High Chromium White Cast Iron Research Articles

Exploring residual stress analysis in the machining of hypoeutectic high chromium white cast iron alloys through the hole-drilling method

Abstract High chromium white cast irons (HCWCIs), ASTM A352, Type A and Class III, i.e., 25%Cr iron in as-cast condition consists of proeutectic austenite (γ-Fe), transformed martensite (α-Fe) and discontinuous Cr-rich, i.e., M7C3/ (Cr, Fe)7C3 type of carbides, which are hard and brittle in nature. Fully annealed thermal treatment was performed to improve iron’s machinability leading to fully pearlitic matrix with minor retained γ-Fe content. Eutectic (Cr, Fe)7C3 type of carbides are not affected by heat treatment processes. Resulting from corresponding manufacturing process, the magnitude and distribution of residual stresses (RSs) in as-cast and after machining were measured using hole-drilling method (HDM), as they are known to be harmful to corrosion and fatigue resistance. Furthermore, general metallurgical material characterisation was performed in as-cast and heat-treated conditions. As a result, this study revealed hardness variation, 547 and 555BHN in as-cast as compared to 327BHN in heat-treated condition. Furnace and actual cast component chemical analysis revealed a slight variation, especially between carbon (C) and chromium (Cr). Furthermore, eutectic type of carbides and precipitated secondary, i.e., (Cr, Fe)23C6 type of carbides within fully pearlitic matrix with minor amounts of retained γ-Fe were detected within the dominant matrix, i.e., pearlitic matrix in as-annealed condition. Detected magnitude and distributions of RSs on heat-treated sample resulted in higher tensile stresses in the surface and compressive in the interior as compared to sample in as-cast condition. Thus, this study was successfully in measuring RSs in as-cast and upon machining of hypoeutectic irons of HCWCI alloys using HDM.

Effect of Cr:C ratio on open three-body wear resistance of squeeze cast high chromium cast iron

A series of high chromium white cast iron (HCCI) alloys with varying Cr:C ratios were designed and fabricated through the squeeze casting process. This study investigates the effect of the Cr:C ratio on the mechanical properties, microstructure, phase diagram, and both low-stress and high-stress abrasion performance of HCCIs. Alloys with a very high Cr:C ratio exhibited better impact toughness but poorer hardness. Scanning electron microscopy (SEM) and phase diagram calculations elucidated the influence of the Cr:C ratio on microstructure, carbide volume fraction, and carbide type. Abrasion resistance was evaluated using impact abrasive wear (high-stress) and rubber-wheel (low-stress) abrasion on quartzite in open three-body wear. Comprehensive assessments under impact abrasive wear and rubber-wheel abrasive wear conditions suggest that the alloy achieves optimal abrasion resistance with a Cr:C ratio ranging from 8 to 11. Post-wear analysis reveals that surface damage varies between high-stress and low-stress conditions. The microstructure of squeeze HCCIs is significantly influenced by the Cr:C ratio, resulting in diverse operative wear mechanisms, including micro-cutting and micro-fracture. Successful adjustment of the Cr:C ratio led to the attainment of a nearly eutectic HCCIs composition suitable for squeeze casting.

Simulation of the Kinetics of Microstructure Evolution during Destabilization and Tempering of a High-Chromium White Cast Iron

Simulation of the Kinetics of Microstructure Evolution during Destabilization and Tempering of a High-Chromium White Cast Iron

Scouring erosion resistance of metallic materials with composite microstructures

Slurry erosion can cause severe damage and often constitutes a significant portion of the total production cost in many industries such as oil sands and mining. The most commonly used materials for such applications are metallic materials having a composite microstructure consisting of hard reinforcement phases in a more ductile metal matrix. Typical examples are high chromium white irons and tungsten carbide welding overlays. The main purpose of this work is to evaluate the scouring erosion resistance of such materials for applications in handling fine sand slurries and to introduce a wear model to help understand the correlation between erosion resistance and the characteristics of microstructures.Five high chromium white cast irons and four spray and fusion coatings composed of cast tungsten carbide particles and Ni–Cr–B–Si–Fe matrix have been studied using a Coriolis scouring erosion tester in a fine sand slurry. The relationship between the erosion resistance and different microstructure parameters was explored. For the chromium white cast irons, the erosion resistance increased with increase in carbide volume fraction but the spray and fusion coatings showed the opposite trend, i.e., their erosion resistance decreased with increase in the carbide volume fraction. No clear correlation was found between erosion resistance and free path for the spray and fusion coatings while for the chromium white cast irons, the erosion resistance was found to increase rather than decrease with increase in free path.To help explain the experimental results, a wear model has been proposed for the wear resistance of composite microstructures composed of a reinforcement phase (RP) and a metal matrix. In the model, the wear surface of the material is distinguished by four different features/regions, each having unique wear resistance. The rule of mixtures (ROM) for wear resistance is applied to formulate the wear resistance of the material with the above four wear surface features. It is shown that the results can be reasonably well explained based on the proposed model by using the total edge length, L, of the RP particles exposed on a unit area of the wear surface.

Effect of carbide refinement on high temperature erosive wear behavior of high chromium white cast iron with different titanium and carbon additions

It is known that better erosion wear resistance of high chromium (27 wt% Cr) white cast iron (HWCI) with titanium (Ti) addition can be achieved by controlling the size of M7C3 carbides. Nevertheless, it might not be directly applicable to high temperature conditions due to the more complex factors involved, especially the hot oxidation behavior. Therefore, the effect of 0–2 wt% Ti and 3–4 wt% carbon (C) addition on the high temperature erosion wear behavior of HWCI has been investigated in this research. The results show that there are TiC and M7C3 carbides precipitated in the material matrix. The size of M7C3 carbides decreases drastically as the amount of Ti increases. On the contrary, it is effectively enlarged with the addition of higher C. In addition, there is no significant difference in hardness among all specimens due to the relatively similar carbide volume fraction (CVF). The wear resistance of HWCI is improved by increasing the amount of Ti although it has a lower value as the C content increases. It means that hardness is not an important factor in evaluating the wear characteristics of HWCI at high temperatures. The worn surfaces and cross-sections show that the smaller M7C3 carbides are more likely to undergo plastic deformation rather than being directly peeled out. In addition, the effect of hot oxidation behavior was negligible because there is only a very thin oxidation layer on the worn surface. Therefore, it can be concluded that the erosive wear behavior of the material is greatly influenced by the size of M7C3, which the material with better erosive wear resistance contains finer carbides.

Study of the corrosion resistance of high chromium white cast iron welds in the presence of NaOH (30% w/w)

– In the mining industry, specifically in bauxite processing, adverse working conditions demand high mechanical and chemical resistance. For such conditions, the choice of potentially resistant materials, such as high chromium white cast iron (HCr-CWI), is necessary. However, presently, there is no effective recovery of equipment made with HCr-CWI, primarily due to the machining difficulties encountered during the repair process. An alternative recovery method is being developed by the Laboratory of Metallic Materials Characterization at UFPA – LCAM, using electric arc welding with two filler metals: the ER307L stainless steel wire andsa high Mn value wire. Within this context, this study aims to investigate the corrosion resistance of the welded joint obtained with these two filler metals. The base metal (HCr-CWI) was analysed as a reference, alongside the metals generated by the welded joints, ER307L and high Mn. The samples underwent tests involving optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and electrochemical tests for corrosion potential, polarization, and impedance. It was observed that the samples exhibited a similar matrix-carbide structure but with different organization and volumes. However, the electrochemical behaviour in terms of corrosion potential, polarization, and impedance was similar, with very close resultant values: 50 V; 3.53 μA; 0.18 kOhms, respectively. This was supported by the corrosion rate of 0.4mmpy and explained by calculations of Cr and Ni volume, which showed inverse concentration magnitudes among the samples.

Effect of Silica Size on the Relative Wear of Microstructures Containing Solidification Carbides and Tempered Martensite Using a Dry Sand Rubber Wheel Test

The objective of this study was to examine the impact of the size of silica sand particles on the wear resistance of two microstructures containing solidification M7C3 carbides in tempered martensite matrix (namely, AISI D2 steel and high-chromium white cast iron). Wear tests were conducted using abrasive silica sand particles of three different sizes (0.20, 0.50, and 1.0 mm) in a dry sand rubber wheel tribometer (DSRW) following the ASTM G65 standard. Subsequently, these samples were analyzed using microscopy and three-dimensional optical profilometry. The results showed that the wear loss increased with increased abrasive particle size, particularly when the abrasive size increased from 0.5 to 1.0 mm. The microscopic observation revealed silica sand incrustation and plastic deformation of the tempered martensite matrix, cracking of the solidification M7C3 carbides, and detachment of the carbides and matrix. Furthermore, the largest abrasive particle size triggered a more damaging wear mechanism, leading to severe fracture damage of the solidification carbides.

Development and Performance of High Chromium White Cast Irons (HCWCIs) for Wear–Corrosive Environments: A Critical Review

There is a huge demand for high-performance materials in extreme environments involving wear and corrosion. High chromium white cast irons (HCWCIs) display better performance than many materials since they are of sufficient hardness for wear protection and can be tailored in chemical compositions to improve corrosion resistance; however, their performance is often still inadequate. This article reviews the chemical composition and microstructure design aspects employed to tailor and develop HCWCIs with combined corrosion and wear resistance. The performance of these alloys under wear and corrosion is reviewed to highlight the influence of these parameters in the industry. Existing challenges and future opportunities, mainly focusing on metallurgical alloy development aspects like chemical composition, casting, and heat treatment design, are highlighted. This is followed by suggestions for potential developments in HCWCIs to improve the performance of materials in these aggressive environments. Many variables are involved in the design to obtain suitable microstructures and matrix composition for wear–corrosion resistance. Computational modeling is a promising approach for optimizing multi-design variables; however, reliable field performance data of HCWCIs in wear–corrosion environments are still inadequate. Quantitative evaluation of the wear–corrosion performance of HCWCIs requires the development of laboratory and field tests using standard conditions like abrasive type and sizes, severity of loading, slurry velocity, pH, and temperature to develop wear–corrosion maps to guide alloy development.

Heat Treatment Featuring the Key-Parameters of High Chromium White Cast Iron Microstructure

The high chromium white cast iron (HCWCI) has been on the scene for decades, with expectations to remain there due to its exceptional wear resistance. HCWCI is mostly applied as-cast, but it can also be used as a coating material. The carbides in HCWCI microstructure, whose composition depends on alloying and heat treatment regime, give this special feature to white cast irons. The investigation presented in this paper was carried out by examining two HCWCI alloys, denoted HCWCI_1 and HCWCI_2, both alloyed with molybdenum in addition to high chromium content. The HCWCI_1 alloy contains 24.48% Cr with 1.32% Mo, and HCWCI_2 contains 14.11% Cr with 2.47% Mo. Comprehensive qualitative microstructural characterization was performed on all types of samples: as-cast samples, those obtained after quenching (at -196 °C) and/or quenching followed by tempering (at 250 °C). Besides standard etching procedures, the selective color etching was also applied here. The microstructure parameters, such as width of secondary dendritic arms and carbides size, are measured and correlated with applied alloy obtaining procedure and heat treatment regime, so they can be discussed in relation to the microconstituent’s ratio (such as ratio of different carbides) and morphology.

Effects of solidification conditions on the microstructural morphologies and strengths of hypereutectic high-chromium white cast iron castings

Although studies on hypereutectic high-Cr white cast iron (HCWCI) castings have been conducted to improve the toughnesses and quantify the microstructures of these castings, to date, only few studies have been reported on the quantitative influences of solidification conditions on the microstructures and mechanical properties of these castings. Accordingly, herein, the effects of solidification conditions on microstructural morphologies and strengths of hypereutectic HCWCI castings were investigated. Microstructural observation implied positive correlations between the minimum Feret diameter of primary M7C3 and length of M7C3 calculated from a three-dimensional geometric relationship under the approximation of the cylindrical shape of M7C3 and between experimental minimum Feret diameters of primary and eutectic M7C3. Additionally, the experimental minimum Feret diameter of primary M7C3 divided by the cube root of the volume fraction of M7C3 corresponded to the solidification velocity and temperature gradient obtained via solidification simulation. These results indicate that the parameters demonstrating three-dimensional morphologies of primary and eutectic M7C3 can be obtained by solidification simulation. Then, the strengths of the HCWCI castings were evaluated from the rule of mixtures considering the Stroh and Kelly–Tyson equations, where the volume fraction of M7C3 was acquired via thermodynamic calculations according to the chemical compositions of the castings and the strength of the matrix was substituted by the standard strengths of carbon steels under the same C equivalents as that of the matrix. The calculated strength exhibited almost the same magnitude and tendency as those of the experimental strength. The abovementioned findings reveal that not only the microstructural morphologies but also the strengths of the HCWCI castings can be estimated via computer-aided engineering. The results of this study can be utilized to predict the distributions of microstructural morphologies and strengths of the HCWCI castings.

Improving Grinding Ball Lifespan and Efficiency Through Hardenability Modelling and Optimization

Abstract Grinding balls are spherical or cylindrical components used in grinding and milling operations to reduce the size of particles and achieve a finer product. They are made of high chromium white cast iron (HCWCI) and used in a variety of industrial processes. The efficiency of the grinding process is heavily influenced by the properties of the grinding balls, including their composition, size, and hardness. As such, there is ongoing research and development to improve the performance and durability of grinding balls, with the aim of countering the extreme conditions of wear and impact that cause a reduction in their lifespan. This study involved austenitizing balls with diameters of 50 mm and 70 mm at temperatures of 950°C and 1050°C, followed by quenching using both oil and compressed air. By exploiting the experimental HRC hardness results obtained in this work, the study aims to find a mathematical model relating the response (hardenability) to the main effects (austenitization temperature, quenching medium, and diameter balls) and their interactions. Analysis of variance (ANOVA) was used to establish the statistical significance parameters and an optimization of response by the best sub-models method and by the desirability function is realized in the second part of this work. It seems that the austenitization temperature and the size of the balls have a stronger impact on the hardenability of the balls than the cooling rate (quenching medium) by reducing the hardness difference between the surface and the medium of the ball to minimal values.

EFFECT OF BORON ON THE WEAR BEHAVIOR OF HIGH CHROMIUM WHITE CAST IRONS

The wear behavior of high chromium white cast irons with composition: 2,6÷3,4% C; 0,9÷1,1% Si; 0,8÷1,1% Mn; 1,0÷1,3% Mo; 12,3÷13,4% Cr and 0,18 ÷ 1,25% B is investigated. The microstructure and tribological characteristics of six compositions of high chromium white cast irons (one without boron and with 0,18; 0,23; 0,59; 0,96; 1,25% boron) are studied.After casting, heat treatment was carried out, including quenching at 9500C and tempering at 2350C for 1 h. The influence of the heating temperature in the interval 850÷11000С, 25 min on the Rockwell hardness and the microstructure are studied.The wear resistance during abrasive wear for samples after casting and after heat treatment is investigated as measured loss of mass in terms of dry friction under load of 1,5 kg during 10 min. The lowest mass loss during abrasive wear test in dry conditions friction is defined for cast irons alloyed with 0,18 % boron - ∆ m = 0,1469 g after casting and ∆ m = 0,0022 g after heat treatment. The highest mass loss is determined during abrasive testing of alloyed cast irons with 0,96 and 1,25% boron. The alloyed cast irons with 0,18 % boron show highest wear resistance.

Tribological performance of high chromium white cast iron and heat-treated steel used in barite crushing industry

Barite sulfate (BaSO4) is considered a very important mineral material employed as a weighting agent for all types of drilling fluids. Meanwhile, crushers used for the grinding step during barite crushing are affected by catastrophic wear damage located in the hammer parts made from high chromium white cast iron (HCWCI). In the present study, a comparison of the tribological performance between HCWCI and heat-treated steel AISI P20 was conducted to investigate the possible substitution of HCWCI. The tribological test was performed under normal loads between 5 and 10 N for different durations (60, 120, 180, and 240 min). The wear response analysis for both materials showed that the friction coefficient increases as the applied load increases. Moreover, AISI P20 presented the lowest value compared to that attributed to HCWCI in all conditions. Furthermore, the analysis of the wear track obtained by means of scanning electron microscopy (SEM) revealed that the damage was an abrasive wear phenomenon for HCWCI with detection of a crack network throughout the carbide phase, which was more pronounced under the highest load. Regarding AISI P20, an abrasive wear mechanism was detected, characterized by several grooves and ploughing phenomena. Further, the analysis of the wear track using 2D profilometry revealed that for both loads, the maximum wear depth of the HCWCI wear track was significantly greater than that of AISI P20. As a result, when compared to HCWCI, AISI P20 exhibits the best wear resistance. Furthermore, as the load increases, the wear depth and the worn area increase as well. Also, the wear rate analysis supports the previous findings, which showed that under both loads, AISI P20 was more robust than HCWCI.

Investigation and Optimization of Cutting Performance of High Chrome White Cast Iron by Wire Erosion

Investigation and Optimization of Cutting Performance of High Chrome White Cast Iron by Wire Erosion

Effect of Carbon and Titanium Addition on Erosive Wear Behavior of High Chromium White Cast Irons

Effect of Carbon and Titanium Addition on Erosive Wear Behavior of High Chromium White Cast Irons

Study the influence of destabilization and tempering heat treatments on the microstructure of high chromium white cast iron by observing the resulted hardness and Abrasive wear conduct

Study the influence of destabilization and tempering heat treatments on the microstructure of high chromium white cast iron by observing the resulted hardness and Abrasive wear conduct

Effect of Subcritical Treatment (Tempering) on Hardness and Wear of High Chromium White Cast Iron

High chromium white cast iron (HCWCI) is used in mining, crushing plants, as mill liners, and in the manufacture of grinding balls. The grinding ball is the essential element in fine fragmentation. It must have an excellent life to counter extreme wear and impact conditions that it undergoes. Hence it is important to improve its mechanical properties. This study aims to find the effect of tempering temperature on microstructure, hardness, and abrasive wear of High Chromium White Cast Iron used in the manufacture of grinding balls. In this study, the balls in high chromium white cast iron with 12 to 17% Cr, of 50mm and 70mm in diameter were austenitized at 950°C for 45 min and 55 min for the balls of 50 and 70mm then were quenched in forced air. The balls were tempered at 250°C, 400°C, and 600°C for 120 min and 180 min for both diameters 50 and 70mm respectively, and cooled in the furnace. The results showed that tempering practiced at 250°C and 400°C gives an excellent hardness than balls austenitized at 950°C. It is about 60 HRC and it drops to less than 50 HRC for the tempering at 600°C. This tempering causes a significant mass loss (short life) but tempering at 250°C and 400°C decreases this loss by up to 1.6%. The results of XRD showed the presence of the martensite and carbides type M7C3 after tempering at 250°C and a ferritic matrix after tempering at 600°C.

Assessment of the effect of small additions of some rare earth elements on the structure and mechanical properties of castings from hypereutectic chromium white irons

<abstract> <p>Article considers the influence of additions of rare earth elements such as Sm, La, Ce, Nd, and Y on the structure and properties of hypereutectic high-chromium white cast iron of grade G-X300CrMo27-2. To obtain an increased content of carbides in the studied cast iron samples, the carbon content was 3.75–3.9 and 4.1–4.2 wt%. The amount of rare earth elements additives added to the melt is 0.2% by weight. Data were obtained on the effect of overheating and cooling rate in the crystallization interval on the effect of rare earth additives, the structure and properties of white cast iron castings are given. According to the results of the microprobe analysis, it was shown that, under the chosen crystallization conditions, Sm, La, and Ce can form solid solutions with primary and eutectic carbides (FeCr)<sub>7</sub>C<sub>3</sub>. La and Ce form solid solutions with austenite. Nd and Y do not dissolve in iron chromium phases. All listed rare earth elements form phosphides and oxyphosphides. Experimental data are presented on the effect of rare earth elements on the size of primary (FeCr)<sub>7</sub>C<sub>3</sub> carbides and a hypothesis is proposed on the effect of rare earth elements on the crystallization process of hypereutectic chromium white cast irons. Experimental data are presented on the effect of REE additives on the microhardness of phases, hardness, strength, and resistance to abrasive wear of cast iron castings. It was found that the introduction of these additives into hypereutectic chromium white cast iron does not contribute to the modification of the structure and leads to an increase in the size of primary crystals, as well as a decrease in their mechanical properties. However, the addition of Y increases the abrasive wear resistance, but reduces the strength of castings made from such white cast iron.</p> </abstract>

Three-Body Abrasive Wear Performance of High Chromium White Cast Iron with Different Ti and C Content

The need for better wear-resistant materials to reduce cost and save the environment is noteworthy. The striking wear resistance of high chromium white cast iron (HCCI) has made it industry’s predominant choice. The three-body abrasive wear resistance performance of HCCI was investigated based on combined Ti and C. The Ti and C content varied in different percentages. The addition of Ti resulted in refined M7C3 carbides and TiC crystallization. The hardness was significantly affected by the addition of Ti. The increment in Ti content resulted in a decrease in the hardness, leading to a higher wear rate. However, the individual contribution of C led to higher hardness and, hence, better wear resistance, which is contrary to Ti. Out of the three specimens with 3, 3.5, and 4 wt.% C content, the 4 wt.% C series showed the highest hardness but the lowest wear rate and depth. This study found that the combination of a lower percentage of Ti with a higher percentage of C in HCCI can have a worthwhile result in abrasive wear.

Performance Evaluation of High-Chromium White Cast Irons Dual-Reinforced by Niobium Carbides in the Inner Circumference Abrasion Test with Different Abrasive Rock Types

Performance Evaluation of High-Chromium White Cast Irons Dual-Reinforced by Niobium Carbides in the Inner Circumference Abrasion Test with Different Abrasive Rock Types