Iron Chromium Research Articles

Study on Diffusion Kinetics and Law of Chromium on the Surface of Low-Carbon Steel

Cr/low-carbon steel surface composites were prepared by aqueous solution co-deposition and high-temperature solid-state diffusion technology, and the macro rule of the solid-state diffusion of chromium on the surface of low-carbon steel was analyzed. The molecular dynamics (MD) method was used to simulate and calculate the diffusion process of the Cr/Fe interface, and the macro and micro diffusion mechanisms were analyzed. The results show that the diffusion of the chromium in iron is the combined action of the temperature, crystal structure and lattice distortion, and the diffusion coefficients of chromium in α-Fe and γ-Fe have little difference. The vacancy diffusion mechanism of the first adjacent transition is the main diffusion mode. In practice, chromium atoms diffuse along the grain boundaries of the low-carbon steel matrix and provide pinning at the grain boundaries to prevent grain growth. The simulation law is in good agreement with the experimental law. The variation law of the average diffusion coefficient of chromium atoms with temperature is obtained. The diffusion rate of chromium in the bcc crystal structure is obviously higher than that in the fcc crystal structure. In the same crystal structure, the diffusion coefficient of chromium increases with the increase in temperature. However, in the lattice transition temperature region, the diffusion coefficient of chromium gradually decreases with the increase in temperature until the end of the transformation.

Optimize the corrosion behavior of AISI 204Cu stainless steel in different environments under previous cold working and welding

Enhancing corrosion resistance in stainless-ssteel alloys is a paramount objective in the petroleum industry. This study investigated the effects of the previous cold working and welding processes on the mechanical properties and corrosion rates of 204 Cu stainless steel in different aggressive environments (crude oil, freshwater, and seawater). The experimental sets were supported by microstructure analysis. The mean weight loss method was employed to determine the corrosion rates, which were optimized using the Taguchi method. The ferrite and austenite phase bands, as well as the deformed portions of austenite, are pushed to flatten out during cold working, which increases the material’s hardness. Cold-worked steels were welded, creating an annealed area around the HAZ in addition to the usual weld zones, which demonstrated partial microstructure recovery and hardness reduction. HAZ showed signs of iron overload and chromium nitride precipitation. Cold-worked specimens only showed reduced corrosion resistance to 30% of the initial rate and reduced thickness. Moreover, the Taguchi optimization technique indicated that the corrosion environment has the most effect on the corrosion rate compared to the cold work ratio for welded and non-welded stainless-steel specimens.

Structure of the surface layer of high-chrome steel nitridated in the elion regime in the plasma of a suspended arc discharge with a heated cathode

The purpose of this work is to reveal the patterns of formation of the structure of the surface layer of high-chromium steel subjected to nitriding in a low-pressure gas discharge plasma using a plasma generator with a hot cathode "PINK". Heating of the samples to the nitriding temperature was carried out by the ionic component of the plasma, as well as by the electron and ionic components of the plasma (elion mode). The object of the study was heat-resistant corrosion-resistant steel of the austenitic class grade 20X23H18 (foreign analogue of AISI310S). The relevance of research is due to the relatively low level of hardness and wear resistance of steels of this class. Nitriding of steel was carried out on the TRIO installation, retrofitted with a switching unit for implementing the aelion (electronic and ionic) processing mode. It has been established that the thickness of the hardened layer is (55-60) pm and weakly depends on the method of nitriding, temperature (in the range of 793-873 K), and duration (3-5 hours) of the process. A nitriding regime has been revealed that makes it possible to form a surface layer with a microhardness of 13.7 GPa (ionic heating mode) and 10.8 GPa (elion heating mode). It has been established that the high strength and tribological properties of nitrided steel are due to the formation of a nanocrystalline structure in the surface layer, the main phases of which are iron nitrides Fe4N and chromium nitrides CrN. It is shown that heating the samples to the nitriding temperature in the aelion mode, which uses the electron and ion components of the plasma, leads to a significantly lower level of material roughness compared to the samples heated during nitriding by the ion component of the plasma.

Effects of Salt Bath Nitriding Process on AISI 309 Stainless Steel

AISI309 stainless steel is a type of austenitic stainless steel that contains a high percentage of chromium and nickel, along with a small amount of manganese. It is designed to be used in high-temperature applications, such as in furnace parts and heat exchangers. Low temperature salt bath nitriding process was carried out on AISI 309 stainless steel at 550°C for time duration of 80, 160 and 240 minutes. The characteristics of the nitride surface were thoroughly assessed. The microstructure and phase components of the nitrided surface revealed a hardened layer of chromium nitride and iron nitride on the specimen surface. The case depth and the surface hardness were strongly influenced by the alloying components. To analyze the wear, a pin on disc machine was utilized and the wear test was carried out. From the wear test, wear loss were determined. Scanning electron microscopy revealed the variation between loss of material and the base material. A specimen which is untreated is kept aside and comparisons of results were done with nitrided samples.

The Reductive Leaching of Chalcopyrite by Chromium(II) Chloride for the Rapid and Complete Extraction of Copper.

A hydrometallurgical process is developed to lower the costs of copper production and thereby sustain the use of copper throughout the global transition to renewable energy technologies. The unique feature of the hydrometallurgical process is the reductive treatment of chalcopyrite, which is in contrast to the oxidative treatment more commonly pursued in the literature. Chalcopyrite reduction by chromium(II) ion is described for the first time and superior kinetics are shown. At high concentrate loadings of 39, 78, and 117 g L-1 , chalcopyrite reacted completely within minutes at room temperature and pressure. The XRD, SEM-EDS, and XPS measurements indicate that chalcopyrite reacts to form copper(I) chloride (CuCl). After the reductive treatment, the mineral products are leached by iron(III) sulfate to demonstrate the complete extraction of copper. The chromium(II) ion may be regenerated by an electrolysis unit inspired by an iron chromium flow battery in a practical industrial process.

Electrolyte engineering for effective seawater splitting based on manganese iron chromium layered triple hydroxides as novel bifunctional electrocatalysts

The use of anionic inhibitor, especially carbonate, provide a much-needed anionic protective layer at anode surface, selectively restricting chlorides but allowing hydroxides thereby favouring OER over CER during direct seawater electrolysis.

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>

Осаждение силицида титана на нержавеющую сталь AISI304

Introduction. Metal-ceramic coatings based on titanium silicide are promising for protecting stainless steel AISI 304 from wear, corrosion and high-temperature oxidation. Purpose of the work: to investigate the stainless steel AISI 304 surface layer structure after electrospark deposition in a mixture of titanium granules with silicon powder, and to study oxidation resistance, corrosion resistance and tribotechnical properties of the obtained coatings. Research methodology. Fe-Ti-Si coatings on the stainless steel AISI 304 samples were obtained by electrospark machining with a non-localized electrode consisting of titanium granules and 2.6-6 vol.% mixture of titanium and crystalline silicon powders. Results and discussion: it is shown that a stable positive gain of the cathode is observed when the proportion of silicon in the powder mixture does not exceed 32 vol.%. The phase composition of the coatings includes: a solid solution of chromium in iron, titanium silicide Ti5Si3, titanium and silicon, which is confirmed by the energy dispersion analysis data. The microhardness of Fe-Ti-Si coatings ranges from 10.05 to 12.86 GPa, which is 5-6 times higher than that of uncoated steel AISI 304. The coefficient of friction of the coatings is about 20% lower compared to steel AISI 304 and hovers around 0.71-0.73. Wear tests in dry sliding mode show that Fe-Ti-Si coatings can increase the wear resistance of steel AISI 304 up to 6 times. The oxidation resistance of the coatings at a temperature of 900 ̊С is 7-12 times higher as compared to steel AISI 304. The conducted studies have shown that new electrospark Fe-Ti-Si coatings can increase corrosion resistance, oxidation resistance, microhardness, as well as reduce the coefficient of friction and wear rate of the stainless steel AISI 304 surface.

Highly Ion Selective Proton Exchange Membrane Based on Sulfonated Polybenzimidazoles for Iron–Chromium Redox Flow Battery

The iron–chromium redox flow battery (ICRFB) has great potential for large-scale energy storage, due to its low capital cost of redox-active materials. However, the trade-off between conductivity and selectivity in the membranes limits its applications. Herein, a series of sulfonated polybenzimidazoles with exactly controlled sulfonation degree (SD) (S-PBI-x, x refers to SD) are designed and synthesized via direct copolymerization from the sulfonated monomer. Combined with the electrostatic repulsion of the formed imidazoliums, the S-PBIx membranes facilitate the proton transport and repel the redox-active ion crossover efficiently. Especially, when compared with Nafion 212 membrane, the S-PBI-100 membrane displays a comparable conductivity and more than an order of magnitude lower Fe3+ and Cr3+ permeabilities. Thus, a higher columbic efficiency (CE) of 98.2% and energy efficiency (EE) of 83.17% are achieved at 80 mA cm–2 for the corresponding ICRFB. Most importantly, no chemical degradation is observed for the S-PBI-100 membrane after in situ and ex situ stability tests.

The Recycling of Waste Per-Fluorinated Sulfonic Acid for Reformulation and Membrane Application in Iron-Chromium Redox Flow Batteries

Iron–chromium redox flow batteries (ICRFB) possess the advantage of low raw material cost, intrinsic safety, long charge–discharge cycle life, good life-cycle economy, and environmental friendliness, which has attracted attention from academia and industry over time. The proton exchange membrane (PEM) is an important part of the ICRFB system, impacting the efficiency and lifetime of the battery. Currently, the most widely used PEMs in the market are per-fluorinated sulfonic acid (PFSA) membranes, which possess high electrolyte stability and achieve the separation of positive and negative electrolytes. In addition, the complex preparation process and extremely high market price limited the usage of PEM in ICRFB. In this paper, we developed a remanufactured membrane (RM) strategy from waste PFSA resins. The RM has higher electrical conductivity and better proton transport ability than the commodity membrane N212. In the cell performance test, the RM exhibits similar coulombic efficiency (CE) as N212 at different current densities, which is stabilized at over 95%. Furthermore, the voltage efficiency (VE) and energy efficiency (EE) of the RM are improved compared to N212. At a current strength of 140 mA cm−2, the degree of energy loss is lower in the RM, and after 60 cycles, the capacity decay rate is lower by only 16.66%, leading to long-term battery life. It is a cost-effective method for membrane recovery and reformulation, which is suitable for large-scale application of ICRFB in the future.

Experiments and modeling of the macroscale mechanical responses of neutron-irradiated FeCrAl alloys

Iron chromium aluminum (FeCrAl) alloys have been regarded as candidate materials for accident-tolerant fuel cladding. In this study, the stress-strain curves of various neutron-irradiated and un-irradiated FeCrAl alloys at the test temperatures of 300 K and 653 K are obtained through the uniaxial tensile tests, with the fast neutron fluences of 2 × 1019 n/cm2 and 8 × 1019 n/cm2 (E ≥ 1 MeV). Simultaneously, improved shear strain rate model and damage evolution model are proposed in the crystal plasticity theoretical frame, with the irradiation effects involved. The developed models are numerically implemented, with the simulation results of the macroscale stress-strain curves agreeing well with the experimental data. The irradiation hardening and embrittlement phenomena are captured, together with the characteristics of strain hardening and softening. The influences of alloy compositions, temperatures, and fast neutron fluences on yield strength, ultimate tensile strength, yield ratio, and uniform elongation are discussed. Macro mechanical properties such as yield strength and yield ratio are found to be near-linearly correlated with crystal plasticity model parameters. A model for multi-objective optimization of the mechanical properties is established, with which the optimum design strategies of alloy composition for the materials in the in-reactor service environments are proposed. This study could provide a theoretical basis for the research and development of advanced FeCrAl alloys.

Synthesis of (Fe,Cr)2O3 solid solution pigment powders for ink application

AbstractIron chromite pigment was synthesized via solution combustion using iron(III) nitrate nonahydrate and chromium(III) nitrate nonahydrate as starting materials, and glycine, urea, citric acid, and ethylene glycol as fuels. The effect of postheating temperature on the structure, microstructure, and chromatic properties of the synthesized powders was also studied. X‐ray diffraction patterns showed that the as‐synthesized powders were amorphous to crystalline FeCr2O4 phases, depending on fuel type. Moreover, regardless of the fuel type, postheating led to the d‐space shift and oxidation and formation of (Fe,Cr)2O3 solid solution. Phase transformation of FeCr2O4 to (Fe,Cr)2O3 solid solution was observed at 500/750°C depending on the dominant phase present in the as‐synthesized particles. Fourier transform infrared analysis illustrated a shift in the band position of octahedral M–O and tetrahedral M–O bonds due to the movement of Fe cations and the lattice shrinkage by increasing the postheating temperature. Moreover, scanning electron micrographs showed that Fe0.7Cr1.3O3 semispherical fine particles consisted mainly of porous and spongy FeCr2O4 particles due to the oxidation and phase transformation during postheating. According to chromatic measurements, the ink prepared by using the powders synthesized in the presence of glycine and post‐heated at 500°C showed reddish‐brown color which could be considered a promising candidate for tile decoration application. Furthermore, rheology studies revealed that the prepared ink showed non‐Newtonian shear thinning behavior.

Raman identification and characterization of chemical components included in simulated nuclear fuel debris synthesized from uranium, stainless steel, and zirconium

ABSTRACT Raman spectroscopy is a powerful technique for studying nuclear materials. However, it has been scarcely utilized for nuclear fuel debris. Here, we present a Raman study of several types of simulated nuclear debris synthesized from uranium, stainless steel, and zirconium to identify and characterize chemical components included in the simulated debris. Raman spectroscopy sensitively identified many kinds of chemical components: cubic UO2, U3O8, (Fe,Cr)UO4 (iron–chromium uranate), spinel oxides, monoclinic ZrO2, tetragonal ZrO2, and Zr3O. Some details concerning the chemical states of each component included in the simulated debris were obtained (e.g. spinel oxides were suggested to consist of Fe, Cr, Ni, Zr, and U). The results obtained here will be helpful in the Raman analysis of actual nuclear debris, such that in the Fukushima Daiichi nuclear power plants.

Influence of boron- and barium-containing modifiers on the structure of low-chromium cast iron

The paper presents the results of studying the effect of modifying low-chromium hypoeutectic cast iron (chromium content about 1%) with boron- and barium-containing additives on its structure and hardness. The modification was carried out with carbothermicferroboron (0.08% of weight of the liquid metal); ferrosilicobarium (0.05% of weight of liquid metal); complex boron barium ferroalloy (0.14% by weight of liquid metal). The microstructure and properties were compared with a sample of unmodified cast iron of the same composition.The Thixomet Pro software was used as the main method of the quantitative analysis of the microstructure that allows quantitative metallographic analyzing with high accuracy and repeatability.The analysis of the results obtained shows a positive effect of modification on changes in the microstructure. In all the experimental samples, grinding and more uniform distribution of carbides, as well as transformation of the carbides morphology from dendritic to compact granular form, take place. Pearlite colonies in the modified cast iron are characterized by a higher degree of dispersion than in the reference sample. Such changes in the structure lead to increasing the hardness of the prototypes.

Impact of dredging on the environmental state of a small river with considering the composition of bottom sediments

Reports on the environmental impact assessment of planned activities aimed at restoring the hydrological regime and sanitation of rivers do not always pay attention to in-depth analysis of the physicochemical composition of bottom sediments. The silt deposits have proven to be a good ameliorant for agricultural lands, provided they are of satisfactory quality. Bottom sediments, especially their fine alluvial fraction, accumulate various compounds and trace elements, including heavy metals. Analysis of the content of iron Fe, manganese Mn, cobalt Co, chromium Cr and determination of the integrated level of contamination of bottom sediments did not reveal their toxic contamination in the area of the village Kleshnivka and the village Petrykivka. Determination of "geoaccumulation indices" by G.M. Mueller allowed to classify the sediments of the Chaplinka River as unpolluted, and the man-caused load on the hydroecosystem as low. In compliance with the recommendations on the content of Mn grades in the soil cover of the obtained fifth Igeoclass, which provides heavy pollution and significant man-caused load on the hydroecosystem. To characterize the processes occurring in the hydroecosystem of the Chaplynka River, the bottom accumulation coefficient was calculated. The assessment of the ecological status of hydroecosystems revealed an overwhelming ecological emergency. There is a significant threat of deposits of iron Fe, manganese Mn in bottom sediments. Despite the low risk of contamination of bottom sediments with chromium Cr, the risk will increase due to the rather variable chemical composition of surface waters, and hence the possibility of an ecological crisis for the hydroecosystem. The sanitary condition of a small river could be improved by restoring its hydrological regime. The decrease in the efficiency of dredging works is related to the regulation of the regulation of the riverbed. In the vast majority of cases, hydraulic structures are not provided for or do not correspond to the current level regime of watercourses. After clearing the river bed, there is a danger of their secondary silting, due to the abandonment of part of the temporary dumps on the banks within the water protection zones without fixing.

A study of the solidification and stability mechanisms of heavy metals in electrolytic manganese slag-based glass-ceramics.

To better solve the waste pollution problem generated by the electrolytic manganese industry, electrolytic manganese slag as the main raw material, chromium iron slag, and pure chemical reagents containing heavy metal elements mixed with electrolytic manganese slag doping. A parent glass was formed by melting the slag mixture at 1,250°C, which was, thereafter, heat-treated at 900°C to obtain the glass-ceramic. The results from characterizations showed that the heavy metal elements in the glass-ceramic system were well solidified and isolated, with a leakage concentration at a relatively low level. After crystallization, the curing rates of harmful heavy metals all exceed 99.9%. The mechanisms of heavy metal migration, transformation, and solidification/isolation in glass-ceramic curing bodies were investigated by using characterization methods such as chemical elemental morphological analysis, transmission electron microscopy, and electron microprobe. The most toxic Cr and Mn elements were found to be mainly kept in their residual state in the glass-ceramic system. It was concluded that the curing mechanism of the heavy metals in a glass-ceramic can either be explained by the chemical curing induced by bonding (or interaction) during phase formation, or by physical encapsulation. Characterization by using both Transmission electron microscopy and EPMA confirmed that Cr and Mn were mainly present in the newly formed spinel phase, while the diopside phase contained a small amount of Mn. Zn, Cd, and Pb are not found to be concentrated and uniformly dispersed in the system, which is speculated to be physical coating and curing.

Combustion Characteristics and Performance Evaluation of Modified Mesoscale Annular Combustor

ABSTRACT The combustion characteristics and performance of a cylindrical stagnation flow-type mesoscale annular combustor were evaluated. The combustor comprised inner and outer porous tubes made of stainless steel and nickel – chromium–iron alloy, respectively. A rich C3H8–air mixture and air were supplied to the inner and outer tubes, respectively. The cylindrical flame was formed around the inner tube; consequently, a petal-type flame was formed downstream of the cylindrical flame. Experiments were conducted by maintaining a constant flow rate q i of the rich C3H8–air mixture in the inner tube while varying the equivalence ratio φ i of the mixture and the airflow rate q o of the outer tube. To investigate the combustion characteristics, the temperature was measured inside and at the outlet of the combustion chamber. The burned gas compositions, O2, CO, and NO, were analyzed. The heat loss rate η hl and the exergy loss rate η ex,loss were evaluated from the obtained temperature data. The minimum values of η hl and η ex,loss were 0.06 at φ i = 1.5, φ all = 0.3, and 0.44 at φ i = 5.0, φ all = 0.8, respectively. The values of η hl and η ex,loss verified that the combustor offers high performance.

Phase transformation of FeCr2O4 to (Fe,Cr)2O3 solid solution pigment powders: Effect of post‐heating temperature

AbstractIron chromite powders were synthesized via solution combustion route using iron(III) nitrate nonahydrate and chromium(III) nitrate nonahydrate as starting materials, as well as glycine–urea, glycine–citric acid, and glycine–ethylene glycol mixtures as fuels. The effect of postheating at different temperatures on the structure, molecular, microstructure, and chromatic properties of powders and tiles colored by in‐glaze powders was studied. The X‐ray diffraction patterns showed that as‐synthesized powders were obtained in crystalline FeCr2O4 phases moreover, postheating of the powders led to d‐space shift and oxidation and formation of (Fe,Cr)2O3 solid solution phase regardless of fuel type. Phase transformation of FeCr2O4 to (Fe,Cr)2O3 solid solution was observed at 500/750°C depending on the dominant phase of as‐synthesized particles. Fourier transform infrared analysis illustrated that the band positions of octahedral M–O and tetrahedral M–O bonds were shifted due to Fe cations movement from their position and lattice shrinkage by increasing of post‐heating temperature. Moreover, scanning electron micrographs showed that Fe0.7Cr1.3O3 semispherical fine particles were formed from porous spongy FeCr2O4 particles due to oxidation and phase transformation during the postheating. Furthermore, chromatic properties of the samples were represented. The color properties of the pigments showed that the formation of brown pigments is provided with the phase transformation from FeCr2O4 to (Fe,Cr)2O3 at a temperature of up to 750°C. Moreover, increasing the color purity to this temperature is related to the removal of residual carbonaceous matters. The chromatic properties of the glazed tiles colored using the pigments showed that postheating between 250 and 500°C led to more brown appearance.

The Effect of Mineral Pigments on Mechanical Properties of Concrete

Pigmented concrete exhibits artesian properties in addition to ordinary concrete properties, explicitly high strength, excellent durability, and weather resistance. However, the influence of several parameters that affect the characteristics of colored concrete should be studied; extensively. In this paper, the impact of the w/b (water/binder) ratio using color pigments on the mechanical properties such as compressive and flexural strengths of colored cement mortar prisms and cubes experimentally investigated. The experimental program included 21 mixes with six cubes and three flexural prisms specimens for assessing compressive and flexural strength, respectively. The blends included different water/binder ratios with values of 0.4, 0.5, and 0.6, in addition to several color pigments as a partial replacement of cement. The percentage of replacements altered between 0, 2.5%, 5% and 7.5% with two different shades of pigments consisting of red iron and green chromium oxide. Based on the experimental results, empirical expressions were generated based on Abram’s law to assess the relationship between the compressive strength of colored concrete and w/b ratio. The results revealed that the compressive and flexural strength of colored concrete is influenced by w/b ratio and partially replacement percentage of cement by color pigment not proportionally direct. Furthermore, the shade of pigments also has a different impact as well.

Effect of (NbTi)C Particles on the Microstructure and Hardness of High Chromium and Nickel Indefinite Chilled Cast Iron

High chromium and nickel indefinite chilled cast iron (ICCI), as an excellent hot roll material, is the preferred roll variety due to its good combination of surface roughness, hot crack resistance, and hot wear resistance. The microstructure and hardness of ICCI roll materials with different contents of (NbTi)C particles is studied here, and the microstructure evolution process is analyzed by X-ray diffraction. The influence of (NbTi)C particles on the carbide morphology and distribution is investigated by metallographic microscopy and scanning electron microscopy, and the existence of (NbTi)C particles is observed. The experimental results show that (NbTi)C particles are present in granular, rod, and polygonal forms. Combined with a Thermo-Calc solidification phase diagram, it is found that the (NbTi)C particles undergo eutectic precipitation in the melt, forming short rod-shaped (NbTi)C carbides with a size of about 10 μm. Through the Rockwell hardness test, it is found that the hardness after adding 0.8 wt % (NbTi)C particles was 54.4 HRC, which was 21.1% higher than that without the addition.