High Chromium White Cast Iron Research Articles

Effects of pressure and counterbody hardness in the abrasive wear behavior of tool steels

Steels containing up to 1wt% of carbon and 12wt% of chromium have been used to protect the internal surface of rod mills in the cassiterite ore grinding mills. To simulate the wear behavior of this tribosystem, a test rig based on the lapping principle with counterbodies of AISI 1045 steel (160HV30) and a quenched and tempered high chromium white cast iron (751HV30) was selected. The abrasive particles were quartz sand with an average grain size of 150μm. The results showed that using carbon steel as a counterbody and a test pressure of 0.40MPa, the abrasive particles were embedded in the carbon steel leading to a sliding abrasive wear configuration. On the other hand, the use of a hard counterbody of high chromium white cast iron led to much less embedding and the rolling abrasive wear configuration prevailed. Using these parameters, no significant change in the wear rates of the studied steels could be observed. This suggests that the chromium content may be strongly reduced, and consequently the maintenance cost of this kind of mills.

The influence of manganese for structure of high-chromium white cast iron

Results of researches of manganese influence on of structure and hardness of high-chromium white cast iron are presented.

The Role of Silicon in the Solidification of High-Cr Cast Irons

This work analyzes the effect of different additions of silicon (0 to 5.0 pct) on the structure of a high-Chromium white cast iron, with chromium content of 16.8 pct and carbon 2.56 pct. The alloys were analyzed in both as-cast and heat-treated conditions. Casting was undertaken in metallic molds that yielded solidification rates faster than in commercial processes. Nevertheless, there was some degree of segregation of silicon; this segregation resulted in a refinement in the microstructure of the alloy. Silicon also generated a greater influence on the structure by destabilizing the austenitic matrix, and promoted greater precipitation of eutectic carbides. Above 3 pct silicon, pearlite formation occurred in preference to martensite. After the destabilization heat treatment, the matrix structure of the irons up to 3 pct Si consisted of secondary carbides in a martensitic matrix with some retained austenite; higher Si additions produced a ferritic matrix. The different as-cast and heat-treated microstructures were correlated with selected mechanical properties such as hardness, matrix microhardness, and fracture toughness. Silicon additions increased matrix microhardness in the as-cast conditions, but the opposite phenomenon occurred in the heat-treated conditions. Microhardness decreased as silicon content was increased. Bulk hardness showed the same behavior. Fracture toughness was observed to increase up to 2 pct Si, and then decreased for higher silicon contents. These results are discussed in terms of the effect of eutectic carbides’ size and the resulting matrix due to the silicon additions.

Correlation among abrasive wear tests

ABSTRACTThe study of wear is generally focused on reproducing micromechanisms that are identified on industrial applications in the laboratory. To do so, many tribometers have been developed, but not much attention has been given to the correlation among the variety of abrasive test results. This study aims to compare four different abrasive wear tests: pin‐on‐disc, single pass pendulum, linear scratch and the laboratory of tribology and materials test. High chromium white cast irons were tested in different conditions. It was observed that the wear resistance classification offered by the pendulum scratch and the laboratory of tribology and materials test was the same and was the opposite of the classification offered by the scratch and pin‐on‐disc tests. The wear rate behaviour verifies the existing constant depth and constant load models regarding the force transferred to the contact region. For the latter, the wear behaviour is better explained by the product k*q, parameters that are obtained from the pendulum test. Copyright © 2012 John Wiley & Sons, Ltd.

Microstructural study of surface melted and chromium surface alloyed ductile iron

In this study, ductile iron was surface melted and chromium surface alloyed via pre-placing of ferrochromium powder with different thicknesses and subsequently surface melting by tungsten inert gas (TIG) process. Optical and scanning electron microscopy, as well as micro-hardness testing and X-ray diffraction analysis were used for characterization of the treated samples. Surface melting and chromium surface alloying resulted in formation of ledeburitic structure and high chromium white cast iron in the treated layers, respectively. It was also noticed that hardness of the treated layers was considerably higher than that of the base material. Increasing thickness of ferrochromium layer increased the amount of M7C3 carbides and hardness of the alloyed layer.

Microstructures and Mechanical Properties of Austempered Fe-C-Si-B Alloy

A new type of Fe-C-Si-B alloy was developed. The investigation on microstructure details and the mechanical properties were performed for different austempering combinations. The results indicated that the Fe-C-Si-B alloy comprises ferrite, pearlite and interdendritic eutectic borides in as-cast condition. The distribution of eutectic boride with a chemical formula of M2B (M represents Cr, Fe, Mn or Mo) and is much like that of carbide in high chromium white cast iron. Pure ausferrite structure that is consisted of bainitic ferrite and carbon-riched retained austenite can be obtained by austempering treatment to the Fe-C-Si-B alloy. No carbide would precipitate in the structure and there is not any morphology change of borides. The hardness of the Fe-C-Si-B alloy decreases with increasing of the austempering temperature, and decreases greatly in at the early stages (within 5 to 10 min) of austempering transformation. The transformation is almost finished after about 5 to 10 min when thehardness of the alloy does not change anymore. The Fe-C-Si-B alloy is a new kind of wear resistance material with bright application prospect.

Chemical Composition and Morphology of M7C3 Eutectic Carbide in High Chromium White Cast Iron Alloyed with Vanadium

The chemical composition and morphology of M7C3 eutectic carbides in 19 mass% Cr–2.8 mass% C white iron with up to 4.7 mass% V additions have been studied. Eutectic colonies are mainly composed of a very fine rod-like carbides at the center and become coarser rod-like or blade-like with increased distance from the center. The volume fraction, size and distribution of rod-like and blade-like carbides in the eutectic colonies are changing with increasing vanadium content in the alloys. The formation of the eutectic colonies of different morphology is the consequence of the segregation of alloying elements in the alloy melt, which was confirmed by EDS analysis of the chemical composition of carbides. Three different compositions of M7C3 carbides were found in all tested alloys. The main difference between them is in the amount of chromium and iron and in the degree of their replacement by vanadium. Due to different melt composition in particular zones, the constitutional undercooling, and subsequently the growth rate, will be different, which will induce the formation of eutectic colonies of different morphologies.

Investigations on Microstructures and Two-body Abrasive Wear Behavior of Fe–B Cast Alloy

The microstructures of Fe–B alloys containing different carbon and boron concentrations have been investigated. The solidification microstructures of Fe–B alloy consist of the eutectic boride, pearlite, and ferrite. Borides precipitate along the grain boundary during the formation of eutectic. After heat treatment, the phases in Fe–B alloy are composed of the boride and martensite. With increase of carbon and boron concentrations, the Rockwell hardness of Fe–B alloy becomes larger. Meanwhile, by using a pin-on-disk abrasion tester, the effects of carbon and boron concentrations on the wear behaviors including ploughing depth, roughness, and wear weight loss under different loads have been studied. The results show that the wear resistance of Fe–B alloy with higher carbon and boron concentrations is comparable with the high chromium white cast iron.

Effect of exposure time on the morphology of corrosion on high chromium white cast iron in high temperature caustic solutions

AbstractHigh chromium white irons are important candidate materials for use in alumina refineries to combat wear and corrosion. The effect of exposure time on the formation of oxide films was studied in a 23% Cr white cast iron exposed at 260 °C in 110 g/l caustic soda solutions. It was found that whilst well‐formed octahedral M(II)O.M(III)2O3 spinel type oxides initially formed and spread across the surface of the material, these were gradually replaced by a background oxide with a higher Cr/Fe ratio and the morphology of the octahedral crystals became less well formed. Also, the oxidation was found to be predominantly in the matrix material, leaving carbide particles unsupported on the surface and in the later stages, significant corrosion was found along the carbide/matrix phase boundary.

Structural changes have in complex alloying white iron during destabilizing heating

The data concerning the kinetics of secondary carbides precipitation and hardness of high-chromium white cast iron during destabilization are presented.

Microstructure and properties of hypereutectic high chromium white cast iron prepared under pressure

In this paper, a semisolid slurry of hypereutectic high chromium cast iron (HCCI) was prepared in a metal mould by a cooling slope body method under pressure. The results indicated that the size of the primary carbide in the semisolid hypereutectic HCCI specimens becomes much finer, and there is no shrinkage porosity in the semisolid microstructure under a pressure of 150 MPa. The impact toughness of a semisolid specimen without shrinkage porosity is increased by about 121 and 17% compared with those of conventional and semisolid specimens with shrinkage porosity respectively. Furthermore, using SiC particles of 80–100 mesh in size as abrasives, the wear resistance of semisolid specimens without shrinkage porosity is increased by about 78 and 20% compared with those of conventional and semisolid specimens with shrinkage porosity respectively.

An experimental study of laser-assisted machining of hard-to-wear white cast iron

Laser-assisted machining has been considered as an alternative for hard-to-wear materials such as metallic alloys and ceramics. Machining of some materials such as high chromium alloys and high strength steels is still a delicate and challenging task and has received little attention. Conventional computer numerical control machines and cutting tools cannot adapt easily to such materials and induce very high tooling costs for operations of rough machining or finishing. This paper presents the results of research conducted on laser-assisted machining of one such hard-to-wear materials, high chromium white cast iron, used in making heavy duty mineral processing equipment for the mining industry. In particular, the effect of laser on temperature, cutting forces, surface profile, hardness and cutting chips are presented. Results show that laser-assisted machining causes more frequent shearing of material, less uniform surface formation, and the heat penetration increases as the distance between laser spot and tool increases. It also leads to reduction in cutting forces with expected improvement in tool life. The results indicate that laser-assisted machining of high chromium white cast iron shows potential to be a feasible alternative to hard machining of such materials.

High Temperature Oxidation of High Chromium White Cast Iron

High Temperature Oxidation of High Chromium White Cast Iron

High Temperature Compressive Strength of High Chromium White Cast Irons

High Temperature Compressive Strength of High Chromium White Cast Irons

Joining of High Chromium White Cast Irons to Ceramics by Using Active Filler Metal and Aluminum

Joining of High Chromium White Cast Irons to Ceramics by Using Active Filler Metal and Aluminum

Decomposition Behavior of Retained Austenite of High Chromium White Cast Iron

Decomposition Behavior of Retained Austenite of High Chromium White Cast Iron

The Role of Manganese on Microstructure of High Chromium White Cast Iron

To determine the effect of austenite stabilizer element on the microstructure and behaviour of as–cast high Cr white cast iron Fe-21Cr-3Ni-1.7Mo-2.4C, different percentages of Mn (0.4, 0.9, 1.3, 1.7, 2.2 and 2.6 wt%) were added. Detailed investigations were carried out using scanning electron microscopy, energy dispersive spectroscopy analysis (EDS), X-ray diffraction and hardness test. It showed that with increasing Mn addition, the austenite phase (γ) of the as-cast alloys refine clearly. The morphology of the austenite phase for all alloys is a mixture of dendrite and plate like. The austenite phase refines clearly with increasing manganese addition. The major carbide phase formed in the as- cast alloys is M7C3 with minor carbides of (Fe,Cr)23C6 and Mo2C. Microstructure analysis showed the presence of small amounts of martensite and delta ferrite in all as-cast alloys. The hardness was decreased continuously with increasing Mn content. This is mainly attributed to the morphology of carbides rather than to small variation in carbides content. It was observed that considerable amounts of Mn were found in the carbides lower than that in the austenite matrix.

Abrasion wear behaviour of alloyed and chilled cast irons

Abstract High-chromium white cast irons are widely used in a variety of applications that require high wear resistance. This outstanding performance is due to the presence of large amounts of chromium carbides which exhibit high hardness. However, for wear-resistant applications exposed to impact, ductile cast iron is a candidate material due to its good wear behaviour, reduced brittleness and lower production costs. That is the case of the working rolls employed in clay mass rolling operations which operate under significant wear conditions and impacts (due to foreign bodies mixed in the ceramic mass). In the present study, the effect of the chemical composition on microstructure and abrasion wear of two high-chromium white cast irons (13% Cr and 19% Cr) and a chilled ductile cast iron with 0.6% Cr was investigated. The microstructural characteristics and hardness were evaluated and correlated with the wear data. Ball cratering tests, using abrasive slurry containing SiC particles, were carried out to rank the abrasive wear resistance of the alloys, in the as-cast condition, obtained by permanent mould casting. The alloy with the highest chromium content (and higher ratio Cr/C = 6.8) presents a larger volume fraction of chromium-richer carbides providing better wear resistance. Ductile iron exhibits good wear performance in the chilled region due to a fine abrasion-resistant carbide network.

Solidification of High Chromium White Cast Iron Alloyed with Vanadium

Experimental results indicate that vanadium affects the solidification process in high chromium iron. Vanadium is distributed between eutectic M7C3 carbide and the matrix, but its content in carbide is considerably higher. Also, this element forms vanadium carbide. TEM observation reveals that vanadium carbide present in examined Fe-Cr-C-V alloys is being of M6C5 type. DTA analysis found that with increasing vanadium content in tested alloys, liquidus temperature is decreasing, while eutectic temperature is increasing, i.e. the solidification temperature interval reduces. The narrowing of the solidification temperature interval and the formation of larger amount of vanadium carbides, as a result of the increase in the vanadium content of the alloy, will favour the appearance of a finer structure. In addition, the phases volume fraction will change, i.e. the primary γ-phase fraction will decrease and the amount of M7C3 carbide will increase.

Microstructure and Properties of Isothermally Quenched High Boron White Cast Iron

Microstructure and properties of isothermally quenched high boron white cast iron were investigated in this paper. The results show that the microstructure of high boron white cast iron is mainly composed of many continuous and netlike eutectic borides, pearlite and ferrite under as-cast condition. The microhardness of Fe2B ranges in 1200-1600HV whose value seems to approximate that of (Fe,Cr)7C3–type carbide (HV1200~1800) in high chromium white cast iron. After isothermal quenching, the matrix transforms into lower bainite in which carbide precipitations are arranged in parallel rows at an angle of 60 deg to the long axis of the plates, but the morphology of boride remains nearly unchanged compared with its as-cast condition. Moreover, precipitation particles with the size of about 1~4 μm can be found in the matrix of isothermally quenched high boron white cast iron. Impact fracture morphology of isothermally quenched high boron white cast iron indicates that fracture propagated more easily through boride/matrix interface than through matrix.