Alloy White Iron Research Articles

Effect of Cu addition on hardness and microstructural features of low alloy white cast iron

The aim of this work is to investigate in details the effect of Cu on hardening variation and microstructural feature of low alloy white cast iron. For this purpose, a wide variety of iron melts consisting of different weight percent Cu were prepared with step by step addition of about 0.5%Cu to a constant base chemical composition of low alloy white iron. Hardness measurements were supplemented with x-ray diffraction, colored light metallography and electron microscopy to follow the relationship between hardness and microstructure of as-cast white irons. The experimental results show that as-cast hardness has been sequentially increased from 49HRC to the values of 52, 57 and 61HRC with step by step addition of only about 0.5%Cu to the chemical composition of low alloy base melt iron, respectively. The remarkable improvement of as-cast hardness has been rationalized to the formation of more and more displacive martensitic phase transformation products developed as a consequence of alloying partitioning within the associated austenite and carbide during solidification. The M3C eutectic carbide is just rich in Cr while the austenite phase, apart from a significant enrichment of Mn, Ni and Cu, has been surprisingly enriched from Mo as well.

Influence of Particle Size of Wheat Powder on Roller Wear Properties

Wheat milling process involves multiple grinding procedures, the wheat powder particles size in different grinding procedure are difference. In order to study the influence of particle size of wheat powder on roller wear performance in different grinding procedure, abrasion experiments were carried out by MLS-225 three-body abrasive wear tester, while different sizes were chosen as abrasive, alloy white iron which frequently used as roller metal materials was chosen as wear sample, wear weight loss and surface microstructure were chosen as the main evaluation indicators. The results showed that the weight loss of samples were showed a linear relationship with wheat the size of wheat powder. The main wear behavior was mainly mechanical polishing while particle sizes was smaller one. For the larger size, wear was made by multiple plastic deformation and low cycle fatigue wear mechanism.

Correlation of microstructure with the wear resistance and fracture toughness of white cast iron alloys

The objective of this investigation was to set down (on the basis of the results obtained by the examination of white cast iron alloys with different contents of alloying elements) a correlation between chemical composition and microstructure, on one hand, and the properties relevant for this group of materials, i.e., wear resistance and fracture toughness, on the other. Experimental results indicate that the volume fraction of the eutectic carbide phase (M3C or M7C3) have an important influence on the wear resistance of white iron alloys under low-stress abrasion conditions. Besides, the martensitic or martensite-austenitic matrix microstructure more adequately reinforced the eutectic carbides, minimizing cracking and removal during wear, than did the austenitic matrix. The secondary carbides which precipitate in the matrix regions of high chromium iron also influence the abrasion behaviour. The results of fracture toughness tests show that the dynamic fracture toughness in white irons is determined mainly by the properties of the matrix. The high chromium iron containing 1.19 wt% V in the as-cast condition, showed the greater fracture toughness when compared to other experimental alloys. The higher toughness was attributed to strengthening during fracture, since very fine secondary carbide particles were present mainly in an austenitic matrix.

Improved Color Metallography for a Low Alloy Hardened White Cast Iron

In this experimental work, several single and double chemical color etching techniques have been developed to identify in details the as cast optical microstructural observation in a low alloy as cast hardening white iron. The etching techniques are based on the various metallographic reagents involving 2%nital, Marshall's, Glyceregia, 5%ammonium persulfate, Kalling's NO.1 and aqueous ferric chloride chemical solutions. Evidence is presented which indicates that the microstructural components including retained austenite, martensite, pearlite, secondary and M 3 C eutectic carbides can be distinguishable colorful from each other in the multiphase white cast iron microstructure. The results indicate that the retained austenite has been appeared in a good contrasting resolution by different colors such as brilliant green and brilliant white after using double etching procedures consisting of Marshall's followed by Kalling's NO.1 and Marshall's with the subsequent use of 5%ammonium persulfate respectively, while the martensite is stained by lightly brown color after using these associated double metallographies. The martensite has been also colored by sharply contrasted brilliant brown after using a single etching technique of 5%ammonium persulfate. The secondary carbide has been stained in a good contrasting observation as dark and bright particles with double etching techniques based on the Marshall's followed by Glyceregia and Marshall's with aqueous ferric chloride solutions, respectively. The X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) micrographs are confirmed the as cast optical microstructural evolution developed in the low alloy white iron.

Determination of wear coefficients for erosive wear prediction through Coriolis wear testing

In simulation of erosive wear on wet-end components (i.e. casing, impeller and liners) of centrifugal slurry pumps using numerical models, the determination of wear coefficients is critical to achieve reasonable and consistent accuracy on wear life prediction. In the present research, work relevant to the Coriolis wear tester is briefly reviewed. Through Coriolis wear testing and analysis, wear coefficients (or specific energy coefficients) have been determined for different slurry conditions over a large range of particle sizes. Several types of wear resistant white iron alloys including that specified in ASTM G75 were selected as target materials in this study. Considering the fact that many wear models assumed mono particle size, slurries with wide, narrow and semi-narrow banded (D50/D85 size) solids particles were used during the Coriolis wear tests to investigate the impact of particle distribution on wear coefficients. The test results obtained showed that the wear rates (and so the wear coefficients) of all tested materials increase rapidly over a broad particle size range. Beside particle sizes, other particle properties such as particle shape and size distribution also exhibited significant effect on the values of wear coefficients. Silica sand and copper ore slurries were used as examples. Within the examined target materials, the wear coefficients and wear resistance had relatively strong correlation with the hardness of the materials. Correlation deviations have also been explained from the viewpoint of material microstructures.

Fracture toughness of high-chromium white irons: Influence of cast structure

The fracture toughness of two high-chromium white iron alloys in the as-cast condition has been investigated. Fracture toughness test pieces were extracted at various orientations relative to the columnar macrostructure. The toughness of a 27 Cr white iron alloy was very sensitive to orientation, and the toughness was much larger when the crack propagated in a direction perpendicular to the long dimension of the eutectic carbides. The toughness of the 15-3 Cr-Mo white iron was insensitive to the orientation. The different fracture behaviour of the two alloys was related to the anisotropy of the eutectic carbide structures in the as-cast material. The limitations in applying quantitative data on the eutectic carbide structure to models of fracture toughness in white iron alloys were illustrated.

Wear of cast-bonded components in a coal pulvesier mill

An investigation has been carried out into the manufacture and field trial of alloy white iron beater plates used to process coal in a KSG coal pulveriser mill. The components were made by the cast bonding process, which involves casting a wear layer onto a steel substrate to form a bimetallic composite product. Four alloy white irons, containing primary and/or eutectic carbide volume fractions ranging from nominally 10 to 40%, were used as the cast overlay in the manufacture of the beater plates. Two replicates of each alloy composition were tested in a mill along with two standard austenitic manganese steel plates. All beater plates completed 3275 h of operation, with the best-performing alloys receiving an additional 3471 h of service in a second campaign. The results showed that increasing carbide volume fraction decreased the wear rate most markedly at sites of low-angle erosion, and that it had a smaller influence at higher angles of abrasive particle attack. Subsequent scanning electron microscopy examination of worn components revealed that the primary mode of material loss at the lower carbide volume fractions was microspalling, with sub-surface fractures occurring within the carbide particles and along carbide-matrix interfaces. Surface microgrooves were more evident in the alloy white iron beater plates with higher carbide volume fractions.

The effect of heat treatment on the abrasion resistance of alloy white irons

The effect of the temperature and time of the destabilization and sub-critical heat treatments on the abrasive wear behaviour of two high-chromium white iron alloys (15-3 CrMo and 27 Cr) was investigated. The response of each alloy to the destabilization heat treatment and, therefore, the microstructures developed, differed significantly. Pin abrasion tests were conducted, and showed the wear resistance of the 15-3 CrMo alloy to be superior to that of the 27 Cr alloy for most conditions. Following abrasion testing, retained austenite measurements using X-ray diffraction and microhardness measurements on the wear pins indicated the extent of austenite transformation and work-hardening. The work-hardening due to abrasion was greater for the 15-3 CrMo alloy and this was related to the difference in composition of the matrix of each alloy. Abrasion on garnet and on alumina produced similar levels of work-hardening for both alloys, despite the differences in the abrasive hardness. Sub-critical heat treatments increased the abrasive wear loss. In particular, the formation of ferrite/carbide aggregates during the sub-critical heat treatment greatly increased the wear rate.

Microstructure-property relationships in high chromium white iron alloys

AbstractHigh chromium white irons are ferrous based alloys containing 11–30 wt-% chromium and 1.8–3.6 wt-% carbon, with molybdenum, manganese, copper, and nickel sometimes added as additional alloying elements. The microstructure of these alloys typically consists of hard primary and/or eutectic carbides in a matrix of austenite or one of its transformation products. The presence of hard alloy carbides results in excellent abrasion resistance and, consequently, these alloys are commonly used for materials handling in the mining and minerals processing industries. Alloy content, solidification parameters, and thermal processing can dramatically alter the microstructure that is produced, and this in turn can influence the properties and hence performance of white iron alloys during service. This review outlines the development of the microstructure in high chromium white irons through solidification and thermal processing. The metallurgical effects of conventional processing techniques are discussed, and ad...

Microstructure-property relationships in high chromium white iron alloys

High chromium white irons are ferrous based alloys containing 11–30 wt-% chromium and 1.8–3.6 wt-% carbon, with molybdenum, manganese, copper, and nickel sometimes added as additional alloying elements. The microstructure of these alloys typically consists of hard primary and/or eutectic carbides in a matrix of austenite or one of its transformation products. The presence of hard alloy carbides results in excellent abrasion resistance and, consequently, these alloys are commonly used for materials handling in the mining and minerals processing industries. Alloy content, solidification parameters, and thermal processing can dramatically alter the microstructure that is produced, and this in turn can influence the properties and hence performance of white iron alloys during service. This review outlines the development of the microstructure in high chromium white irons through solidification and thermal processing. The metallurgical effects of conventional processing techniques are discussed, and advances in aspects such as alloying and cryogenic treatments covered. The results of laboratory abrasion tests are summarised, and the effect of microstructure on the wear properties are discussed. The toughness and impact resistance of white cast irons, which are often thought to represent a limiting factor in their use, is reviewed, with particular regard given to the effects of microstructural constituents.

A New method of preparing iso-hardness plots

A new approach has been used for the preparation of iso-hardness plots, which are very useful in the heat treating of metals and alloys. An alloy white iron containing ~6% Mn, ~5% Cr, and ~3% Cu was heat treated at 800,850,900,950,1000, and 1050 °C and soaked for 2, 4, 6, 8, and 10 h, respectively, at each of these temperatures followed by air cooling. It was observed that, although the hardness varied linearly with soaking time, its variation with soaking temperature was nonlinear. This can be represented as:H = 98.285e2021.33/T + (0.037 - 0.316 × 10- 4T) .t whereH is Vickers hardness;T is soaking temperature in K; andt is soaking time in seconds. The variation in hardness has been discussed in light of microstructural changes that can take place upon heat treating.

Modeling of the Corrosion Behavior and Its Interrelation with the Deformation Behavior and Microstructure in a Newly Developed ∼7.5Mn–5Cr∼3.0Cu Alloy White Iron

Corrosion rate (CR), compressive strength (CS) and fracture strain (FS) were determined for different microstructures generated by heat-treating a newly designed ∼7.5Mn-5Cr-3.0Cu alloy white iron intended to be used for making castings to resist aqueous corrosion under marine conditions. The microstructures were characterized on the basis of size, shape, and distribution of the second phase, which in the present study comprised dispersed (DCs) and massive carbides (MCs). A new term, «distribution factor» (DF), has been evolved to characterize DCs. This factor proved useful in establishing a relationship between microstructure and CR, which can be represented by the expression CR=[C 1 +C 2 (VMC)+C 3 (VMC) 2 ]-(DF) C4 where C 1 , C 2 , C 3 , and C 4 are constants, VMC is the volume fraction of MCs, and DF is the distribution factor representing DCs

Effect of heat treatment on the hardness-microstructure inter-relation in a 7.5Mn-5Cr-1.5Cu alloy white iron: A modeling approach

An experimental study has been made on the effect of heat-treating temperature (800 °C 850 °C 900 °C, 950 °C, 1000 °C, and 1050 °C) and time (2, 4, 6, 8, and 10 hours) on the transformation behavior of a 7.5Mn-5Cr-1.5Cu white cast iron developed to resist aqueous corrosion in different environments. Structural changes on heat treating were monitored using hardness measurements. It was observed that on heat treating from 800 °C, hardness increased marginally with soaking period. Hardness was independent of soaking period on heat treating at 850 °C and 900 °C. On heat treating from 950 °C and higher, hardness decreased with time, the effect being pronounced at 1000 °C and 1050 °C. These changes are consistent with the resultant microstructural changes. The hardness(H) vs time(t) plots at any temperature are linear and can be represented byH = C1 +C 2t (T °C) The hardnessvs temperature plots as influenced by time, which, in effect, represented how effectively the alloy sustained hardness, are most appropriately represented by a third-order polynomial:H = C1 + C2T+ C3T2 + C4T3 (t s) leading to a horizontal “S” shape. Based on fundamental considerations, the final model interrelating hardness with temperature and time isH = 61.8 e2442.5/T + (0.0188 -1.6 × 10−5·T)t whereT = temperature in K;t = time in seconds; andH = Vickers hardness number, 30 kgf (VHN30). The overall validity and usefulness of the model have been discussed.

Modeling of the corrosion behavior and its interrelation with the deformation behavior and microstructure in a newly developed 7.5Mn-5Cr-1.5Cu alloy white iron

Corrosion rate, (CR), compressive strength (CS), and percent strain were determined for different microstructures generated by heat-treating a newly designed 7.5Mn-5Cr-1.5Cu alloy white iron intended to be used for making castings to resist aqueous corrosion under marine conditions. The microstructures were characterized on the basis of size, shape, and distribution of the second phase, which in the present study comprised dispersed (DCs) and massive carbides (MCs).A new term, “distribution factor” (DF), has been evolved to characterize DCs. This factor proved useful in establishing a relationship between microstructure and CR, which can be represented by the expression CR = [C1 + C2(VMC) + C3(VMC)2] * (DF)4

Secondary hardness of alloy white irons

1. The secondary hardness of chromium white irons is determined by the quantity of residual austenite in the hardened condition and its decomposition in tempering. The optimum austenitizing temperature for the maximum appearance of secondary hardness of chromium white irons is 1100°C, which provides the presence in the hardened specimens of 55–67% residual austenite. 2. The maximum secondary hardness (65–67 HRC) in the widest tempering temperature range (450–550°C) is obtained in irons containing 5–10% Cr and 1–3% Mo.

白鋳鉄の抗折，衝撃試験

Bending and impact tests were carried out on sand-cast specimens and heat-treated ones of C 2∼4.2% white irons and C 3%, Ni 3.5∼4.5%, Cr 1∼2.5 alloy white irons. The results were as follows: (1) Some hair cracks were found in the eutectic cementite or along the boundaries, on the tension side of the bending test pieces, when the tensile strain became about 0.1∼0.5%. (2) When the cracks reached the primary crystals, they passed as transcrystalline (about 70%), or as intercrystalline cracks (about 30%). (3) As the hardness of the primary crystals or C% of the alloys increased, the flexture decreased from 5 to 1 mm, the fracture stress from 160 to 30 kg/mm2, and the impact value from 30 to 10 kg·cm/cm2. (4) The fracture stress in bending tests varied markedly. The factors causing this variation seemed to be S%, C%, the melting, the casting and the heat-treatment conditions of the alloys.

合金白鋳鉄の初晶中のNi Cr濃度

合金白鋳鉄の初晶中のNi Cr濃度

American patents

An investigation has been carried out into the manufacture and field trial of alloy white iron beater plates used to process coal in a KSG coal pulveriser mill. The components were made by the cast bonding process, which involves casting a wear layer onto a steel substrate to form a bimetallic composite product. Four alloy white irons, containing primary and/or eutectic carbide volume fractions ranging from nominally 10 to 40%, were used as the cast overlay in the manufacture of the beater plates. Two replicates of each alloy composition were tested in a mill along with two standard austenitic manganese steel plates. All beater plates completed 3275 h of operation, with the best-performing alloys receiving an additional 3471 h of service in a second campaign. The results showed that increasing carbide volume fraction decreased the wear rate most markedly at sites of low-angle erosion, and that it had a smaller influence at higher angles of abrasive particle attack. Subsequent scanning electron microscopy examination of worn components revealed that the primary mode of material loss at the lower carbide volume fractions was microspalling, with sub-surface fractures occurring within the carbide particles and along carbide-matrix interfaces. Surface microgrooves were more evident in the alloy white iron beater plates with higher carbide volume fractions.