Nanoparticle Strengthening Research Articles

Advance on rock-breaking cutter steels: A review of characteristics, failure modes, molding processes and strengthening technology

Rock breaking has always been a challenging problem that must be solved in projects such as excavating mountains, drilling wells, and constructing railways. Among the rock-breaking cutter steels, AISI H13 steel and wear-resistant high manganese steel have become the best choices. From the characteristics and failure modes of the two, rock-breaking cutter steels should simultaneously have high strength, high toughness and high wear resistance to avoid short-term fracture/damage and cost increase. Analyzing the problems existing in the molding process of rock-breaking cutter steels such as die casting, forging, and hot stamping, traditional strengthening technologies such as alloying optimization, heat treatment, and surface treatment can achieve certain performance enhancement. After reaching the limits of traditional strengthening technologies, a series of nanoparticle strengthening technologies came into being. The selection, addition amount, and addition method of nanoparticles all affect the microstructure, mechanical properties and wear. To this end, this article summarizes the research progress and challenges of rock-breaking cutter steels, and discusses traditional strengthening technologies and mainstream nanoparticle strengthening technologies. It provides a reference for the future development of high-quality and high-performance rock-breaking cutter steels, with aim to simultaneously expand their application potentials to other fields.

Unique Yttria Nanoparticle Strengthening in an Inconel 718 Superalloy Fabricated by Additive Manufacturing

AbstractOxide dispersion strengthened (ODS) nickel (Ni)‐based superalloys are advanced materials known for their outstanding tensile and creep performance at temperatures exceeding 1000 °C. Nevertheless, their conventional synthesis presents a longstanding challenge in cost‐effectively producing intricate components for critical applications. In this work, electrostatic self‐assembly (ESA) of powders with the laser powder bed fusion (LPBF) process are successfully combined to produce yttria ODS Inconel 718 (IN718) alloy for the first time. This approach demonstrates a significant contribution of yttria to the strength of IN718 after the solid solution heat treatment, as evidenced by ≈50% improvement in room temperature yield strength with a 0.5 wt.% yttria addition. The addition of yttria by this process leads to a heterogeneous microstructure. This heterogeneous microstructure comprises two distinct grain areas with varying amounts of yttria nanoparticles and dislocation storage. The results show that the yield strength increase can be predicted by the combination of both Y2O3 dispersion strengthening and dislocation strengthening mechanisms. These findings offer an effective approach to tailor heterogeneous microstructures, unlocking new opportunities for cost‐effectively producing high‐performance ODS Ni‐based superalloy products with excellent mechanical properties.

Laser powder bed fusion of Al–Mg–Zr alloy: Microstructure, mechanical properties and dynamic precipitation

A Sc-free and high-plasticity Al-4.8Mg-1.6Zr aluminum alloy was densified via laser powder bed fusion. The microstructure features a typical bimodal grain structure, with abundant L12-Al3Zr particles about 100 nm distributed. The yield strength (YS) of 449 ± 4 MPa, ultimate tensile strength (UTS) of 449 ± 5 MPa, and the elongation to failure (EL) of 15.1 ± 1.9% are obtained after peak aging. In addition to solid solution strengthening, grain boundary strengthening and nanoparticle strengthening, the long-range stacked ordered 9R phase associated with high content Mg and Zr also contributes to strengthening. Besides, the difference in strain distribution between coarse and fine grain zones causes deformation-induced hardening. Low-temperature dynamic precipitation is observed in this Al–Mg–Zr alloy for the first time. The deformation-induced hardening and dynamic precipitation improve the strain-hardening capability, consequently delaying necking instability. After peak aging treatment, the number of Al3Zr particles with strong high-temperature stability increases, inhibiting grain coarsening and enhancing the precipitation strengthening effect. The excellent strength-ductility trade-off of the printed Al–Mg–Zr without expensive Sc element gives it a broad application prospect in economical and large-scale additive manufacturing.

Achieving thermally stable nanoparticles in chemically complex alloys via controllable sluggish lattice diffusion

Nanoparticle strengthening provides a crucial basis for developing high-performance structural materials with potentially superb mechanical properties for structural applications. However, the general wisdom often fails to work well due to the poor thermal stability of nanoparticles, and the rapid coarsening of these particles will lead to the accelerated failures of these materials especially at elevated temperatures. Here, we demonstrate a strategy to achieve ultra-stable nanoparticles at 800~1000 °C in a Ni59.9-xCoxFe13Cr15Al6Ti6B0.1 (at.%) chemically complex alloy, resulting from the controllable sluggish lattice diffusion (SLD) effect. Our diffusion kinetic simulations reveal that the Co element leads to a significant reduction in the interdiffusion coefficients of all the main elements, especially for the Al element, with a maximum of up to 5 orders of magnitude. Utilizing first-principles calculations, we further unveil the incompressibility of Al induced by the increased concentration of Co plays a critical role in controlling the SLD effect. These findings are useful for providing advances in the design of novel structural alloys with extraordinary property-microstructure stability combinations for structural applications.

Effects of annealing and extrusion on the microstructure and tensile properties of ultrafine-grained Al fabricated by spark plasma sintering

ABSTRACT Ultrafine-grained Al samples were fabricated by spark plasma sintering (SPS) of a mechanically milled nanocrystalline powder. The effects of annealing and extrusion on the microstructure and tensile properties of the as-SPSed samples were investigated. Annealing removed the nanopores and caused significant coarsening of Al grains in the interparticle boundary (IPB) regions, leading to the formation of a heterogeneous structure consisting of coarse grains, ultrafine grains and Al4C3/Al2O3 nanoparticles. Hot extrusion also eliminated the nanopores and resulted in the formation of a heterogeneous structure containing enhanced volume fraction of ultrafine grains and finer nanoparticles. These microstructural changes rendered a much improved YS and UTS of 251 and 288 MPa, respectively, and excellent tensile ductility (elongation to fracture: 12.7%). The improvement in mechanical properties can be attributed to grain boundary and nanoparticle strengthening, strain delocalisation of the heterogeneous structure and improvement of the bonding strength of IPBs.

The microstructures and mechanical properties of a 5vol%SiC/AA2024 nanocomposite fabricated by powder metallurgy

A 5vol%SiC/AA2024 nanocomposite was prepared by a powder metallurgy routine involving high energy ball milling (HEBM), spark plasma sintering (SPS) and hot extrusion. The microstructures and mechanical properties of the 5vol%SiC/AA2024 nanocomposite samples prepared using different HEBM and SPS times were investigated in detail. It was found that increasing the milling time from 12 to 24 h caused refinement of Al grains and better dispersion of SiC nanoparticles, leading to a significantly increase of hardness and strength. Increasing the SPS time from 5 to 10 min helped to improve the quality of interparticle bonding, and resulted in grain growth and consequently the formation of a bimodal microstructure which is beneficial for the improvement of ductility. Optimized tensile mechanical properties were achieved in a 5vol%SiC/AA2024 nanocomposite with ball milling time of 24 h and SPS time of 10 min, with its yield strength, ultimate tensile strength and elongation to fracture being 463 MPa, 626 MPa and 4.4%, respectively. Based on the analysis of the contributions of different strengthening mechanisms to the strength, nanoparticle strengthening and grain boundary strengthening made the majority of the contributions to the improved strength of the 5vol%SiC/AA2024 nanocomposite.

Understanding material behaviour of ultrafine-grained aluminium nano-composite sheets with emphasis on stretch and bending deformation

Abstract This study investigates the forming limits of cryo-rolled Ultrafine Grained (UFG) aluminium sheet for loading conditions relevant to sheet metal forming. It is shown that a combination of nano-particle strengthening with an annealing heat treatment enables the production of cryo-rolled UFG aluminium with up to 12 % higher material strength and 20 % higher formability compared with the unreinforced UFG condition. While nano-particle strengthening does not significantly influence the tensile ductility, it reduces the bend fracture limit by over 50 % due to an increased dislocation density and a diffuse sub-grain structure. The level of the forming limit curves (FLD) of all UFG materials was up to 5 times higher than their uniform tensile elongation and hardening index; this is attributed to a high strain-rate sensitivity, which increased with annealing heat treatment. In roll forming, the UFG aluminium showed similar material behaviour and shape defects as observed for conventional sheet metals in previous studies. However, given the reduced bend fracture limits observed with nano-particle addition, this study suggests that roll forming may not be a suitable manufacturing solution for nano-particle strengthened UFG sheet metal.

High as-cast strength die-cast AlSi9Cu2Mg alloy prepared by nanoparticle strengthening with industrially acceptable ductility

High as-cast strength die-cast AlSi9Cu2Mg alloy was achieved with industrially acceptable ductility, via the addition of titanium diboride nanoparticles. The main intermetallic compounds in the die-cast AlSi9Cu2Mg alloy were identified as θ–Al2Cu and Q–Al5Cu2Mg8Si6 phases. The Fe-rich compound formed in the present die-cast alloy with a high Mn/Fe ratio of 3:1 was determined as the BCC structured α–Al15(Fe,Mn)3Si2 phase with a lattice parameter of a = 1.2702 nm, and the Fe-rich compound had highly faceted morphology with {110} surface termination. The Al matrix phase in the die-cast AlSi9Cu2Mg alloy was refined by ∼65% from 18.1 μm to 6.4 μm, after adding 3.0 wt% titanium diboride nanoparticles. The titanium diboride nanoparticles in the alloy showed coherent interface with the Al matrix, with the (11-1) lattice face of Al parallel to the (0001) lattice face of titanium diboride. The as-cast AlSi9Cu2Mg alloy containing 3.0 wt% titanium diboride nanoparticles exhibited the high yield strength of 233 ± 3 MPa and the tensile strength of 398 ± 7 MPa, as well as the industrially acceptable elongation of 4.8 ± 0.7%, and it showed at least 23% improvement in the as-cast yield strength over the existing die-cast Al alloys. The strengthening by nanoparticle and coherent interface (∼32 MPa) was higher than that by the refining of Al matrix (∼10 MPa). The addition of titanium diboride nanoparticles also affected the fracture of the die-cast AlSi9Cu2Mg alloy, and cracks were prone to form in the Q and Fe-rich compounds, after the addition of titanium diboride nanoparticles.

Effects of Cu addition on the microstructure and properties of the Al–Mn–Fe–Si alloy

Abstract Heat exchanger materials with high strength and thin thickness are highly required due to the increasing demands of weight reduction and fuel economy of the automobile. In this work, 0.5 wt% Cu was added to an Al-1.5Mn-0.3Fe-0.6Si (wt.%) alloy to improve the strength. The microstructure, mechanical properties, and electrochemical properties of the tested alloys were systematically investigated. The results suggest that part of Cu is dissolved into the Al matrix, and the balance is incorporated into the Al(Mn,Fe)Si particles. Cu addition improves the strength at the expense of deteriorating the pitting corrosion resistance. On the one hand, the improved strength derives from enhanced solid solution hardening and increased nanoparticle strengthening. On the other hand, the incorporation of Cu in the Al(Mn,Fe)Si intermetallic particles increases the potential difference between the particles and the Al matrix, resulting in the deteriorated pitting corrosion resistance.

Developing a high-strength Al-Mg-Si-Sc-Zr alloy for selective laser melting: Crack-inhibiting and multiple strengthening mechanisms

To develop high-strength Al alloys for selective laser melting (SLM) additive manufacturing, we designed a series of Al-Mg(-Si)-Sc-Zr alloys and additively manufactured them using atomized alloy powders. In the absence of Si, the developed Al-xMg-0.2Sc-0.1Zr (x = 1.5, 3.0 and 6.0 wt%) alloys are all susceptible to hot cracking and the average crack density increases with increasing Mg content. The addition of 1.3 wt% Si into the Al-6Mg-0.2Sc-0.1Zr alloys effectively inhibits hot cracking during SLM and simultaneously refines the microstructure, and thus leading to enhanced mechanical properties in the as-printed samples. By further fine-tuning the alloy compositions, we designed a new alloy Al-8.0Mg-1.3Si-0.5Mn-0.5Sc-0.3Zr. This new alloy demonstrates significantly refined microstructure consisting of submicron cells with coherent Al3(Sc,Zr) nano-particle (2–15 nm) residing in the cell and intergranular Al-Mg2Si eutectic (Mg2Si diameter 10–100 nm). High-density stacking faults and a unique 9R phase are formed in the as-printed sample. The tensile strength and elongation of the as-printed sample are up to 497 MPa and 11%, respectively. After the aging treatment, the tensile strength reaches 550 MPa, while the ductility ranges from 8% to 17%, depending on the aging conditions. In addition to solid solution strengthening, grain boundary strengthening and nanoparticle strengthening, the high-density stacking faults also contributes to strengthening.

Carbon and nitrogen co-doping enhances phase stability and mechanical properties of a metastable high-entropy alloy

Abstract To probe the significant interstitial effects coupling with the metastability design of high-entropy alloys (HEAs), we introduced both interstitial C and N into a representative metastable HEA. The mechanical behavior of the novel C-N co-doped interstitial HEA (iHEA) with nominal composition Fe48.5Mn30Co10Cr10C0.5N1.0 (at. %) in different grain sizes has been investigated via digital image correlation (DIC) assisted tensile testing. The microstructure characteristics prior to and after tensile deformation with different local strain levels were probed by various techniques. The C-N co-doped iHEA shows a face-centered cubic (FCC) matrix without hexagonal closed packed (HCP) martensite after annealing plus the subsequent quenching, different from the reference metastable FCC-HCP dual-phase HEA without interstitials. Upon tensile deformation, dislocation slip and twinning prevail, and the new iHEA does not show phase transformation which is the primary deformation mechanism in the reference interstitial-free metastable HEA. This further confirms the enhanced FCC phase stability due to C-N co-doping. The interstitial effect coupling with the multiple strengthening mechanisms including twinning induced plasticity (TWIP) and nano-particle strengthening due to nano-sized carbonitrides leads to significantly higher yield strength (753 MPa) and ultimate tensile strength (1038 MPa) at good ductility (48.0%) compared to that of the reference interstitial-free metastable HEA (∼250 MPa, ∼850 MPa and ∼70%, respectively) at a similar grain size of ∼4 μm. Accordingly, our work demonstrates the significant capability of interstitials including C and N for tuning the phase stability and enhancing mechanical properties of HEAs.

A novel nanostructure to achieve ultrahigh strength and good tensile ductility of a CoCrFeNiMn high entropy alloy.

A CoCrFeNiMn high entropy alloy with a novel nanostructure consisting of ultrafine grains, TiO(C) nanoparticles and nanotwins has been fabricated. It achieves an ultrahigh tensile yield strength of 1507 MPa by coupling multiple strengthening mechanisms, including grain boundary strengthening, twin boundary strengthening, nanoparticle strengthening and dislocation strengthening. The work hardening ability is also improved by coupling the interactions of dislocations with nanoparticles and nanotwins during plastic deformation, leading to a good tensile ductility with a uniform elongation of 4.7%.

Architecture of high-strength aluminum\u2013matrix composites processed by a novel microcasting technique

As important lightweight structural materials, cast aluminum alloys have been largely used in the transportation and aerospace industries. In general, Al–Si-based alloys comprise more than 90% of all castings due to their excellent castability and corrosion resistance. However, even though various reinforcements have been introduced, the strength of these alloys is not that high, which severely limits their use for certain high-performance applications. Here, we report on a new strategy and technology to reinforce Al–Si alloys to increase their yield strength into the ~400–660 MPa range, a level that is 29–113% higher than that of all current cast Al–Si alloys, laboratory or commercial, and comparable to that of many high-strength steels but with ~40% lower density. By introducing continuous Ti–6Al–4V reinforcements into the Al–Si matrix through a novel microcasting process, the yield strength of the resulting alloy can be enhanced to between 4 and 6 times higher than that of the pure Al–Si alloy. The extraordinary reinforcing effect originates from the occurrence of multiscale strengthening mechanisms, including macroscale compound strengthening (the rule of mixtures amended by crack arrest mechanism), mesoscale strain-gradient strengthening, and microscale interface-affected-zone and nanoparticle strengthening. The core principle of our material design is to make all components of the composite fully participate in plastic (compatible) deformation, and thus, continuous reinforcements, instead of discrete reinforced structures (e.g., particles, whiskers, and short fibers), were introduced into the Al–Si alloy. Combined with 3-D printing technology, the present microcasting process can realize strengthening at the designed position by architecting specific reinforcements in the matrix.

Grain growth and strengthening mechanisms of ultrafine-grained CoCrFeNiMn high entropy alloy matrix nanocomposites fabricated by powder metallurgy

Ultrafine-grained CoCrFeNiMn high entropy alloy matrix nanocomposites reinforced by nanoparticles were fabricated by thermomechanical consolidation of high energy mechanically milled powders. TiO(C) nanoparticles in the CoCrFeNiMnTi0.15 sample make the FCC matrix grains clearly finer than those in the CoCrFeNiMnNb0.1 sample with NbC and (Cr, Mn)3O4 nanoparticles (average grain size: 503 ± 184 vs 778 ± 274 nm). Quantitative analysis reveals that drag force for grain growth during consolidation in the CoCrFeNiMnTi0.15 sample is higher than that in the CoCrFeNiMnNb0.1 sample due to the higher Zener force from the TiO(C) nanoparticles. The microstructural difference renders the yield strength of the CoCrFeNiMnTi0.15 sample to be almost 50% higher than that of CoCrFeNiMnNb0.1 sample (1243 vs. 831 MPa). To elucidate this phenomenon, the strengthening mechanisms are systematically analyzed and a model considering grain boundary dislocation emission is established to account for the interaction between grain boundary strengthening and nanoparticle strengthening. This model explains the different effects of NbC, (Cr, Mn)3O4 and TiO(C) nanoparticles, and estimates the yield strength better than the existing models.

Combined effect of nanoparticle and grain refinement on yield stress of nanocomposite

ABSTRACTConsidering a high resistance to plastic deformation as a major requirement for many applications of modern engineering materials, the combined effects arising from grain refinement and second-phase nanoparticle on the enhanced strengthening of nanocomposites are predicted. In this work, we investigate when the external critical stress is applied, the splitting transformation of grain boundary dislocations (GBDs) within the double ended pile-ups at TJs (carriers of GB sliding) occurs, which initiates at the onset of yielding and serves as a channel of plastic deformation. In the framework of the model considered, the total energy change characterising this process is attained using the complex potential method for plane elasticity. The influence of the material elastic dissimilarity, lattice misfit strain, the radii of nanoparticle and grain size, geometric parameters of triple junctions (TJs), pile-up number of GBD dipoles and the interface stress on the energy and critical conditions for such a splitting is revealed quantitatively, and then the contribution of each factor to yield stress of nanocomposite has been evaluated more deeply. The theory predicts that grain refinement and second-phase nanoparticle strengthening interact significantly, strongly influence the GBD splitting and then yield stress. It contributes to understanding of the possible influence of these parameters for the effects of microstructure on the deformation behaviour of nanocomposites, which can help guiding the development of nanocomposite with enhanced strength and ductility.HighlightsEffects of grain refinement and nanoparticle on splitting of GBD are predicted.Splitting of GBDs within double ended pile-ups (carriers of GB sliding) occurs.Analytic solution of energy change characterising this process is derived.Reveal quantitatively energy and critical conditions for initiating these processes.Grain refinement and nanoparticle interact significantly, impacting yield strength.Characterise effect of microstructure interactions on predominant mechanism.

Effects and distribution of TiC on the nanoparticle strengthening A-TIG welded AZ31 magnesium alloy joints

AZ31 magnesium alloy sheets were A-TIG welded using mixed activating flux, which contained different ratio of TiC nanoparticles (TiCp) and TiO2 powder, as surface coating. From mechanical test, the values of ultimate tensile strength and microhardness increased from 120.2 MPa to 181.7 MPa, 46.4 HV to 84.2 HV, respectively, which mainly resulted from the grain boundary strengthening of α-Mg and the dispersion strengthening of TiCp. The theoretical calculation suggested that the improvement of the yield strength was mainly the combination of the Hall-Petch and Orowan strengthening mechanisms, and the mismatch strain caused by different coefficient of thermal expansion between the matrix and the particles. Numerical simulation showed that the TiCp had a centralized tendency toward middle and bottom part of welding pool and was confirmed by the micro-zone microhardness test results in the fusion zoon.

Effects of cerium and SiC mixed particles on nanoparticle strengthening activated TIG-welded AZ31 alloy joints

Abstract

Strengthening effects and thermal stability of the ultrafine grained microstructure of a nickel base superalloy at room and elevated temperatures

An ultrafine grained (UFG) nickel base superalloy doped with 5 vol.%Y2O3 nanoparticles, Alloy 718-5 vol.%Y2O3, was fabricated by a powder metallurgy route which combines high energy mechanical milling of Alloy 718 machining chips, spark plasma sintering, hot extrusion and heat treatment, and its microstructure and mechanical properties at room temperature and 650 °C were studied. The study showed that the Y2O3 nanoparticles reacted with Al from the base alloy and transformed to Y4Al2O9 nanoparticles (average diameter: 12.5 nm) which were stable during heat treatment at 970 °C (0.78Tm, where Tm is the solidus temperature of the alloy in K). As a result of the high thermal stability of Y4Al2O9 nanoparticles and their effective pinning of the grain boundaries, the UFG microstructure (average grain size: 179 nm) of the alloy was stable during heat treatment. Grain boundary and nanoparticle strengthening rendered the heat treated Alloy 718-5 vol.%Y2O3 alloy with a notable room temperature tensile yield strength of 1870 MPa. It was demonstrated that the grain boundary strengthening effect associated with the UFG microstructure was still significant at 650 °C, but clearly decreased from its level at room temperature. The grain boundary strengthening and nanoparticle strengthening effects which are likely to be independent of test temperature sustain a reasonably high tensile yield strength of 800 MPa at 650 °C, despite the absence of γ′ and γ″ precipitates in the UFG microstructure.

Analysis of dry sliding wear behavior of the nano composites using statistical methods with an emphasis on temperature effects

The objective of the present work is to understand the effects of speed, load, distance and temperature on the dry sliding wear behavior of Al/B4C, Al/B4C/MoS2 nanocomposites and the Al alloy. The nanocomposites and the alloy were fabricated by the stir casting technique and tested in a pin on disc wear testing apparatus. The parameters considered were: load – 10–50 N, speed – 0.942–4.713 m/s, sliding distance – 500–1500 m, temperature – 50–90 °C. The central composite design was used to design the experiments. The response surface methodology was used to identify the important factor affecting the wear resistance and to study the interaction effects among the factors. The temperature was found to be a primary factor affecting the wear resistance. The interactions between the load and the speed and, the load and the distance were found to be significant. Excellent correlation existed between the predicted and the experimental results within 2.5% error. The confirmatory experiments proved the adequacy of the model with a reasonable accuracy. The worn surface of the nanocomposites and the alloy were characteristised using the scanning electron microscope equipped with energy dispersive spectroscopy and X-ray diffraction techniques to understand the prevailing wear mechanisms for the selected conditions. The stable tribofilm and the nano particle strengthening reduced the intensity of abrasion, delamination, oxidation and third body wear mechanisms and keep the wear under control in the nanocomposites. Particularly, the Al/B4C/MoS2 hybrid nanocomposites showed the best wear resistance due to the formation of MoS2 rich tribofilm.

Plastic-deformation-driven SiC nanoparticle implantation in an Al surface by laser shock wave: Mechanical properties, microstructure characteristics, and synergistic strengthening mechanisms

Laser shock-wave-driven nanoparticle implantation (LSWNI) in alloys is a novel surface strengthening technique based on plastic deformation induced by laser shock processing and the excellent properties of hard-phase nanoparticles. In the present work, 50–100 nm silicon carbide (SiC) nanoparticles were successfully implanted into commercially pure aluminum (Al) substrates under the effect of a laser shock wave. After the implantation, stable nanoparticle-reinforced layers were fabricated, and their microstructural response and grain refinement were characterized by X-ray diffraction (XRD), focused ion beam (FIB), and transmission electron microscopy (TEM). In addition, the mechanical properties, including residual stress, nanohardness, elastic modulus, and wear resistance, were investigated. Experimental results showed that Al samples subjected to LSWNI exhibited superior mechanical properties because of the good combination between the gradient microstructure induced by plastic deformation and the gradient distribution of the implanted SiC nanoparticles along the depth direction. Therefore, the overall strengthening effect generated by the LSWNI process can be described as two different modes: (i) the gradient microstructure induced by plastic deformation contributed mainly to the enhancement of residual stress and nanohardness, and (ii) the gradient distribution of the implanted SiC nanoparticles was dedicated primarily to the improvement of the wear resistance. As indicated by the strengthening effect during the LSWNI process, three competing strengthening mechanisms, namely, SiC nanoparticle strengthening, refined grain strengthening, and dislocation strengthening, existed in the gradient-reinforced layers. The detailed contribution of each mechanism to the overall properties of the reinforced layer was determined using the modified Clyne computational model and was described herein. Finally, the wear mechanism of the reinforced layer fabricated by the LSWNI process is revealed.