypereutectic High-Chromium Cast Iron by Lost Foam Suspension Casting

In this paper, the finite element software ProCAST version 14.5 was used to simulate the temperature field, flow field and defect prediction in the filling and solidification process of hypereutectic high-chromium cast iron. The effects of pouring temperature, negative pressure and the amount of suspension agent added during the technological process were explored. The optimum process parameters were presented. It was found that the suspension agent has a certain hindrance to the filling process, but the filling process remains stable. In the solidification stage, 89.4% of the suspension agent melted, resulting in a relative supercooling degree of 50 °C, which had a certain chilling effect and improved the solidification rate.

EFFECT OF QUENCHING HOLDING TIME ON MICROSTRUCTURE AND PROPERTIES OF HIGH SILICON HYPEREUTECTIC HIGH CHROMIUM CAST IRON

In this paper, the effects of different quenching holding times on the microstructure and properties of high-silicon hypereutectic high-chromium cast iron (Fe–4.0C–35.0Cr–1.9Si) were investigated. The effect of quenching holding time on the microstructure of high silicon hypereutectic high chromium cast iron was analyzed by optical microscope, scanning electron microscope and X-ray diffractometer. The hardness and wear resistance of high-silicon hypereutectic high-chromium cast iron quenched at 1150∘C for different time were tested by Rockwell hardness tester, microhardness tester and wear tester. The results show that the microstructure of as-cast high-silicon hypereutectic high-chromium cast iron is mainly composed of pearlite matrix and M7C3 carbide. Quenching heat treatment makes part of the matrix transform from pearlite to martensite, and precipitate a small amount of M[Formula: see text]C6 type secondary carbide. With the increase of quenching holding time from 1[Formula: see text]h to 6[Formula: see text]h, the amount of martensite transformation gradually increases, the primary carbide has no obvious change, the eutectic carbide tip dissolves, and the morphology gradually becomes smooth. The hardness and wear resistance both increase first and then decrease. After 4 hours of insulation, the hardness reaches the highest 60.5HRC, which is increased by 3 HRC compared to 1 hour of insulation. The wear resistance increases by 22.1% compared to 1 hour of insulation. At this time, the wear resistance is the best.

Refinement of primary carbides and improvement of wear resistance of hypereutectic high chromium cast iron after modification

The effect of the modification treatment on the refinement of primary carbides and wear resistance of 35% Cr-4.0% C hypereutectic high chromium cast iron (HHCCI) was investigated using the first-principles calculations, XRD, SEM, TEM, hardness tests, and wear tests. The addition of N elements to HHCCI refined the size of the M7C3 primary carbide from 13.25 ± 0.72 μm to 11.67 ± 0.33 μm under the effect of adsorption refinement. When the compound modification elements (N + Ti + V + RE-Mg) were added, the combination of adsorption refinement and heterogeneous nucleation refinement significantly reduced the carbide size to 5.35 ± 0.15 μm. The refinement of the M7C3 primary carbide can be attributed to two components: 1) the refinement of the heterogeneous nucleation of TiC and VC. 2) the combination of N, Ti, and V with the M7C3 preferred growth surface (0001) resulting in the refinement by adsorption and reduce the size of the primary carbide. The hypereutectic high chromium cast iron after the compound modification exhibited excellent wear resistance. Under dry sliding wear condition, Compared with the unmodified sample, the wear resistance increased by 75%. Under corrosive wear conditions, the wear resistance is increased by 98.1%.

Effect of interlayer temperature and extremely low terminal cooling temperature on the microstructure and wear resistance of Fe-based hardfacing alloy

Hypereutectic high chromium cast iron (HHCCI) coatings were prepared by flux-cored arc welding (FCAW) under 230 °C, 80 °C and 30 °C interlayer temperatures, and an extra liquid nitrogen cooling was used to obtain −125 °C terminal cooling temperature. The microstructure evolution mainly primary carbide (P–C) and matrix, and abrasive wear behavior were evaluated. For natural air cooling, the amount of primary carbide increased, and the size and the mean free path between P–C decreased, with the decrease of the interlayer temperature. Due to the anisotropy in the P–C shape, the volume fraction of P–C, expressed by the area fraction, was significantly affected by the growth orientation. Liquid nitrogen cooling further optimized the morphology of P–C, in terms of the amount, size and distribution. Due to the −125 °C terminal cooling temperature, the martensitic transformation developed in the matrix, showing a body-centered tetragonal structure and exhibiting a Kurjumov-Sachs (K–S) orientation relationship with parent austenite. The linear relationship between wear resistance and P–C was investigated by Pearson's correlation coefficient, and the amount, size and mean free path expressed a strong correlation with wear resistance. Finally, the coating cooled by liquid nitrogen showed the best wear resistance, owing to the excellent morphology of P–C, and the strengthened matrix.

Corrosion Wear of Hypereutectic High Chromium Cast Iron: A Review

Hypereutectic High Chromium Cast Iron (HHCCI) is a new type of corrosion-wear-resistant material developed from ordinary high chromium cast iron by increasing the chromium and carbon content and is often used in abrasive environments where wear and corrosion interact. The corrosion wear resistance of the HHCCI is related to the number, size, shape and distribution of carbides and the microstructure of the matrix. This paper reviews the research progress in improving the corrosion wear resistance of HHCCI from various aspects such as primary carbide refinement, heat treatment, deep cooling treatment and alloying, etc. Among the methods of refining primary carbides are modification, semi-solid treatment and current pulse treatment. In addition, we also analyze the potential of Cr, V, Nb, Mo, Mn, W, Ni, Cu, Si, N and other alloying elements to improve the corrosion wear resistance of HHCCI. The mechanism for improving the corrosion wear resistance of HHCCI is also explored in depth and research contents worthy of attention are proposed to further improve the corrosion wear resistance of HHCCI. In the future, the author believes that modification + alloying + heat treatment is the most potential application method to improve the corrosion wear resistance of HHCCI. The corrosion wear resistance of HHCCI can be further improved by refining the primary carbide (such as adding rare earth, Ti and other modified elements) + heat treatment (with cryogenic treatment) to improve the strength + alloying (such as adding low-cost, high-potential alloy elements such as N and Si) to improve the corrosion wear resistance of the matrix.

The influence of cooling rate on the structure and properties of castings of hypereutectic high-chromium cast iron when they are modified with B, Bi, Sb, Sn, Ca

<abstract> <p>The article presents the results of a study of the influence of B, Bi, Ca, Sn, and Sb additives on the structure, composition, and properties of individual phases and mechanical properties of castings made of hypereutectic high-chromium cast iron (HCCI), similar in composition to G-X300CrMo27-1 cast iron. Additives of these elements were introduced into the melt before cooling at an amount of 0.2 wt.%. The ingots were obtained at a melt cooling rate in the crystallization range of 0.083–0.116 ℃/s and at 4.67–5 ℃/s. When studying the structure, the parameters and proportion of primary carbides, and the proportion of eutectic carbides were determined and a description was given of the change in the austenitic matrix. Using microprobe analysis and microhardness measurements, changes in the composition and hardness of primary, eutectic carbides and the matrix were determined. Hardness HV, bending strength, and abrasive wear resistance were determined. It has been shown that depending on the cooling rate, the effect of these additives on the structure and properties of castings changes. The mechanism of influence of these elements on the process of crystallization of primary carbides in HCCI is considered. Based on the data obtained, it is proposed to use Ca as a modifying additive when producing castings from HCCI of a hypereutectic composition under slow cooling conditions, and B under fast cooling conditions. This makes it possible to increase the wear resistance of castings.</p> </abstract>

Microstructure and properties of Cu-bearing hypereutectic high chromium cast iron

Microstructure and properties of Cu-bearing hypereutectic high chromium cast iron

Effect of quenching temperature on microstructure and properties of low silicon hypereutectic high chromium cast iron

In this paper, the effects of different quenching temperatures on the microstructure and properties of Fe–4.0C–35.0Cr–0.5Si (wt.%) low-silicon hypereutectic high-chromium cast iron (LS-HHCCI) was investigated. The effect of quenching temperature on the microstructure of LS-HHCCI was analyzed by optical microscope, scanning electron microscope, and X-ray diffractometer. After quenching at different temperatures, the hardness and wear resistance of LS-HHCCI were tested by Rockwell hardness tester, microhardness tester, and wear testing machine. The results show that the microstructure of as-cast LS-HHCCI is mainly composed of austenite matrix and M7C3 carbides. After quenching, the austenite matrix is transformed into martensite, and M23C6 type secondary carbides are precipitated in the matrix. As the quenching temperature increased from 950 °C to 1100 °C, the eutectic carbides first appeared as fine needles, and then they gather and grow up, showing elongated or lumpy. The hardness and abrasion resistance first increase and then decrease, it reached peak values of 67.2 HRC at the temperature of 1050 °C, while the wear resistance is the best.

First-principles study on corrosion resistance of copper-bearing hypereutectic high chromium cast iron

Based on the Tafel formula, Butler-Volmer equation, and first-principles calculations, the bulk model, surface model, and polarization prediction curve of the Hypereutectic High Chromium Cast Iron (HHCCI) matrix were constructed. The results show that the predicted corrosion current density (2.19×10 -5 A·cm 2 ) of the copper-bearing HHCCI matrix is lower than the measured corrosion current density of the copper-bearing HHCCI (4.41×10 -5 A·cm 2 ) under the acidic condition of pH=1. In the neutral environment of pH=7, the corrosion resistance of HHCCI is better than that of HHCCI under acidic conditions. The predicted corrosion current density of the copper-bearing HHCCI matrix (4.39×10 -10 A·cm 2 ) is also smaller than that of copper-free HHCCI (7.98×10 -10 A·cm 2 ), which shows that the corrosion resistance of copper-containing HHCCI matrix is better than that without copper from the perspective of first-principles calculation. Combined with the electrochemical experimental results, it can be seen that the corrosion potential (-409.76 mV) of 1.5 wt.% Cu HHCCI is significantly higher than that of 0 wt.% Cu HHCCI (-450.34 mV). The trend of the electrochemical test results is consistent with the predicted trend of the calculated polarization curve, which indicates that copper alloying can improve the corrosion resistance of HHCCI. Predicted polarization curves on γ-Fe (100) surfaces (PH=1): (a) γ-Fe (Cu-Free); (b) γ-Fe (Cu-Bearing) • Predicting corrosion resistance using equations and first-principles. • Copper improves the predicted current density of HHCCI matrix at pH=1. • Copper improves the current density of HHCCI at electrochemical experiments. • Copper alloying improves HHCCI corrosion resistance.

Effect of Si on Microstructure and Wear Resistance of Hypereutectic High-Chromium Cast Iron

Effect of Si on Microstructure and Wear Resistance of Hypereutectic High-Chromium Cast Iron

Effects of destabilization and tempering on microstructure and mechanical properties of a hypereutectic high-chromium cast iron

Effects of destabilization and tempering on microstructure and mechanical properties of a hypereutectic high-chromium cast iron

Microstructure and properties of modified as‐cast hypereutectic high chromium cast iron

AbstractThe present work studied the effects of different modification treatments on the microstructure and mechanical properties of hypereutectic high chromium cast iron containing about 35 wt% chromium and 4.0 wt% carbon. It was found that the primary carbides in the hypereutectic high chromium cast iron were all refined to different levels after different modification treatments. Among them, the best result was obtained by adding 0.6 wt % rare earth magnesium, and its average carbide diameters was 43 μm, which is almost half of the unmodified specimen. After modification, the mechanical properties have been improved, and the refinement of primary carbides can greatly improve its impact toughness. The impact toughness of the specimen modified by adding 0.6 wt % rare earth magnesium was the largest, reaching 7.0 J cm−2, and the impact toughness of un‐modification specimen was the worst, only 4.5 J cm−2. The refining of primary carbides does not have much effect on the hardness. The hardness of the sample with 0.6 wt % rare earth magnesium and 0.3 wt % TiBAl is the highest, and its value is 58.0 HRC. The wear resistance increases with the refinement of primary carbides.

Effect of heat treatment on microstructure and properties of modified hypereutectic high chromium cast iron

Abstract The effect of heat treatment on the microstructure, hardness and wear resistance of modified hypereutectic high chromium cast iron (HCCI) was investigated. The results show that the quenching treatment partially dissolves the edges of the primary carbides, and the sharp corners become rounded and blunt. As the quenching temperature increases, the carbide re-dissolves into the matrix, and the hardness and wear resistance first increase and then decrease. The hardness and wear resistance are the best when quenched at 1000 °C. After tempering, the martensite is transformed into tempered martensite, and the precipitation of secondary carbides increases. As the tempering temperature increases, the secondary carbides gradually become coarser. When the tempering temperature is 500 °C, the hypereutectic HCCI shows the highest hardness and the best wear resistance. When tempered at 400 °C, hypereutectic HCCI shows the best erosion and wear resistance.

Effect of TiB2 addition on microstructure and mechanical properties of a hypereutectic high chromium cast iron

Effect of TiB2 addition on microstructure and mechanical properties of a hypereutectic high chromium cast iron

EFFECT OF CARBON CONTENT ON MICROSTRUCTURE EVOLUTION AND PROPERTIES OF HYPEREUTECTIC HIGH CHROMIUM CAST IRON

This study is to reveal the influence of the amount of carbon content on the microstructure evolution, mechanical properties, and wear properties of Hypereutectic High Chromium Cast Iron (HHCCI). The results indicated that the carbon content plays a key role in the regulation of carbides in the cast iron microstructure. As the amount of carbon content rises, the primary carbides in the cast iron microstructure become apparently coarser, and the volume fraction of carbides gradually increases. The carbide volume fraction reaches 62% when the carbon content is 5[Formula: see text]wt.%. When the value of the carbon content increases, the accumulation and growth of eutectic carbides in the heat-treated cast iron become more and more obvious. After heat treatment, a large number of secondary carbides will be precipitated from the austenite matrix, in the form of fine particles or short rods, with a dispersed distribution. The macroscopic hardness of HHCCI has increased. When the carbon content is 3.5[Formula: see text]wt.%, the macroscopic hardness is 61.2 HRC, and when the carbon content becomes 5[Formula: see text]wt.%, it reaches 64.3 HRC. The wear resistance of HHCCI increases with the value of the carbon content increases. When the carbon content was increased from 3.5[Formula: see text]wt.% to 5.0[Formula: see text]wt.%, the wear resistance of the material increased by 85.7%. The wear of HHCCI is mainly adhesive wear and fatigue wear, and the wear morphology is mainly spalling pits and wear debris.

Microstructural and Erosive Wear Characteristics of a High Chromium Cast Iron

Surface material loss due to erosive wear is responsible for the increased cost of maintenance and downtime in industries. Hence, hardfacing is one of the most valuable and effective techniques employed to improve the wear resistance of heavy-duty components. The present paper investigates the microstructural and erosive wear characteristics of a hypereutectic high-chromium cast iron, considering the erosion resistance, resulting from the impact of micro-sized particles, of both as-received and heat-treated conditions. Micro-sized particles involve the erosion-resistant characteristics of carbide and matrix, contemporary. Due to this, the enhancement of the matrix strength could improve the mechanical support to withstand cracking deformation and spalling. Accordingly, the effect of a destabilization heat treatment on the microstructure was firstly investigated by hardness tests, X-ray diffraction analyses, optical and scanning electron microscopy. Specifically designed erosive tests were carried out using a raw meal powder at an impingement angle of 90°. The resulting superior wear resistance of the heat-treated samples was relayed on the improved matrix microstructure: consistent with the observed eroded surfaces, the reduced matrix/carbides hardness difference of the heat-treated material is pivotal in enhancing the erosion resistance of the hardfacing. The present results contribute to a better understanding of the microstructure–property relationships concerning the erosive wear resistance.