Brittle Compounds Research Articles

Microstructural evolution and analysis of Zr–Co/Cu–Al glassy composites and crystallized alloys via indentation and MD simulations

B2-containing bulk metallic glass (BMG) composites are still attractive due to their unique deformation mechanism and positive effect on work-hardening and ductility. As stated in review [1], the competition between B2 phase formation, retention of amorphous matrix and intermetallic compounds depends on several parameters, such as alloy composition and cooling rate. For a given BMG composite containing B2 phase, the glass matrix, B2 phase, and brittle compounds generally coexist. As a result, the relationship between microstructures such as atomic diffusion and micro-indentations must be investigated. In this work, nano-indentation, micro-hardness, and molecular dynamics (MD) simulations were performed on two Zr–Co/Cu–Al BMG composites with certain differences in amorphous matrix and crystalline phases such as their distribution, volume fraction, or types. The results indicated that the (1) formation of B2 phase, and precipitation of brittle compounds substantially differed; (2) the atomic transfer in these indented positions can be observed in simulated experiments and line scanning images (energy dispersive spectroscopy) for alloy compositions; (3) the degree of atomic diffusion in BMG composites functioned as the depth of nano-indentation via MD simulations; (4) the differences in nano-deformation via MD simulations can be observed for Zr–Cu alloys with various crystals; (5) the micro-indentation may stimulate transformation or B2 phase formation in localized regions upon indented stress; (6) the simulated results and experimental outcomes were mutually corroborated. These results also give a hint that atomic diffusion and phase formation in multiple mingled microstructures really existed, but they were very complicated and different in localized areas. This research is important and provides a clue for further exploration of the relationship between deformation and atomic diffusion.

Exploring avoiding brittle compounds in brazed joints of C/C composites and DD3 alloys through surface modification

Joining C/C composites to Ni-based single crystal alloy DD3 can significantly broaden their industrial application. The currently used active brazing method (ABM) may cause harmful reactions with Ni-based alloys, generating brittle compounds and deteriorating joint performance. In this work, a two-step method involving chromium carbide (Cr–C) surface modification and brazing using pure Cu filler is first developed to explore avoiding brittle compounds in joints. Surprisingly, the brazed seam of joints is mainly composed of (Cu, Ni) solid solution (s, s) without generating brittle compounds. At the DD3 interface, only (Ni, Cu) (s, s) and (Cu, Ni) (s, s) layers are formed. Besides, (W, Mo) (s, s) particles are precipitated nearby the DD3 substrate. For the C/C interface, the Cu filler is tightly joined to the Cr–C layer without forming new phases. The joint microstructure has no significant change with the variation of the Cr–C layer thickness. As increased the Cr–C layer thickness, the joint strength first increases and then decreases. The maximum shear strength of ∼32 MPa is obtained when the Cr–C layer thickness is ∼4.6 μm. The joint shear strength decreases with increased testing temperatures, which can still be maintained at ∼28 MPa at 600 °C. The surface modification and brazing strategy in this work can be further applied to the joining of other carbon materials and ceramics with poor wettability.

Systematic study on the optoelectronic and elastic properties of Cu-based ternary chalcogenides: Using ab-initio Approach

The first principles-based GGA approach is used to investigate the elastic and optoelectronic properties of Cu-based ternary chalcogenides QCu3Te4 (Q = Ta, V, Nb) to explore their potential and significance in photovoltaic applications. The calculated energy band structures using GGA approach were corrected using hybrid GGA + U functional. Our study demonstrates that QCu3Te4 (Q = Ta, V, Nb) are the semiconductors with indirect energy band gaps as CBM and VBM occur at different symmetric points (R-X). The Bandgap values of QCu3Te4 (Q = Ta, V, Nb) are reduced by replacing Ta with V and Nb; thereby, the values of bandgaps are 1.5, 0.49, and 1.41 eV for TaCu3Te4, VCu3Te4 and NbCu3Te4, respectively. Therefore, a detailed examination of the optical parameters is performed to demonstrate the prospect of QCu3Te4 (Q = Ta, V, Nb) for optoelectronic device applications. The calculated results revealed that QCu3Te4 (Q = Ta, V, Nb) could be used as antireflecting coatings as such materials are weak reflectors of incident photons and reflect a maximum of 45% photo radiations in the upper UV region. Since VCu3Te4 is an efficient absorber of incident photo radiations in the infrared region, the TaCu3Te4 and NbCu3Te4 show maximum absorption in the visible and near UV regions. Furthermore, in the elastic properties the Poisson's ratio ‘σ’ indicates that QCu3Te4 (Q = Ta, V, Nb) are covalent compounds and are anisotropic as the values of Zener anisotropy factor ‘A’ is not equal to 1. Also, the Pugh's ratio (B/G) values for QCu3Te4 (Q = Ta, V, Nb) are under 1.75. Thus, these Cu-based chalcogenide materials are brittle compounds that can provide an efficient route for optoelectronic devices. It is evident from the spectra of S that NbCu3Te4/TaCu3Te4 are p-type semiconductors; however, VCu3Te4 is an n-type semiconductor. We can predict that TaCu3Te4 is the most promising thermoelectric material for TE devices.

Brazing of SiC ceramic to Al0.3CoCrFeNi high entropy alloy by graphene nanoplates reinforced AgCuTi composite fillers

Graphene nanoplates reinforced AgCuTi composite fillers are applied to braze SiC ceramic with Al0.3CoCrFeNi high entropy alloys. Graphene nanoplates, together with active element Ti which could restrain the activity of multiple elements from Al0.3CoCrFeNi, impede the intense diffusion towards SiC and thus avoid the formation of bulk brittle compounds unfavorable to the joint performance. The in situ synthesized reaction between Ti and graphene nanoplates leads to dispersive TiC reinforcements which not only promote the refinement of the joint microstructure but also relieve the residual stress that existed in SiC/Al0.3CoCrFeNi joint. Vigorous dissolution and diffusion across Al0.3CoCrFeNi/liquidus filler interface lead to laminated Ti-rich layers formed adjacent to Al0.3CoCrFeNi substrate. The uniform and continuous reaction layer of TiC/Ti2Ni-type compounds/Ag(Cu) inclusions is formed adjacent to SiC ceramic. Tiny TiC particles and Ti2Ni-type compounds distribute evenly in the brazing seam, strengthening the joint performance. Eventually, the maximum shear strength of 36.7 MPa is achieved when adding 0.3 wt% graphene nanoplates.

Influence of silicon carbides on the structure and properties of composite nickel-phosphorus coating

The authors studied the structure, properties and corrosion resistance in various acids of nickel-phosphorus coatings with dispersed silicon carbides after crystallization annealing under various modes. Temperatures of the beginning of crystallization after heating at speeds of 1, 5, 20 °С/min and the percentage of crystalline phases formed under isothermal conditions (nickel phosphide Ni3P and nickel) were determined. High microhardness of more than 1000 HV is achieved in a composite nickel-phosphorus coating with dispersed particles of silicon carbides during prolonged low-tempera­ture annealing, accompanied by crystallization with formation of already insignificant (10 %) amounts of Ni3P. The revealed dispersed Ni3P located both in the body and along boundaries of the grain, make the main contribution to the increment of microhardness. The yield strength and ultimate strength of coatings increase during crystallization annealing by only 12 – 15 MPa, and the elongation drops to zero, which is due to the formation of brittle Ni3P compounds. Annealing with short soaking at crystallization temperatures leads to the fact that silicon carbides exhibit a barrier effect, reducing the intensity of formation of crystalline Ni3P and corrosion resistance, while long soaking at lower crystallization temperatures forms about 70 % Ni3P, contributing to consistently high hardness and improved corrosion resistance. Corrosion resistance of composite coatings Ni-P + silicon carbides, regardless of the heat treatment modes, is maximum in acetic and orthophosphoric acids at 70 % nickel phosphide and minimum in nitric acid and its mixtures with other acids.

Microstructure and properties of magnesium/steel dissimilar metals by interlayer assisted laser welding

AbstractThe experiments of laser welding were carried out for AZ31B magnesium alloy and DP590 dual-phase steel in an overlap magnesium-on-steel configuration with interlayer addition. The interlayer elements were selected based on the calculation of thermodynamic properties and intrinsic mechanical properties, and the changes of microstructure and properties of magnesium/steel joint were analyzed. The results showed that with the addition of Sn and Al interlayers, the maximum load of the joint was 730 and 590 N, respectively, which was 2.04 times and 1.46 times higher than that without interlayer. With the addition of Al interlayer, the brittle Mg17Al12 compound was formed at the magnesium/steel interface, which limited the improvement of the mechanical performance of magnesium/steel joint. In the case of adding Sn interlayers, Mg2Sn with relatively low brittleness and Fe3Sn with a certain ductility were formed at the magnesium/steel interface, which was a vital reason that the properties of joint with Sn interlayer were higher than those with Al interlayer.

Martensitic phase transformation induced large elastic lattice strains in Nb3Sn lamellae in NiTi–Nb3Sn eutectic composite

It is known that large elastic lattice strain, which is a measure of the distortion of the interatomic bonds in solids, can influence the many physical and chemical properties of materials. However, it is not as easy to achieve ultra-large elastic strains close to their theoretical limits in bulk engineering materials as it is for nanomaterials. A breakthrough was made in a bulk NiTi–Nb composite in which Nb nanowires were induced to sustain ultra-large elastic lattice strains up to 6.5% by the martensitic transformation of the NiTi matrix via the principles of “lattice strain matching” and “collective atomic load transfer”. This study was conducted to trial out these novel concepts in an in situ NiTi–Nb3Sn eutectic composite system. The intermetallic A15-Nb3Sn is a very brittle compound and is widely used as a superconductor. Therefore, this study offers three new aspects: (i) it tests out the applicability of the principle of lattice strain matching for inducing ultra-large elastic strains in brittle materials, (ii) it investigates a material of high potential use, and (iii) it explores a novel fabrication approach for in-situ composites via eutectic solidification. The Nb3Sn lamellae in the composites were found to achieve large elastic lattice strains up to ∼2.4%, which are an order of magnitude higher than what may be expected of free-standing Nb3Sn or 3–4 times what have been achieved in Nb3Sn microfilaments embedded in other metal matrices, demonstrating the extraordinary effect of the NiTi martensitic transformation matrix. The micromechanical behaviours of lattice strain evolutions of the two phases were investigated by in-situ synchrotron x-ray diffraction analysis.

Force enhanced wire laser additive manufacturing of aluminum and titanium alloys

Brittle intermetallic compound formation is typically difficult to avoid during fusion joining of dissimilar metals. In this paper, a new approach called force enhanced wire laser additive manufacturing is proposed to join aluminum and titanium alloys. Ti6Al4V titanium alloy single track was additively fabricated on AA7075 plate successfully, through two liquid pools of the wire and the substrate, separated by a buckled unmelted part of the wire, leading to a mechanically interlocked interface. The effects of manufacturing parameters including laser power, wire feeding speed, scanning speed and initial contact force between wire and substrate on the surface morphology, internal interface microstructure and formation of intermetallic compounds were investigated through high-speed camera, spectrometer, laser topography, optical imaging, SEM imaging, XRD characterizations along with numerical simulations at different scales. And the maximum tensile strength reached 380 MPa in the tensile test. The experimental and numerical results indicate that the thermal modulation approach can effectively control the formation of brittle compounds between titanium and aluminum alloys and that the initial contact force ensures a good bond between the two metals.

Cold consolidation and coercivity enhancement in Sm2Fe17N3 magnets by high-pressure torsion

Sm2Fe17N3 coarse powder was directly consolidated into a disc magnet by the high-pressure torsion technique. The huge superimposed hydrostatic pressure (10 GPa) made it possible to apply a large amount of plastic deformation to the disc as well as the powder particles of the brittle Sm2Fe17N3 compound at room temperature. This large deformation brought about grain subdivision inside powder particles and enabled to produce a bulk magnet having the coercivity of 5.7 kOe from the coarse powder having the coercivity of 1 kOe without reducing the particle size. It was clarified that those grain subdivision events are accompanied by the motion of dislocations confined in non-basal planes. Synchrotron X-ray diffractometry was also performed and revealed that too large strain, however, results in the disappearance of the hard magnetic Sm2Fe17N3 phase and the eventual loss of the coercivity.

Tellurium Treatment for the Modification of Sulfide Inclusions and Corresponding Industrial Applications in Special Steels: A Review

Tellurium treatment is used to control the morphology of manganese sulfide (MnS) inclusions, reduce the mechanical anisotropy, and improve the machinability of sulfur‐bearing steels, such as free‐cutting steels, super free‐cutting steels, medium‐carbon microalloyed steels, and die steels. The boiling point of tellurium is low, and it is mainly added to steel in the form of fine particles wrapped in a cored wire. In steels, tellurium mainly exists in the form of Mn(S, Te) inclusions or MnTe–MnS composite inclusions. The strength of MnS inclusions is increased through tellurium doping; thus, the aspect ratio of sulfide after hot working is significantly decreased through tellurium treatment. However, the tellurium content in steel should not be too high; otherwise, brittle compounds will form and cause embrittlement, particularly in high‐alloyed steels. The Te/S mass ratio is considered an important factor in tellurium treatment. When the Te/S mass ratio in steel is 0.2, the aspect ratio of the as‐cast sulfide could be controlled within the optimal range. During steelmaking, the yield of Te can be improved by reducing the basicity of the slag and decreasing the time of Te evaporation. Through data‐driven material design, Te treatment technology undergoes broader development.

Effects of the Mn–Co spinel coating on BaZr0.1Ce0.7Y0.1Yb0.1O3-δ/AISI 441 reactive air brazed joint: Microstructure, strength, and stability

Reactive air brazing (RAB) holds great potential for joining BaZr0.1Ce0.7Y0.1Yb0.1O3-δ (BZCYYb) electrolytes with stainless steel interconnects. But this technique inevitably results in many brittle compounds along the BZCYYb interface and excessive oxidation at the steel interface. Herein, we successfully address the above issues by introducing the Mn–Co spinel coating. The coating prevents the reaction of Cr with the electrolyte and reduces brittle compounds along the BZCYYb interface, thereby elevating the joint strength by 31%. Also, it completely separates CuO and the stainless steel, thus inhibiting the excessive oxidation on the steel surface. Furthermore, the coating remains dense in both oxidizing and reducing atmospheres at 600 for 300 h, significantly enhancing the long-term stability of joints.

Joining of titanium—copper TA2/T2 bimetallic sheet by double side laser—TIG welding

Abstract In this paper, laser—tungsten inert gas (TIG) hybrid welding of TA2 titanium alloy and T2 copper alloy dissimilar joint has been performed using BCuP-2 wire as filler metal. A new welding process for TA2/T2 joining was introduced on the basis of the controlling the formation of Ti–Cu intermetallics in the joint. One process was two-pass welding involving creation of a joint with one laser weld and one TIG weld separated by remaining unmelted TA2/T2 interface. The influence of the hybrid welding process on the microstructure of the interfacial intermetallic compounds, and tensile strength of joints was investigated. The grain size of the TA2 fusion weld became larger after welding, forming acicular α martensite structure. The metallurgical combination between TIG weld and T2 base metal was good, and the TIG weld was mainly composed of α-Cu solid solution and a fine layered structure. However, a reaction layer containing α-Cu + α-Ti with an average width of about 30 μm was formed at the interface between the TIG weld and TA2 base metal, and fracture occurred along the TA2 weld and the interface of the reaction layer during tensile testing. A large number of Ti–Cu brittle compounds were avoided in joints, and the maximum tensile strength reached 610 MPa.

The first-principle study on structural, mechanical, electronic and optical properties of half-metallic CaMSi2O6 (M= Co, Fe, Mn) clinopyroxenes

Ca-based pyroxene structures have gained significant attention due to the higher abundances of calcium in the earth's crust and relatively easy synthesis process. Here, we have analyzed the structural, mechanical, elastic, thermal, and optoelectronic properties of CaMSi2O6 (M = Co, Fe, Mn) pyroxene structures in the monoclinic phase using the first-principles density functional theory (DFT) approach using CASTEP code. The lattice constants of the simulated structures in ferromagnetic (FM) orientations using GGA-WC and GGA-PBSOL were consistent with the available experimental data. Using the Born stability criteria, these structures are considered mechanically stable. These are elastically anisotropic and brittle compounds. The melting temperatures are in the order of 103 K which symbolizes these as potential candidates for high-temperature applications. The band structure alongside the electronic density of states at the Fermi level reveals half metallicity of these structures. CaMnSi2O6 structure has a maximum half-metallic gap of around 4.60 eV. The remaining two structures have an indirect band gap in the visible photon range given as 3.14 eV, and 2.65 eV for CaCoSi2O6, and CaMnSi2O6, respectively. Observing optical and electronic properties shows that the compound holds a promising future to be utilized in the optoelectronic and plasmonic fields.

Effect of Zirconium micro-addition and multi-pass friction stir processing on microstructure and tensile properties of Mg–Zn–Si alloys

The aim of this study is to investigate the microstructure and tensile properties of Mg-0.5Zn-0.2Si-XZr (X: 0, 0.25, 0.5 wt.%) in the as-cast and multi-pass friction stir processed (FSPed) conditions. Micro addition of Zr element resulted in the average grain size (AGS) reduction from 1.65 ± 0.3 mm in Mg-0.5Zn-0.2Si alloy to less than 700 μm through the formation of Zr-rich particles evenly distributed in the structure and constitutional supercooling effect. However, the refinement efficiency of Zr was reduced by the formation of Si-containing intermetallic phases through the Si poisoning effect. Thus, agglomeration of these brittle compounds, specifically at the grain boundaries, resulted in quasi-brittle fracture mode in the as-cast samples. On the other hand, applying the FSP on Zr-free alloy improved both microstructure and mechanical properties due to grain refinement and porosity content reduction. In other words, in the optimum condition, the AGS reduced to about 5 μm and yield strength (YS), ultimate tensile strength (UTS) and total elongation percentage (EL%) improved up to 70%, 90%, and 566%, respectively, compared to the as-cast sample. On the other hand, in the Zr-modified alloys, the fragmentation and even redistribution of Zr-rich and Si-rich phases, particularly after the 2nd FSP pass, enhanced the dynamic recrystallization (DRX) through the particle stimulated nucleation (PSN) mechanism and restricted the grain growth through the Zener pinning effect. Therefore, the AGS of 2 ± 0.1 μm, UTS of 182 Mpa, and EL of 36% were achieved.

Theoretical study of the interaction of lactose with collagen, the electronic and mechanical properties of crystalline lactose

We studied elastic and electronic properties of α- and β-lactose crystals within the framework of density functional theory with van der Waals interactions. The calculated values of lattice parameters have good agreement with the experimental data. The interaction energies of α- and β-lactose molecules with collagen protein were also calculated, which are equal to 4.2 and 4.1 kcal/mol, respectively. Complete set of elastic constants for α- and β-lactose were calculated. It has been established that mechanical properties of these crystals are different. Our calculations predict that α-lactose is ductile compound, while β-lactose is brittle compound. Topological properties of hydrogen bonds of the crystals were studied using the quantum theory of atoms in molecules (QTAIM). Thus, the differences between the α- and β-lactose molecules are manifested in the molecules interaction in the crystal resulting in the differences of macrocharacteristics of these crystals.

First-principles study of elastic, electronic and optical properties of Rb1-xCsxMgH3 and Cs1-yRbyMgH3 perovskite hybrides

Density functional theory was applied to further explore the properties of RbMgH3 and CsMgH3 doped with alkali metals. Two doping configurations were examined, RbMgH3 with Cs and CsMgH3 with Rb. According to elastic studies, RbMgH3 and CsMgH3 can largely withstand shear deformation. In addition, CsMgH3 has higher mechanical strength and hardness and is considered as a brittle compound, while RbMgH3 is the most rigid perovskite. On the other hand, the doping of Cs and Rb affects the wide bandgap electronic structure, absorption coefficient and reflectivity of RbMgH3 and CsMgH3, respectively, in a reduced way. The obtained results exhibit that RbMgH3, Rb0.9643Cs0.0357MgH3, CsMgH3 and Cs0.9584Rb0.0416MgH3 are potential candidates for optoelectronic devices in the ultraviolet (UV) region.

Theoretical prediction of mechanics, transport, and thermoelectric properties of full Heusler compounds Na2KSb and X2CsSb (X=K,Rb)

Full Heusler compounds have become a research hotspot in the thermoelectric (TE) field, because they have the remarkable electronic properties and high-TE power factor. Nevertheless, the inherent high thermal conductivity ${\ensuremath{\kappa}}_{L}$ hinders their further application as TE device. Hence, we investigate the mechanical, transport, and thermoelectric properties in ${\mathrm{Na}}_{2}\mathrm{KSb}$ and ${\mathrm{X}}_{2}\mathrm{CsSb}$ (X = K, Rb) with eight valence electrons per formula unit (f.u.) by using the first-principles calculations combined with self-consistent phonon (SCP) theory, compressive sensing (CS) techniques, and Boltzmann transport equation (BTE). Due to the strong three phonon scattering combined with small phonon group velocity, we obtain the ultralow lattice thermal conductivities. An evaluation of their mechanical properties reveals that they are all brittle compounds, and ${\mathrm{Rb}}_{2}\mathrm{CsSb}$ has the strongest elastic anisotropy. To capture rational electron transport properties, we include the effects of the acoustic deformation potential (ADP) scattering, polar optical phonon (POP) scattering, and ionized impurity (IMP) scattering on the electron relaxation time. Finally, a high p-type $\mathit{ZT}$ values of 2.74 (2.48) at 600 (900) K are captured in the cubic ${\mathrm{K}}_{2}\mathrm{CsSb}$ $({\mathrm{Na}}_{2}\mathrm{KSb})$. These findings not only help us to comprehensively understand the physical properties of full Heusler compounds with eight valence electrons per f.u., but also support them as potential candidates for thermal management and thermoelectric applications.

Understanding the microstructure evolution mechanism and the microstructure-strength correlations of Ti3SiC2/Ti2AlNb joint brazed with AgCu interlayer

Herein, a Ti3SiC2 ceramic was brazed to a Ti2AlNb alloy using an AgCu foil. The effect of brazing parameters on the microstructure of the brazed joint was investigated. Through careful characterizations of the interfacial reaction products, the microstructure evolution mechanism of the brazed joint was clarified. The unique crystal structure of the Ti3SiC2 phase leads to the effortless de-intercalation of Si atoms. The de-intercalated Si atoms react with Ti atoms, which dominate a series of complex interfacial reactions. The influence of brazing temperature on these interfacial reactions is strong. Maximum shear strength of 89 MPa was achieved when the joints were brazed at 860 °C for 20 min. A sound joint benefits from the detachment of Ti–Si–Cu interfacial reaction layers from the ceramic surface, the mutual diffusion zone inside the Ti3SiC2 ceramic, and moderate TiCuSi and Ti5Si3 brittle compounds in the brazed seam.

Low cycle fatigue behavior of zirconium–titanium–steel composite plate

The low cycle fatigue behavior of zirconium–titanium–steel composite plate under symmetrical and asymmetric stress control was studied. The effects of mean stress and stress amplitude on cyclic deformation, ratcheting effect and damage mechanism were discussed in detail. The results show that under symmetric stress control, the forward ratcheting deformation is observed. Under asymmetric stress control, the ratcheting strain increases rapidly with mean stress and stress amplitude increasing. Under high stress amplitude, the influence of mean stress is more significant. In addition, by studying the variation of strain energy density, it is found that the stress amplitude mainly promotes the fatigue damage, while the mean stress leads to the ratcheting damage. In addition, fracto- graphic observation shows that the crack initiates in the brittle metal compound at the interface, and the steel has higher resistance to crack propagation. Finally, the accuracy of life prediction model considering ratcheting effect is discussed in detail, and a high-precision life prediction model directly based on mean stress and stress amplitude is proposed.

Titanium-modified plasma nitriding layer and enhanced properties for 42CrMo steel

In order to obtain a nitriding layer with thicker ductile diffusion layer and thinner brittle compound layer, plasma nitriding with titanium addition was carried out at 540 °C for 4 h for 42CrMo steel, the characteristic of titanium modified nitriding layer and the enhanced properties were systematically investigated by optical microscope (OM), scanning electron microscope (SEM), XRD, hardness tester and wear tester etc. The results show that titanium addition can effectively modify the characteristics of nitrided layer, and thus a plasma nitrided layer owning thicker ductile diffusion layer and thinner brittle compound layer and higher surface hardness can be obtained. Titanium addition can significantly decrease the compound layer and increase the effective hardening layer, and also greatly enhance the surface hardness, especially with the optimal amount of 0.8 g, the compound layer can be reduced from 19 μm to 10 μm, while the effective hardening layer can be increased from 225 μm to 370 μm. And the surface hardness can be enhanced from 703HV0.05 to 889HV0.05, more importantly, both wear resistance and toughness can be greatly promoted by the novel titanium modified plasma nitrided layer, attributed to the formation of dispersedly distributed TiN particles with very high hardness in the nitriding layer.