Erosive Wear Resistance Regarding Different Destabilization Heat Treatments of Austenite in High Chromium White Cast Iron, Alloyed with Mo

With the aim of improving erosive wear resistance in hypoeutectic white cast irons with 18% Cr and 2% Mo, several samples of this grade were subjected to different heat treatments at 1000 °C to destabilize the austenite. The dwell times at this temperature varied from 4 to 24 h and the samples were cooled in air or oil. The existing phases were identified and quantified by applying the Rietveld structural refinement method. The results were correlated with the hardness of the material and with the microhardness of the matrix constituent. The greatest resistance to erosive wear was achieved in those samples that had a higher percentage of secondary carbides. The longer the dwell time at the destabilization temperature of austenite, the greater the amount of precipitated secondary carbides. However, the percentage of dissolved eutectic carbides is also higher. These eutectic carbides were formed as a result of non-equilibrium solidification. Low cooling rates (in still air) can offset this solution of eutectic carbides via the additional precipitation of secondary carbides in the 600–400 °C temperature range. A sharp decrease is observed in the percentage of retained austenite in those treatments with dwell times at 1000 °C equal to or greater than 12 h, reaching minimum values of around 2% volume. The percentage of retained austenite was always lower after oil quenching and the hardness of oil quenched samples was observed to be greater than those quenched in air. In these samples, the maximum hardness value obtained was 993 HV after a 12 h dwell, which result from the optimum balance between the percentages of retained austenite and of precipitated carbides.

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Influence of Thermal Parameters Related to Destabilization Treatments on Erosive Wear Resistance and Microstructural Variation of White Cast Iron Containing 18% Cr. Application of Design of Experiments and Rietveld Structural Analysis

Materials ◽

10.3390/ma12193252 ◽

2019 ◽

Vol 12 (19) ◽

pp. 3252 ◽

Cited By ~ 4

Author(s):

Alejandro Gonzalez-Pociño ◽

Florentino Alvarez-Antolin ◽

Juan Asensio-Lozano

Keyword(s):

Wear Resistance ◽

Design Of Experiments ◽

Retained Austenite ◽

Erosive Wear ◽

Structural Refinement ◽

Cast Irons ◽

Additional Increase ◽

Eutectic Carbides ◽

The Matrix ◽

Key Factor

High-Cr hypo-eutectic white cast irons are used in very demanding environments that require high resistance to erosive wear. The influence on the microstructural variation and erosive wear resistance of several fundamental factors related to the thermal treatments of these cast irons was analysed by means of a fractional Design of Experiments (DoE). These factors included the ones related to the destabilization of austenite. The precipitated phases were identified by X-ray diffraction (XRD), while the Rietveld structural refinement method was used to determine their percentages by weight. Erosion wear resistance was calculated using the test defined by ASTM G76. It was concluded that the quench cooling medium does not significantly influence either erosive wear resistance or the proportion of martensite or retained austenite. The destabilization temperature is a key factor with respect to the percentage of retained austenite. In order to increase the amount of martensite and decrease the amount of retained austenite, temperatures not exceeding 1000 °C are required. An increase of 100 °C in the destabilization temperature can lead to a 25% increase in retained austenite. Moreover, tempering temperatures of around 500 °C favour an additional increase in the percentage of martensite. Erosive wear commences on the matrix constituent without initially affecting the eutectic carbides. Once the deterioration of the matrix constituent surrounding these carbides occurs, they are released. High tempering times provide an increase in resistance to erosive wear due to a second destabilization of austenite during the said tempering.

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Optimization of Thermal Processes Applied to Hypoeutectic White Cast Iron containing 25% Cr Aimed at Increasing Erosive Wear Resistance

Metals ◽

10.3390/met10030359 ◽

2020 ◽

Vol 10 (3) ◽

pp. 359 ◽

Cited By ~ 3

Author(s):

Alejandro Gonzalez-Pociño ◽

Florentino Alvarez-Antolin ◽

Juan Asensio-Lozano

Keyword(s):

Wear Resistance ◽

Erosive Wear ◽

Decisive Role ◽

Standard Test ◽

Test Method ◽

Structural Refinement ◽

Cast Irons ◽

Eutectic Carbides ◽

The Matrix ◽

Tempering Treatment

Hypoeutectic white cast irons containing 25% Cr are used in very demanding environments that require high resistance to erosive wear, for instance, the crushing and processing of minerals or the manufacture of cement. This high percentage in Cr, in turn, favors corrosion resistance. The application of a Design of Experiments (DoE) allows the analysis of the effects of modifying certain factors related to the heat treatments applied to these alloys. Among these factors, the influence of prior softening treatment to facilitate the machining of these cast irons and the influence of the factors related to the destabilization of austenite, during both quenching and tempering, were analyzed. The precipitated phases were identified by X-ray diffraction (XRD), while the Rietveld structural refinement method was used to determine their percentages by weight. Erosive wear resistance was calculated using the ASTM G76 standard test method. It is concluded that the thermal softening treatment, consisting of 2 h at 1000 °C and 24 h at 700 °C, does not result in additional softening of the material compared to its as-cast state. Furthermore, it is observed that not only eutectic carbides influence wear resistance, but that the influence of the matrix constituent is also significant. It is also verified that the tempering treatment plays a decisive role in wear resistance. Temperatures of 500 °C and tempering times of 6 h increase the wear resistance and hardness of the aforementioned matrix constituent. Tempering temperatures of 200 °C lead to an increase in retained austenite content and the presence of M3C carbides versus mixed M7C3 and M23C6 carbides. The quench cooling medium is not found to have a significant influence on the hardness or wear resistance.

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The Joint Effects of Nitriding and Parameters Related to the Destabilisation of Austenite on Wear Resistance in White Cast Iron with 25% Cr

Metals ◽

10.3390/met11010085 ◽

2021 ◽

Vol 11 (1) ◽

pp. 85

Author(s):

Alejandro González-Pociño ◽

Florentino Alvarez-Antolin ◽

Juan Asensio-Lozano

Keyword(s):

Wear Resistance ◽

Cast Iron ◽

White Cast Iron ◽

Nitrided Layer ◽

Erosive Wear ◽

Air Cooling ◽

Cast Irons ◽

Eutectic Carbides ◽

Noticeable Increase ◽

Ionic Nitriding

In this article, the effects of an ionic nitriding treatment are analysed, together with deliberate variation of different thermal parameters associated with the destabilisation of austenite, on erosive wear resistance of white cast irons with 25% Cr. The methodology followed in this research was an experimental design, where six factors were analyzed by performing eight experiments. The thickness of the nitrided layer is much smaller than in white cast iron with lower percentages in Cr, never reaching 20 microns. The nitriding treatment entails considerable softening of the material underneath the nitriding layer. This softening behaviour becomes partially inhibited when the destabilisation temperature of austenite is 1100 °C and dwell times at such temperature are prolonged. This temperature seems to play a significant role in the solubilization of non-equilibrium eutectic carbides, formed during industrial solidification. The nitriding treatment leads to additional hardening, which, in these cases, favours a second destabilisation of austenite, with additional precipitation of secondary carbides and the transformation of retained austenite into martensite. Despite softening of the material, the nitriding treatment, together with air-cooling after destabilisation of the austenite, allows a noticeable increase in resistance to erosive wear.

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Improvement of Impact Toughness and Abrasion Resistance of a 3C-25Cr-0.5Mo Alloy Using a Design of Experiment Statistical Technique: Microstructural Correlations after Heat Treatments

Metals ◽

10.3390/met11040595 ◽

2021 ◽

Vol 11 (4) ◽

pp. 595

Author(s):

Alejandro González-Pociño ◽

Juan Asensio-Lozano ◽

Florentino Álvarez-Antolín ◽

Ana García-Diez

Keyword(s):

Wear Resistance ◽

Impact Toughness ◽

Abrasive Wear ◽

Design Of Experiment ◽

Retained Austenite ◽

Statistical Technique ◽

Cast Irons ◽

Slow Cooling ◽

Tempering Temperature ◽

The Matrix

Hypoeutectic high chromium white cast irons are commonly used in the mining and cement industries, where high resistance to abrasive wear is demanded. Through the application of a Design of Experiment technique (DoE), different factors related to thermal industrial treatments are analysed with regard to resistance to abrasive wear and impact response. Abrasion tests were carried out in accordance with the ASTM G065-16 standard. The provisional results show that to increase wear resistance, high destabilisation temperatures (1050 °C) followed by slow cooling to room temperature (RT) and subsequent tempering at 400 °C are most favourable. This is because these conditions are favourable to maintaining a certain tetragonality of the martensite after tempering and also, because of the presence of a high density of mixed carbides M7C3, through a secondary precipitation during cooling. Oil quenching and a high tempering temperature (550 °C) with long dwell times of 6 h were found to increase impact toughness. These conditions favour a lack of retained austenite. The presence of retained austenite was found unfavourable for both wear resistance and toughness, whereas tempering at 400 °C has been shown to be insufficient to transform martensite on tempering, which in turn seemed to increase the hardness of the matrix constituent.

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Influence of Ni Content on Erosive Wear and Destabilization Heat Treatment Conditions Behavior of Multi Component White Cast Iron

Materials Science Forum ◽

10.4028/www.scientific.net/msf.998.48 ◽

2020 ◽

Vol 998 ◽

pp. 48-54

Author(s):

Kenta Kusumoto ◽

Kazumichi Shimizu

Keyword(s):

Heat Treatment ◽

Wear Resistance ◽

Cast Iron ◽

White Cast Iron ◽

Erosive Wear ◽

Wear Property ◽

Eutectic Carbides ◽

Secondary Carbides ◽

Ni Content ◽

Ni Addition

This study investigated the influence of nickel (Ni) addition on erosive wear property of multi-component white cast iron with good erosive wear resistance. Multi-component white cast irons (MWCIs) with 2 mass % of carbon (C), 5 mass % of chromium (Cr), molybdenum (Mo), tungsten (W), niobium (Nb) and 0, 3, 5 mass % of Ni were prepared as experimental materials. The heat treatment condition was quenching by forced air cooling after keeping the specimens at 1123K for 3.6ks. Specimens with size of 50mm×50mm×10mm were tested using a suction-type blasting machine. The test was conducted with impact angle of 30, 60 and 90 deg. at room temperature. Collision particles were irregular steel grids with average particle diameter of 770μm and hardness of 810HV1. The speed of air flow was about 100m/s while the speed of impact particles was around 20.0g/s and the total time of each experiment was 3600 sec.. According to the result, erosion rate was decreased with the increase of Ni content in all of the impact angles. Especially, MWCIs which contain 5 mass % Ni showed the most excellent erosive wear resistance. As reasons, it can be considered that with Ni addition, the volume fraction of eutectic carbides and secondary carbides was increased which enhanced the matrix structure and suppressed the surface deformation of the experimental surface. Therefore, the increasing of eutectic carbides and secondary carbides can be considered as the reason of erosive wear resistance increased.

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Heat Treatments of Chromium-Manganese White Cast Irons for an Optimum Combination of Wear Resistance and Impact Strength

MRS Proceedings ◽

10.1557/proc-34-537 ◽

1984 ◽

Vol 34 ◽

Author(s):

A. Basak ◽

J. Penning ◽

J. Dilewijns

Keyword(s):

Wear Resistance ◽

Cast Iron ◽

Impact Strength ◽

White Cast Iron ◽

Heat Treatments ◽

Optimum Combination ◽

Austenitic Matrix ◽

Cast Irons ◽

Martensitic Matrix ◽

Eutectic Carbides

As cast microstructures of chromium-manganese white cast iron containing about 2.5 % carbon, 0.7 % silicon, 4.5 % manganese and 11.5 % chromium reveal discontinuous plate like eutectic carbides embedded in a mainly austenitic matrix[1](Fig.1). This austenitic matrix accounts for a higher impact strength and a lower wear resistance. It has been reported elsewhere [2] that a martensitic matrix containing uniformly distributed fine alloy carbides exhibits a very good wear resistance, but lower impact strength.

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Iron-chromium-carbon-vanadium white cast irons: Microstructure and properties

Hemijska industrija ◽

10.2298/hemind130615064f ◽

2014 ◽

Vol 68 (4) ◽

pp. 413-427 ◽

Cited By ~ 16

Author(s):

Mirjana Filipovic

Keyword(s):

Fracture Toughness ◽

Strain Hardening ◽

Volume Fraction ◽

Dynamic Fracture Toughness ◽

M23c6 Carbide ◽

Cast Irons ◽

Repeated Impact ◽

Secondary Carbides ◽

The Matrix ◽

Microstructure Parameters

The as-cast microstructure of Fe-Cr-C-V white irons consists of M7C3 and vanadium rich M6C5 carbides in austenitic matrix. Vanadium changed the microstructure parameters of phase present in the structure of these alloys, including volume fraction, size and morphology. The degree of martensitic transformation also depended on the content of vanadium in the alloy. The volume fraction of the carbide phase, carbide size and distribution has an important influence on the wear resistance of Fe-Cr-C-V white irons under low-stress abrasion conditions. However, the dynamic fracture toughness of Fe-Cr-C-V irons is determined mainly by the properties of the matrix. The austenite is more effective in this respect than martensite. Since the austenite in these alloys contained very fine M23C6 carbide particles, higher fracture toughness was attributed to a strengthening of the austenite during fracture. Besides, the secondary carbides which precipitate in the matrix regions also influence the abrasion behaviour. By increasing the matrix strength through a dispersion hardening effect, the fine secondary carbides can increase the mechanical support of the carbides. Deformation and appropriate strain hardening occur in the retained austenite of Fe-Cr-C-V alloys under repeated impact loading. The particles of precipitated M23C6 secondary carbides disturb dislocations movement and contribute to increase the effects of strain hardening in Fe-Cr-C-V white irons.

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Structural Investigations of Solidification and Heat Treatments Influence on High Alloyed Cast Irons Grades with Nb-V-Ti Additions

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.289-292.77 ◽

2009 ◽

Vol 289-292 ◽

pp. 77-86 ◽

Cited By ~ 4

Author(s):

Jacqueline Lecomte-Beckers ◽

Jérôme Tchoufang Tchuindjang

Keyword(s):

Phase Transformations ◽

Volume Fraction ◽

Raw Materials ◽

Solidification Process ◽

Heat Treatments ◽

Hot Strip Mill ◽

Cast Irons ◽

Structural Investigations ◽

Alloyed Cast ◽

The Matrix

Two High Alloyed Cast Irons (HACI) were studied, both belonging to the Fe-C-Cr-Si-X system where X represented a strong carbide forming element. One of these alloys was obtained after adding Nb, V and Ti to the chemical composition of the other alloy. Raw materials originated from spun cast rolls for hot strip mill were submitted to different heat treatments routes, in order to study the influence of alloying elements on the microstructure. Both HACI grades contained a mixture of martensite and retained austenite matrix in the as-cast conditions and after quenching. Differential Thermal Analysis was carried out on the heat treated samples in order to determine the phase transformations occurring during re-melting and subsequent solidification sequence. Diffusionless transformations leading to various types of martensite were found in the matrix. Bulky NbC carbides precipitating at the beginning of the solidification process strongly influence the nature and the rate of the subsequent diffusional phase transformations, particularly for HACI grade with Nb, V and Ti additions. Quantitative metallography was done to determine graphite, NbC carbides, cementite and matrix volume fraction in HACI studied grades.

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Study of the Origin of the Unexpected Pearlite during the Cooling Stage of Two Cast High-Speed Steels

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.172-174.803 ◽

2011 ◽

Vol 172-174 ◽

pp. 803-808 ◽

Cited By ~ 2

Author(s):

Jérôme Tchoufang Tchuindjang ◽

Jacqueline Lecomte-Beckers

Keyword(s):

Retained Austenite ◽

High Speed ◽

Solid Phase ◽

Casting Process ◽

Eutectic Phase ◽

Chemical Compositions ◽

Spin Casting ◽

Eutectic Carbides ◽

Similar Chemical ◽

The Matrix

Two HSS grades (A and B) belonging to the complex system Fe-Cr-C-Si-X, where X is a strong carbide-forming element such as V, Mb or W, were studied. Samples in the as-received conditions came from an industrial spin casting process, with a varying cooling rate during processing. Chemical compositions of both alloys were closed to each other and were chosen to enhance their hardenability and to avoid less resistant phases such as pearlite and ferrite. Differential Thermal Analysis was performed on both alloys, in order to increase their crystallization behaviour. Light microscopy and SEM associated with EDS analyses were done to characterize the microstructure of both alloys in the as-received conditions and after DTA trials. The matrix of both HSS grades was composed of eutectic carbides, martensite and retained austenite, these phases exhibiting similar chemical compositions in both alloys. Unexpected pearlite was found in the as-cast HSS alloy B without W, this grade containing more Mo, more V and less Cr than the HSS grade A. It appeared from DTA tests that pearlite found in the alloy B arose more from the destabilisation of the Cr-rich retained austenite associated with the plate-like M2C carbide, than from the matrix itself. In fact, pearlite zones located in the vicinity of M2C are due to related isothermal solid phase transformations form the previous austenitic eutectic phase that is enriched with Cr and Mo.

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Structure and Properties of Cast Iron DESIGNATED for Working Layer of Rolls

Journal of Materials Science Research ◽

10.5539/jmsr.v5n1p77 ◽

2015 ◽

Vol 5 (1) ◽

pp. 77 ◽

Cited By ~ 1

Author(s):

K. N. Vdovin ◽

A. N. Zavalishchin ◽

D. A. Gorlenko ◽

N. A. Feoktistov

Keyword(s):

Cast Iron ◽

Retained Austenite ◽

Volume Fraction ◽

Centrifugal Casting ◽

Structure And Properties ◽

Cast Irons ◽

Metallic Base ◽

Slow Cooling ◽

Working Layer ◽

Secondary Carbides

The formation of the structure and properties of cast irons designated for the working layer during solidification and subsequent tempering of Indefinite Chill Double Poured Centrifugal Casting Rolls (ICDP) has been studied.Graphitization of cast irons designated for the working layer of rolls occurs under isothermal conditions at high temperatures, which vary over the cross section and resulted from casting the roll core. At subsequent slow cooling, secondary carbides precipitate and austenite partially transforms into martensite; the resulting end structure consists of martensite and austenite metallic base (primary austenite dendrites) with 11.4 per cent of retained austenite, 26 per cent of eutectic and secondary carbides, and 2.6 per cent of flake graphite. The amount of retained austenite in the metallic base of the cast structure of cast iron designated for the working layer, heated to 430 °C, decreases from 11.4 per cent to 3.2 per cent due to the partial transformation into bainite. The martensite tetragonality decreases due to the carbide precipitation; the existing excess phases grow and the new ones are formed; the total volume fraction of the carbide phase increases to 29.8 per cent and graphite to 3.7 per cent.

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