Microstructure Of Cast Iron Research Articles

Microstructure of spheroidal graphite aluminum-alloyed cast irons (SGAACI) containing up to 7.5 wt% produced via in-mold process

In the present research work, the effect of various aluminum contents on the microstructure of spheroidal graphite cast irons produced via the in-mold process was investigated. Samples containing 0, 3.7, 5.5, 6.4 and 7.5 wt% aluminum were cast and characterized by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction analysis (XRD) and hardness test. It was observed that by increasing the Al content from 0 to 7.5 wt%, the micro-hardness of pearlite and ferrite phases increases by 228 and 254 Vickers, respectively. Moreover, the addition of aluminum led to an increase in the nodule count from 168 to 668 per mm2, reduction in the nodule diameter from 21.4 to 8.8 µm and also reduction in the sphericity from 65 to 48%. The obtained results revealed that varying aluminum content affects the precipitated pearlite morphology. This seems to be the result of aluminum reaction with carbon and the change in both carbon activity and rate of diffusion and also the aluminum atom behavior in the solid solution of Fe–Al–C alloys.

Influence of Sn and Nb additions on the microstructure and wear characteristics of a gray cast iron

Effects of Sn and Nb additions on the microstructure and wear behavior of a gray cast iron (GCI) have been investigated in details. The results showed that the combined additions of Sn and Nb not only promote the generation of pearlite and type-A graphite but also refine the graphite flakes size and the pearlite lamellar spacing. The analysis results of wear test indicated that the GCI-Sn–Nb sample with higher hardness (201 HB) yields a decreased mass loss by 63% compared to the GCI sample. Moreover, the GCI sample displays a severe wear in which some larger crater and a coarser surface can be observed, while the wear morphology of the GCI-Sn–Nb sample looked smooth, and the crater was smaller than the others. Under the present wear test condition, the combined additions of Sn and Nb are likely to improve the wear resistance of gray cast iron. The enhanced wear resistance of GCI-Sn–Nb sample was closely correlated to the increased hardness caused by the increase in pearlite content and the refinement of the graphite flakes size and the pearlite lamellar spacing.

Precipitation of M23C6 Secondary Carbide Particles in Fe-Cr-Mn-C Alloy during Heat Treatment Process

The initial as-cast microstructure of high-chromium white cast iron (2.08% C, 12.1% Cr), including austenitic dendrites in a matrix of a eutectic mixture of austenite and M7C3 carbides. Heat treatment of as-cast iron leads to a transformation of the matrix from austenite to martensite phase. The secondary M23C6 carbide precipitated from matrix improving the hardness of sample from 48 HRC to 62 HRC. JMatPro simulations of volume fraction phase for Fe-C-Cr-Mn alloy shows M7C3 and austenite phases are stable at austenitization temperature (1000 °C). Eutectic carbide of M7C3 is a stable phase in the alloy which is undissolved in the matrix during the heat treatment process. The HR-TEM images of heat-treated sample revealed that both eutectic M7C3 carbide and ultrafine secondary M23C6 carbide particles distributed on the martensite matrix.

Effect of Cu and Mo addition on mechanical properties and microstructure of grey cast iron: An overview

The addition of any alloying element alters the various properties of developed alloy, wherein mechanical properties influence significantly. The present work reviews the effect of molybdenum (Mo) and copper (Cu) addition in grey cast iron. It alters the few mechanical properties such as tensile strength, hardness and toughness of grey cast iron and are covered in this review article. It is reported that on increasing the percentage of copper and molybdenum in grey cast iron, tensile strength and hardness increases and impact energy decreases. But, beyond a certain amount of copper and molybdenum addition, there is a negligible effect on the hardness. Thus the main role of copper and molybdenum addition, is to reduce the volume of graphite flakes and increase the content of pearlite in microstructure of gray cast iron.

Effect of silicon addition on microstructure and mechanical properties of grey cast Iron: An overview

Grey cast iron is used to make brake disc due to its high damping vibration resistance and low cost. In the present work, effect of silicon addition on microstructure and mechanical properties of grey cast iron is reviewed. Results of microstructure and mechanical properties are compiled, which are affected due to the addition of silicon in grey cast iron. From the review, it is found that the volume of soft graphite flakes increases i.e. grain size increases which reduces the hardness of grey cast iron, on increasing the silicon content. Similarly, tensile strength reduces as a function of silicon addition. Hardness and wear rate depends on the phase of microstructure and the size of graphite flakes. Maximum hardness was obtained at 3.33% of silicon content.

Effect of the Time and Temperature of Isothermal Quenching on Microstructure and Mechanical Properties of Bainitic Gray Cast Iron

Effect of the Time and Temperature of Isothermal Quenching on Microstructure and Mechanical Properties of Bainitic Gray Cast Iron

中锰马氏体铸铁在不同热处理下组织与性能研究

中锰马氏体铸铁在不同热处理下组织与性能研究

Influence of S and Mn on mechanical properties and microstructure of grey cast iron: An overview

In the present review article, influence of S and Mn on microstructure and mechanical properties is studied. Additionally, effect of manganese and sulfur on the wear property of grey cast iron was also reviewed. The data from different experiments were taken under consideration and studied for the examination of the alloyed cast iron. The study describes that on increasing the manganese content of the grey cast iron, wear coefficient and hardness decreases and impact energy increases. The main motive of addition of manganese is to control the adverse effect of sulfur on the mechanical properties of grey cast iron. Moreover, the presence of manganese counter the formation of FeS, which is the reason for hot shortness in the alloy.

Model of assessment of the hardness of the iron rollers СПХН-43 and СШХНФ-47

Relevance of the article. The quality criteria of massive metal products is affected by many technological parameters. Changing some of these parameters can lead to a significant change in the quality of the target product. Therefore, various types of models are widely used in materials science to simulate individual processes or predict individual criteria. An analysis of literary sources indicates the prospects of using fractal geometry to model the structure and properties of various materials. It is proposed to apply multifractal analysis to assess the structure of cast-iron rolls. Materials and methods. The influence of the structure of cast irons on their hardness was investigated. The microstructure of cast iron was investigated using quantitative methods of metallography (ГОСТ 3443) and multifractal analysis. The calculation of the spectrum of statistical dimensions of the cast iron microstructure was carried out according to the Renyi formula. The hardness indices of the roll-forming rolls СПХН-43 (520 ´ 1 000 mm) and СШХНФ-47 (680 ´ 1 000 mm) were determined at three points evenly spaced along the length of the roll barrel. Results and its discussion. The influence of the spectrum of statistical dimensions D 0 , D 1 , D 2 , D -100 and D 100 of carbides, lamellar and spherical graphite on the hardness indices of cast iron rolls is studied. It was found that the pair correlation coefficients in the prediction of hardness according to the traditional characteristics of the structure (length, diameter, area) are R 2 = 0,73...0,87. The correlation coefficients in the prediction of hardness by multifractal characteristics for rolls СПХН-43 are 0,78...0,88. For rolls СШХНФ-47, the correlation coefficients are 0,81...0,93. The obtained results confirm the effectiveness of using multifractal analysis in assessing the quality criteria of cast-iron rolls. Scientific novelty. The influence of multifractal dimensions of graphite and carbides on the hardness of cast iron rolls СПХН-43 and СШХНФ-47 is established. The sensitivity of the СПХН-43 roll hardness indices to the information and correlation dimensions of carbides, as well as to the fractal and statistical D -100 dimensions of plate graphite, was revealed. The sensitivity of hardness indices to the fractal and statistical D 100 dimensions of carbides and to the fractal and correlation dimensions of spherical graphite was established for the СШХНФ-47 rolls. Conclusions. Based on the results obtained, an approach has been developed to assess the hardness indices of rolls СПХН-43 and СШХНФ-47, which includes: 1) Determination of the spectrum of statistical dimensions of structural elements of cast irons. 2) Determination of sensitivity coefficients of hardness indicators to the spectrum of dimensions of structural elements. 3) Construction of a mathematical model for forecasting roll hardness. The approach considered can be interpreted as an alternative method for assessing the quality criteria of cast irons based on an analysis of their structure.

Study of the effect of graphitized annealing on microstructure of chromium-nickel cast iron

Study of the effect of graphitized annealing on microstructure of chromium-nickel cast iron

The effect of niobium addition on the microstructure and properties of cast iron used in cylinder head

Cylinder head is one of the most important parts of heated components in the engine, while cracking due to low strength and large residual stress at high temperature is the main failure mode of cylinder head. With the growing demand of good performance and high reliability, gray cast iron with trace alloying element and optimized annealing process are probably effective ways in obtaining suitable materials. The effect of niobium addition on the microstructure and properties of cast iron used in cylinder head is studied in this paper. The results show that, the tensile strength, toughness, fatigue properties and thermal fatigue properties of gray cast iron are improved by adding trace niobium elements. The specimen with 0.20% niobium shows better comprehensive mechanical properties than others. The addition of trace niobium elements can not only refine the graphite, eutectic cell, carbide and phosphorus eutectic, but also reduce the pearlite lamellar space, thus strengthening the matrix. The cylinder head is made by cast iron with 0.20% niobium addition, and the annealing process of thermal aging is optimized. The residual stress of cylinder head can be maintained at a low level by adopting annealing process with higher holding temperature, longer holding time, lower cooling rate and lower outlet temperature. The analysis of microstructure, mechanical properties and residual stress for niobium alloyed cast iron is helpful for solving the cracking problem of cylinder head, and providing scientific basis for improving engine reliability.

Effect of liquid-solid volume ratios on the interfacial microstructure and mechanical properties of high chromium cast iron and low carbon steel bimetal

Bimetal casting made of high chromium cast iron (HCCI) and low carbon steel (LCS) was produced by liquid–solid casting technology. The influence of different liquid-solid volume ratios on microstructure and microhardness of the interface was studied. The interface microstructure and the elemental distribution from one side to the other side of the bimetal were analyzed using Energy Dispersive x-ray Spectroscopy (EDX). Wear behavior of the successfully produced bimetal was also investigated in order to emphasize the difference in the mechanical properties between the two bonded alloys. The results showed that a good metallurgical bonding area free of holes could be obtained with increasing the liquid to solid volume ratio to 10:1 and 12:1. By increasing this ratio, diffusion of the elements was accelerated resulting in expanded carbide-free zone and improved bonding of the bimetal. Accordingly, the microhardness decreased at the HCCI side and increased at the LCS part due to the elemental diffusion from the former to the later through the interface. Sliding wear test on both sides of the bimetal showed that the coefficient of friction was ∼0.79 for HCCI and 0.69 in case of LCS. The transition from the high wear resistant HCCI part to LCS was significantly observed on the worn surface of the interfacial area of the test sample. The wear mechanism involved in the two sides was delimitation and the size of the produced laminates was smaller in case of LCS than in HCCI.

Stable Eutectic Formation in Spray-Formed Cast Iron

Spray forming is an advanced casting process that produces refined and homogenous microstructure directly from the liquid metal regardless of the alloy system. However, the microstructure evolution during spray forming is complex because the process comprises two sequential steps with very different cooling rates, i.e., atomization and deposition. It is well known that the microstructure of cast irons is highly dependent on the chemical composition and the cooling rate imposed to the liquid. In order to better understand the microstructural evolution during solidification by spray forming, this study investigated the solidification of two cast irons with different stable–metastable eutectic temperature interval (ΔTES−M), 30 K and 17 K. The microstructures of both overspray powders presented a dendritic array of austenite with cementite in the inter-dendritic spacing. Despite the high cooling rates imposed to the alloys during the atomization step, the final microstructure was defined by the cooling conditions prevailing during the final step of deposit solidification and stable eutectic was formed. This was ascribed to the dynamic process involving heating and remelting of the low melting temperature phases present in the droplets that arrives completely or partially solid in the deposition zone.

Effect of alloying elements W, Ti, Sn on microstructure and mechanical properties of gray iron 220

Experiments were carried out to observe the variation in microstructure and mechanical properties of gray cast iron by adding pearlite promoting alloying elements such as Ti, Sn and W. Results show that adding Sn, Ti, and W with different concentrations improve the microstructure, Brinell hardness and tensile strength of gray cast iron. With the increase of alloying element concentration, the average graphite length and graphite content increase linearly. At the same time, average cell size and the maximum graphite length also decrease linearly. Brinell hardness and tensile strength of gray cast iron also increase with an increase in alloying elements contents, and attain the maximum when Ti = 0.561%, Sn = 0.561% and W = 0.945%. However, at higher concentrations of Ti = 0.810%, Sn = 0.631% and W = 1.351%, the tensile strength decreases from 333 MPa to 297 MPa and the Brinell hardness decreases from 248 HB to 225 HB. The decrease in tensile strength and Brinell hardness at the higher concentration level is attributed to the formation of coarse and thick graphite flakes.

An Investigation of Effect of Tin (Sn) on Microstructures and Mechanical Properties of Gray Cast Iron

As the tensile strength of gray cast iron is low, it is tried to increase tensile strength by testing various alloying elements. The most preferred of these alloying elements was the copper element. However, it is known that copper increases both hardness and tensile strength by enhancing perlite ratio in microstructure. On the other hand, when tin (Sn) is used in trace amounts compared to copper, it has similar effects on hardness and tensile strength of cast iron. In this study, adding tin element of 0,03-0,06-0,09-0,12-0,15 % by weight in gray cast iron, its effect on tensile strength was investigated and the appearance of the fracture surfaces was examined. It was compared with two different gray cast irons containing 0.4% copper element and free of alloying elements. According to the tensile strength results, the highest tensile strength was observed to be 195 N / mm2 in the specimen number 6 containing 0,12% Sn. The lowest tensile strength was determined as 157 N / mm2 in the specimen number 1 which did not contain alloying elements. In SEM (Scanning Electron Microscopy) images, it is seen that the samples generally exhibit a brittle rupture behaviour. In some of the specimens with the addition of tin and copper, regional ductile rupture behaviours were observed.

Effect of tellurium on microstructure of low-alloy cast iron deposited by electroslag method in current-carrying mold

Effect of tellurium on microstructure of low-alloy cast iron deposited by electroslag method in current-carrying mold

Влияние теллура на микроструктуру низколегированного чугуна, наплавленного электрошлаковым способом в токоподводящем кристаллизаторе

Влияние теллура на микроструктуру низколегированного чугуна, наплавленного электрошлаковым способом в токоподводящем кристаллизаторе

Wear and corrosion resistance of Cr2O3%-40%TiO2 coating on gray cast-iron by plasma spray technique

In this study, lamellar graphite cast iron was coated with atmospheric plasma spraying (APS) technique. Cr2O3-40%TiO2 ceramic composite powder was used as a coating powder. The microstructure and mechanical properties of cast iron and coating were assessed. The new coating surfaces were analyzed by optical microscope (LM), scanning electron microscope (SEM) and energy dispersive x-ray spectroscopy (EDS). Micro-hardness tests were carried out with 200 g load (Wolpert micro hardness device). Wear tests were performed with a reciprocating wear test device under normal atmospheric conditions (room temperature and 30% humidity) while corrosion tests were performed in a glass cell according to ASTM standards (G1-03, G5-94) in three electrode techniques at room temperature in 3.5% NaCl solution. The results show that the coating microstructure is porous, micro-cracked and contains some non-homogenous structures such as oxide. Based on the EDS analysis, the presence of the existing phases revealed that the coating process was successful. In addition, the presence of hard particles in the coated surface layer increased the hardness of the composite coating compared to that of cast iron. Accordingly, the wear resistance was also high. The Cr2O3-40%TiO2 coating showed an improved corrosion resistance compared to the uncoated cast iron sample.

Microstructure and Tribological Properties of Spheroidal Graphite Cast Irons with Nanoadditives

Microstructure and Tribological Properties of Spheroidal Graphite Cast Irons with Nanoadditives

ASSESSING THE VOLUME FRACTIONS OF THE PHASES, NODULARITY AND NODULE COUNT OF SPHEROIDAL GRAPHITE CAST IRON USING IMAGEJ SOFTWARE

In this study, a simple method for assessing the microstructure of ductile cast iron by using a freeware digital image processing software is described. The method is applied to three different ductile iron grades to assess their ferrite, pearlite and graphite volume fractions as well as graphite nodularity, nodule count, nodule size. All specimens were found to show good nodularity (~ 88 % by area) with different graphite average size and perimeter morphology. The amount of graphite was also found to be similar (11±2 % by area) in all specimens. On the other hand, ferrite percentages were found as 85.8, 57.1, and 52.5 % respectively for ASTM A536 grades 60-40-18, 65-45-12, and 80-55-06. It was also found that among these three grades, the higher the pearlite content, the higher the hardness. The agreement with the standards confirms that quantitative metallography through image processing is a powerful tool in order to estimate the mechanical properties of cast irons.