7C3 Carbides Research Articles

Fe-based metallic glass coatings with suppressed cracks and enhanced wear resistance prepared by extreme high-speed laser cladding

Fe-based metallic glass (MG) coatings draw great attentions due to their excellent wear resistance. The recently developed extreme high-speed laser cladding (EHLC) provides a promising method for their fabrication but limited by the strong tendency to crack. Besides that, the deep insight into the structure evolution and the failure mechanism of the coating is still lacked. Thus, the understanding of the crack origin and the prevention of crack are of great importance. In the present work, Fe-Mo-Cr-Y-C-B MG coatings with adjustable glassy phase content were successfully fabricated by EHLC. The microstructure characterization of the coatings reveals that the cracks is main caused by the hard and brittle nanocrystalline phases precipitations of monoclinic Mo12Fe22C10 and (Fe, Cr)23C6 carbides in the heat affected zone. Therefore, the cracking of the coatings can be effectively reduced by increasing the glassy phase content. Subsequently, the hardness distribution, wear performance and wear mechanism of the coatings were investigated. The results showed that increasing the glassy phase content can effectively achieve low wear rate. The prepared Fe-Mo-Cr-Y-C-B MG coatings exhibit abrasion loss as low as 3.54·10−6 mm3 (N m)−1, which is an order of magnitude lower than that of the 45# steel substrate. The wear of the coatings is primarily attributed to the fatigue wear accompanied with slighting oxidative wear. By suppressing the brittle precipitated crystalline phases in the coating, the fatigue wear can be reduced and the wear resistance of the coatings can be improved. The present work provides insights into the crack prevention and were performance improvement of the Fe-based MG coatings prepared by EHLC.

Strength stability at high temperatures for additively manufactured alumina forming austenitic alloy

Several fast-spectrum nuclear reactors designed to generate high power (∼450 MWe) rely on forced convection of media such as supercritical CO2, sodium, or liquid lead to cool the nuclear core, operating at temperatures up to 600 °C. Cost-effective, high-strength Fe-based alumina forming austenitic (AFA) alloys are a promising candidate for the fabrication of critical nuclear components. This study investigated laser powder bed fusion (LPBF) processing of an AFA alloy composition optimized for improved creep resistance. Electron microscopy revealed an elongated grain structure along the build direction with a fine sub-grain cellular structure decorated with (Cr,Fe,Nb)23C6 carbide precipitates at the intercellular boundaries. At temperatures of 20–900 °C, the LPBF alloy's superior tensile properties compared to its arc-melted counterpart and other advanced steels (e.g., SS316) were attributed to the distribution of nano-sized carbide precipitates, whereas the high ductility was attributed to the LPBF alloy's elongated grain structure.

Effect of steel matrix with different C content on the growth mechanism, microstructure and properties of the chromized layer

The C content of the steel matrix has significant influence on the growth mechanism, microstructure and properties of the chromized layer. However, the relevant research literature is scarce. In this paper, seven kinds of low carbon alloy steels with C content ranging from 0.08 wt% to 0.45 wt% were selected as matrix for chromizing experiments under the same parameters. The effects of matrix C content on the growth mechanism, growth rate, structure and properties of the chromized layer were discussed. The results show that the chromized layer is composed of outer porous (Cr, Fe)23C6 and (Cr, Fe)7C3 carbides layer and inner dense FeCr phase layer for matrix with C content lower than or equal to 0.2 wt%. While when the matrix C content is >0.2 wt%, the chromized layer becomes three-layer structure: the surface (Cr, Fe)23C6 phase layer, the middle (Cr, Fe)7C3 phase layer and the bottom FeCr solid solution phase layer. The structure and thickness of Cr23C6 phase layer formed in the early stage of chromizing play a decisive role in the inward diffusion of surface adsorbed Cr atoms and the growth rate of the permeated layer. With the C content of the matrix increases from low(0.08wt%C) to high(0.45wt.%C), the dense layer phases in chromized samples gradually changes from FeCr alloy phase with BCC structure to (Cr, Fe)23C6 and (Cr, Fe)7C3 carbides. And the wear resistance of the chromized layer increase. However, when the matrix C content is above 0.4 wt%, the structure and phases of the chromized layer are almost not affected by the matrix C content, so are the thickness and wear resistance. The results are helpful to the selection of steel matrix composition for chromizing and the optimization of chromizing process.

Influence of hydrogen on Kurdjumov-Sachs interfacial structure of M23C6/ferritic matrix at high temperatures

Secondary phase thermal stability and strengthening are strongly influenced by the interface structure between the secondary phase and the matrix. The influence of hydrogen on the interfacial structure of (Fe,Cr)23C6 carbides in ferritic matrix at high temperatures is systematically studied. The incoherent interface between (Fe,Cr)23C6 and ferrite matrix acts as a hydrogen trap region at high temperatures. Moreover, the hydrogen at high temperatures does not change the morphological features of (Fe,Cr)23C6 in the ferritic matrix. (Fe,Cr)23C6 obeys the Kurdjumov-Sachs orientation relationship with the ferritic matrix. Hydrogen at high temperatures decreases the mismatch between (Fe,Cr)23C6 and ferrite matrix interface from 7.65 % to 4.63 %. Furthermore, the (Fe,Cr)23C6 interface induced by hydrogen at high temperatures acts as a dislocation emission source. The decrease in interfacial misfit caused by hydrogen at high temperatures is the reason for (Fe,Cr)23C6 to maintain thermal stability and act as a dislocation emission source under a high-temperature hydrogen atmosphere.

Influence of carbon content on static recrystallization behavior of 50% cold-rolled Fe-18Mn-9Cr-2Al-xC steels

Recrystallization behavior during annealing at various temperatures was investigated for 50% cold-rolled Fe-18Mn-9Cr-2Al-xC steels with C contents varying between 0 and 0.5 wt%. Nucleation of recrystallization occurred near randomly in the carbon-free steel, whereas increasing the carbon contents promoted preferential nucleation at carbides formed along the grain boundaries through the particle stimulated nucleation mechanism. New grains in the carbon-free steel grow freely at the expense of deformed grains until the end of recrystallization during which migration of recrystallization front was blocked by the elongated δ-ferrites. For the carbon-added steels, on the other hand, (Cr,Mn)23C6 carbides and FeAl intermetallics formed during annealing and pre-existing carbides at grain boundaries pinned the recrystallization front, and thereby suppressing the growth of new grains and developing a distinct necklace structure. Recrystallization of the carbon-added steels completed only after carbides were dissolved at higher temperatures around 900 °C. It is noteworthy that it is not the carbon atom itself in solid solution but carbides that promotes nucleation of recrystallization and subsequently suppressed growth of new grains. It was also found that tensile properties of the cold-rolled steels restored nearly to those prior to cold rolling, i.e., in as-annealed state. It is concluded that recrystallization kinetics, special distribution of new grains, and texture of the cold-rolled Fe-18Mn-9Cr-2Al-xC steels are significantly affected by the carbon contents. In addition, restoration of tensile properties of cold-rolled steels by recrystallization suggests that many repetitive thermomechanical processing are applicable to the steels for forming into a desire shape.

Study on Wear Behavior of Coatings Fabricated by Additive Manufacturing Technology on the Surface of Guide Shoe of Shearer

This paper aims to obtain a fine wear-resistance cladding that can be applied in guide shoe of shearer. The performance of two cladding claddings fabricated by additive manufacturing technology, no chromium-high carbon (NCrHiC) claddings and high chrome-high carbon (HiCrHiC) claddings, was analyzed through a series of characterization experiments (optical microscope, hardness, coefficient of friction, wear rate, and surface morphology). The experimental results show that the NCrHiC cladding has obvious cracks and cracks are not observed on the surface of HiCrHiC cladding. However, the hardness and wear resistance of NCrHiC cladding is better than that of HiCrHiC cladding. The microstructure of NCrHiC cladding is composed of carbides, pearlite and ledeburite, and the one of HiCrHiC cladding is M(Fe, Cr)7C3 carbides and martensite. The worn width of HiCrHiC cladding is higher than that of NCrHiC cladding. Wear mechanism of NCrHiC cladding is abrasive wear while the one of HiCrHiC cladding is adhere wear.

Study on the composition, microstructure and properties of new W-Al alloyed ethylene cracking furnace tube under 1100 ℃ carburising test conditions

ABSTRACT The carburising tests were carried out at 1100 ℃ for 50 h, 100 h, 150 h and 200 h for a new type of tungsten-aluminium alloyed ethylene cracking furnace tube. The composition, microstructure transformation and performance of furnace tubes were analysed. The results showed that the average carbon content within 1 mm of the inner wall increased with the prolongation of carburising time. The thickness of carburised layer increased from 0.3 mm to 1.5 mm. The carbides in as cast structure were mainly massive (Cr, Fe, W)23C6 on the outside and fishbone (Cr, Fe, W)7C3 on the inside. During carburising process, the external (Cr, Fe, W)23C6 carbides coarsened and transformed into (Cr, Fe)7C3, and then gradually transformed into (Cr, Fe, W)7C3. Carbide coarsening mainly occurred in internal (Cr, Fe, W)7C3 during carburising. The carbide precipitation and transformation also led to Vickers hardness value of furnace tube increased.

Microstructure and mechanical property evolution mechanisms of 15Cr14Co12Mo5Ni2WA aviation gear steel during cold rotary forging

15Cr14Co12Mo5Ni2WA steel has huge application prospects in manufacturing aeroengine gears owing to its high strength and toughness. However, just because of its high strength, 15Cr14Co12Mo5Ni2WA steel is difficult to integrally deform at room temperature, which greatly restricts its industrial application. Cold rotary forging (CRF) is a local incremental metal forming process, and the small deformation force makes CRF ideal for deforming 15Cr14Co12Mo5Ni2WA steel. Thus, this paper is aimed to study the microstructure and mechanical property evolution mechanisms of 15Cr14Co12Mo5Ni2WA aviation gear steel during CRF process. The results show that grain size decreases from 26.2 μm to 16.9 μm, and the lattice orientation in each grain gradually becomes uniform during CRF process, which is mainly attributed to the combined effects of (Cr, Mo)23C6 carbide migration, dislocation movement and lattice rotation. Owing to the complex normal-external-transversal multi-directional metal flow, as-received ξ-fiber (<110>//ND) firstly transforms to single dominant Brass texture in CRF-20% condition, and then transforms to θ-fiber (<100>//ED) and Rotated-Cu texture at last deformation stage. Tensile/yield strength and Vickers hardness increase from 1049.3 MPa/1015.1 MPa and 316.6 HV in as-received condition to 1180.1 MPa/1146.7 MPa and 376.3 HV in CRF-50% condition, which is mainly attributed to the gradually increasing grain boundary strengthening, dislocation strengthening and secondary phase strengthening during CRF process.

PTA-Welded Coatings with Saturation Magnetization above 1.3 T Using FeCrBSi Powders with Chemical Composition Similar to AISI 430 Ferrite Stainless Steel

Fe-Cr-based soft magnetic alloy (SMA) monolayer coatings with high saturation magnetization (Ms) above 1.3 T were deposited onto AISI 1010 substrate by co-axial powder feeding plasma transferred arc (PTA) welding, using FeCrBSi self-fluxing powders Fe313, which have a similar chemical composition to AISI 430 ferritic stainless steel (FSS). The effect of welding parameters on the phase assemblage, microstructure, hardness and magnetic performance of the coatings was investigated. The results show that the coating’s maximum width and the welding surplus height increased with the rise in welding heat input and powder distribution density, respectively. The coating’s Ms increased sharply, but its coercivity (Hc) decreased with the growth in the substrate dilution ratio. The coating’s Hc increased whereas its Ms decreased with the increment in welding heat input. The as-welded coating C3 with optimum magnetic performance had a dendrites–eutectics composite structure, where the columnar or equiaxed sorbitic pearlite dendritic cores surrounded by network-like eutectics α(Fe,Cr) + (Fe1−xCrx)2B were the main contents. Moreover, (Fe,Cr)7C3 and CrB had also been detected, and they were mainly distributed in the interdendritic regions. The body-centered cubic (b.c.c.) α(Fe,Cr) multi-element solid solution contributes to a high Ms of 1.61 T, and the borides (Fe1−xCrx)2B and CrB as well as (Fe,Cr)7C3 and other carbides cause a high Hc of 58.6 Oe and hardness HV0.3 of 4.90 ± 0.06 GPa, much higher than that of AISI 430 FSS (HV &lt; 1.8 GPa). The current work verifies the feasibility of fabricating Ni- and Co-free FeCrBSi SMA coatings with high Ms and high hardness via PTA welding, and since the feedstock powders have chemical composition similar to AISI 430 FSS, the work may bring about novel applications for AISI 430 FSS in particular cases where the considerable wear-resistant performance as well as superior soft magnetic and anti-corrosive properties are required.

Fe-Mn-Al-C high-entropy steels with superior mechanical properties at 4.2 K

There exist urgent demands to develop structural materials with superior mechanical properties at 4.2 K. Some high-entropy steels (HESs) show potentials as cryogenic materials, but their deformation behaviors and mechanical properties at 4.2 K have been rarely investigated. Moreover, the aging-induced embrittlement of HESs also severely restricts their applications. In this work, the Fe-Mn-Al-C HESs with different Al contents (0, 4, 10 or 15 at.%) and grain sizes were fabricated, and their deformation behaviors and mechanical properties at 4.2 K were systematically studied. With increasing the Al content, (Fe,Mn)23C6 carbides are effectively inhibited in 10%Al HES after aging at 923 K for 10 days. Therefore, the premature fracture of 10%Al HES is avoided, leading to the excellent combination of high strength (∼1.5 GPa) and high fracture toughness (255 MPa·m1/2) at 4.2 K. The deformation mechanisms shift from the extensive twinning and deformation bands in 0Al HES to the lesser twinning, Taylor lattices and deformation bands in 10%Al HES, which contribute to the high strength and ductility of the 10%Al HES. Furthermore, the 10%Al HES with larger grains displays a much higher fracture toughness at 4.2 K, and this inverse size effect on the cryogenic toughness was elaborately revealed.

Effects of various double-quenching treatments on the microstructure and corrosion properties of D2 tool steel

The purpose of this paper is to study the effects of the various double-quenching treatments on the microstructure and corrosion properties of D2 tool steel. The percentage and the size of carbides and the phase types were parameters that affected the properties of various specimens. Both optical and field emission scanning electron microscopy were used to study the specimen microstructure. Moreover, the Tafel polarization, electrochemical impedance spectroscopy, and weight loss tests were evaluated to investigate the corrosion behavior. The obtained results showed that the martensite and tempered martensite phases exhibited the highest and lowest corrosion rates in 0.6 M NaCl solution, respectively. A Higher percentage of (Cr, Fe)7C3 carbides with a higher size also caused an increase in the corrosion resistance up to 91.2%. The lowest corrosion rate after 96 h was also related to tempered specimens.

Effect of WC particles preparation method on microstructure and properties of laser cladded Ni60-WC coatings

Ni60 and WC composite coatings were prepared on 17-4PH martensitic stainless steel with 30 wt% agglomeration-sintering WC (AS-WC) or 30 wt% sintering-crushing WC (SC-WC) respectively. The results show that in the AS-WC doped coating, the WC particles are more easily melted and dispersed, and a large amount of acicular (Fe, Ni, W)23C6 carbides are dispersed throughout the coating. However, in the SC-WC doped coating, the melting is quite limited and only occurs at the outer edge of the WC particles, and a small amount of (Fe, Ni, W)23C6 precipitated in the coating. Owing to this microstructure difference, the AS-WC doped coating possesses higher hardness, the microhardness reached 622.27 HV0.2 which is 25.5% higher than the normal Ni60 coating without WC, and 10.0% higher than the SC-WC doped coating. Moreover, the wear resistance test results indicate that the AS-WC doped coating has the best wear resistance compared to the SC-WC doped coating and normal Ni60 coating without WC. Those findings help us to obtain better Ni-based high hardness coatings for industrial applications.

Investigations on Microstructures and Properties of (Fe, Cr, W)7C3 Carbides by First Principles and Experiments

Tungsten doping is critical for the wear resistance and application of High-Chromium Cast Iron (HCCI). A series of investigations of (Fe, Cr, W)7C3 carbides were performed by first principles calculations and experimental analysis. The calculated results showed that with the increase in tungsten content in M7C3, the equilibrium cell volumes and the density gradually increased, and the formation energy of M7C3 carbides gradually decreased. The TEM results showed that the (Fe, Cr, W)7C3 carbides were (Fe3.27Cr2.99W0.74) C3 with a hexagonal structure after adding 2.13 wt % tungsten into laser cladding coatings of High-Chromium Cast Iron with a composition of Fe-26.8 wt % Cr-3.62 wt % C. These results from calculations and in situ nanoindentation show that tungsten doping could improve the ductility and indentation modulus of (Fe, Cr)7C3 carbides, and the composition of (Fe, Cr, W)7C3 was expected to be a high hardness and softness material. The wear test results showed that the wear resistance of tungsten-bearing HCCI was better than ordinary HCCI.

M7C3: The story of a misunderstood carbide

Since the discovery of the M7C3-type carbide in 1935, it has been the subject of many studies owing to it extensive usage in wear sensitive applications. Despite the technological importance of (Cr,Fe)7C3 carbides, attempts at using computational methods for tailoring its growth characteristics, stability and mechanical properties are hindered by the ambiguity associated with its atomisitic structure. The presented work aims at removing the former ambiguity regarding the atomistic structure of M7C3-type carbides. To this end we utilized EBSD (electron backscattered diffraction), TEM (transmission electron microscopy) diffractions and high-resolution STEM (scanning transmission electron microscopy) imaging, gathered from 9 zone-axis of the (Cr,Fe)7C3 phase formed in the as-cast AlCrFe2Ni2 high entropy alloy. Our experimental findings, supplemented by DFT calculations, indicates that only the hexagonal structure is a viable option. Additionally, we show that a carbon atom has to populate the center of a octahedral complex, a cite which was previously considered vacant. Furthermore, we demonstrate the co-existence of two variants of the newly revealed atomic structure which we believe were mistakenly identified as stacking faults in previous studies. The higher structural complexity of the newly identified structure, strengthened by the existence of spatially alternating variants, is suggested to partially justify the preference of this structure over the orthorhombic one. We believe that this study, and its like, are vital for aiding computational efforts aimed at controlling the growth, stability and performance of (Cr,Fe)7C3 carbides.

Corrosion resistance of niobium-added slag-free self-shielded flux-cored welding overlay in neutral solution

The niobium-added iron-based slag-free self-shielded flux-cored wire was developed and the effect of niobium addition on the corrosion resistance in neutral pH solution was investigated. The carbides, including NbC carbides, primary (Cr, Fe)7C3, and eutectic (Cr, Fe)3C carbides, remain intact after neutral corrosion, but the grain interface is corroded preferably for all the niobium-added welding overlays. The eutectic microstructure of 7.2 wt-% niobium-added welding overlay, which has more grain interface, leads to severe corrosion. When niobium addition reaches 14.4 wt-%, the welding overlay possesses the best corrosion resistance since more NbC carbides are formed, prophase austenite dendrite is precipitated, decreasing the grain interface, and chromium content is increased in the matrix of the hypoeutectic microstructure.

Microstructure and wear behavior of laser clad interstitial CoCrFeNi high entropy alloy coating reinforced by carbon nanotubes

In this study, the effect and characteristics of the laser clad interstitial CoCrFeNi high entropy alloy coating reinforced with carbon nanotubes (CNTs) was investigated. 1.0 wt% of CNTs were added as the reinforcement. To prepare composite powders before cladding, the CNTs and pre-alloyed CoCrFeNi powders were mechanically mixed without ball milling treatment. As a result, the microstructure of the CNTs on powder surface was well protected from serious damage. The effects of the CNTs upon the microstructure and wear behavior of the produced interstitial CoCrFeNi-CNTs coating were evaluated. The results showed that the intergranular (Fe, Cr)7C3/α eutectics were found to fully precipitate in the clad CoCrFeNi-CNTs coating. The hardness of the CoCrFeNi-CNTs coating was enhanced by 42.2% compared with that of the CoCrFeNi coating. The wear property was positively correlated with the hardness. The wear rate of the CoCrFeNi-CNTs coating (2.18 × 10−5 mm3·N−1·m−1) was significantly lower than that of the CoCrFeNi coating (10.54 × 10−5 mm3·N−1·m−1). The enhancements of the wear property originated from the solution strengthening of carbon on grains and the precipitation strengthening of (Fe, Cr)7C3 carbides on grain boundaries. In wear process, the lamellar (Fe, Cr)7C3/α eutectics deposited on worn surface and eventually formed a carbide hardening layer structure and prevent severe wear on the CoCrFeNi-CNTs coating.

Influences of carbon concentration on microstructure and tensile properties of Fe–18Mn–9Cr–2Al–xC steels

As an effort to develop corrosion resistant and highly formable austenitic steels, Fe–18Mn–9Cr–2Al–(0–0.5)C steels in wt. % were designed and their microstructures and tensile properties were investigated with particular attention being paid to the effects of carbon concentration. The carbon-free steel consisted of the austenite, δ-ferrite and ε-martensite phases in as heat-treated condition while those of carbon-added steels had an austenite single phase with the (Fe,Cr)23C6 carbides at grain boundaries. When tensile strained at room temperature, all the steels exhibited extensive deformation twinning, resulting in large work-hardening and excellent ductility. Deformation twinning was suppressed at 300 °C, and dynamic recrystallization took place partially at grain boundaries when strained at 600 °C. The addition of Cr and hence formation of carbides in carbon-added steels have little influence on plasticity of the conventional twinning-induced plasticity steels, suggesting the possibility of developing Cr-bearing TWIP steels with both corrosion resistance and excellent formability.

Influences of Si content on the high-temperature oxidation behavior of X10CrAlSi18 ferritic heat-resistant stainless steel at 700 °C and 800 °C

X10CrAlSi18 FHSS (ferritic heat-resistant stainless steel) has received a lot of attention due to its advantageous combination of creep resistance and oxidation resistance. The influence of Si content on the high-temperature oxidation resistance of X10CrAlSi18 FHSS after oxidation at 700 and 800 °C for up to 180 h in air was investigated in this study. According to the results, a higher Si content could coarsen the grain of ferrite and simultaneously increased the amount of (Cr, Fe)23C6 carbides, which caused cracks and reduced the adhesion between the oxide film and the matrix. After oxidation at 700 °C, the oxide film of 0.77Si FHSS and 1.35Si FHSS were found to be primarily composed of Al2O3, SiO2, Cr2O3, Fe2O3, Mn2O3 and MnCr2O4, with thickness of 5.10 μm and 5.56 μm, respectively. The oxide films formed at 800 °C were primarily composed of Al2O3, SiO2, Cr2O3, FeCr2O4, Mn2O3 and MnCr2O4 with thickness of 5.55 μm and 7.37 μm, respectively. A higher Si content was discovered to increase the amount of MnCr2O4 in the outer layer of the oxide film, which resulted in a looser spinel structure and reduced the oxidation resistance of X10CrAlSi18 FHSS.

Evolution mechanism and precipitation kinetics of carbides in 50Cr6Ni2Y alloy steel by direct laser deposition

Carbides as main reinforcing phase play a significant role in direct laser deposition (DLD) 50Cr6Ni2Y alloy steel with high hardness and wear-resistant. The 50Cr6Ni2Y alloy steel samples were prepared with different laser energy average densities (EAD) from 90 J/mm2 to 110 J/mm2. Subsequently, the precipitation and evolution mechanism of carbides were studied by X-ray diffraction (XRD), scanning electron microscope (SEM), Transmission electron microscope (TEM), etc. The results indicate that the DLD samples were mainly composed of fine bainite ferrite (BF) and nano-sized (Fe,Cr)23C6 and (Fe,Cr)7C3 carbides. Herein, the dispersed nano-sized carbides attributed to the precipitation strengthening, which could improve the mechanical property of the samples. The carbides nucleated and grew at the intersection of the BF steps, and part of the carbide particles were surrounded by the fast-growing BF during the growth process. With the increase of EAD, more C dissolve into BF instead of forming carbides, which causes the carbide fraction to drop from 11.5 ± 1.8% to 2.1 ± 0.5%. The parameter k of carbide precipitation kinetic equation was calculated as 16.36443 ± 0.51, and the modified kinetic equation was obtained, which can be used to control the volume fraction of carbides in DLD 50Cr6Ni2Y alloy steel. The sample with 100 J/mm2 EAD had the best matching performance of strength (hardness of 537 HV and tensile strength of 1294 MPa) and toughness (elongation of 5.5%) because of 5.8 ± 1.3% fraction carbide precipitation. This research may provide a basis and technical reference for future studies on the precipitation and evolution mechanism of carbides in DLD 50Cr6Ni2Y alloy steel.

Promoting in situ formation of core‐shell structured carbides in high‐Cr cast irons by boron addition

AbstractM7C3 carbide is an important reinforcing phase in high‐Cr cast irons, ferrous alloys, metal‐matrix composites, and hardfacing overlays. However, the mismatch at the carbide/matrix interface due to the differences in structure and mechanical strength between the carbide and metallic matrix may lower the resistance of the material to mechanical attack, such as wear, corresponding to increased risk of interfacial failure or the role of the interfacial mismatch as a stress raiser for crack initiation. Recent studies on high‐Cr cast irons (HCCI; Fe‐45%Cr‐%C series) show that core(M7C3)‐shell(M23C6) structured carbides (CSSCs) help minimize the misfit stress at the interface between carbide and matrix, thus enhancing their resistance to wear. However, such core‐shell structured carbide does not always form. It is of importance to understand the mechanism responsible for the formation of CSSC for maximized benefits. In this study, we conducted thermodynamic analysis to investigate the conditions for in situ forming CSSCs in HCCIs and determine the probability of generating CSSCs through alloying elements. Both thermodynamic analysis and first‐principles calculations demonstrate that the core‐shell structured carbide can be in situ formed in HCCIs by alloying with elements such as boron, which increases the stability of M23C6 with lowered energy. Relevant experiments were performed to verify the theoretical analysis and prediction.