Vickers Indentation Tests Research Articles

The Cr/Cr2N multilayer coating with high load-bearing capacity and thermal shock resistance

By utilizing the multi-arc ion plating (MAIP) technique, multilayer coatings with varying Cr/Cr2N ratios and uniform thicknesses were deposited onto a nitrided Cr–Ni–Mo–V steel substrate. The evolution of microstructure and mechanical properties was characterized using scanning electron microscopy, X-ray diffraction, and micro-Vickers hardness testing. The load-bearing capacity of the multilayer coatings with varying modulation ratios was comprehensively evaluated through Vickers indentation tests with a 10-kgf load, Rockwell hardness testing with a 150-kgf load, and scratch tests with loads of 60 and 100N. The coating with a Cr/Cr2N layer modulation ratio of 0.2/0.4 μm exhibited a hardness of 1385 HV and an adhesion strength of 91N. Under a 10kgf load, this coating also demonstrated excellent fracture toughness, and did not exhibit any radial cracks in the Vickers indentation. Subsequently, a thermal shock test, involving quenching from 900°C water to 25°C, was conducted on the coating with the best comprehensive performance. The multilayer coating with high load-bearing capacity could withstand 52 thermal shock cycles before delamination occurred. Failure analysis further confirmed that the multilayer coating with enhanced load-bearing capacity effectively resisted thermal shock.

Glass-ceramics and molybdenum doping synergistic approach for Nasicon-type solid-state electrolytes

Advancing energy density, enabling lithium metal anodes, and ensuring unparalleled safety and operational reliability in lithium batteries hinge on advancing inorganic solid-state electrolytes. To overcome current impediments, we present an innovative approach that integrates glass-ceramics with a pioneering new Nasicon strategy involving molybdenum doping. In the conducted study, a series of 14Li2O-9Al2O3-38TiO2-(39-x)P2O5-xMoO3 glasses, denoted as LATPMox, along with their corresponding glass-ceramics (LATPMox-GC), have exhibited a promising characteristic as solid electrolytes. X-ray diffraction (XRD) analysis confirms the formation of the novel Mo-doped Nasicon phases in the glass-ceramics, as validated by Rietveld refinement. Examination of the crystallization kinetic behavior of the glasses reveals a three-dimensional nucleation process with spherical particle growth, featuring an activation energy of 165 kJ mol−1. Transmission Electron Microscopy TEM characterization aligns crystallization behavior with crystallite and distribution within the glass matrix, resulting in a compact and dense microstructure. The structural properties of the resultant phases are examined through FT-IR, Raman spectroscopy, and TEM-SEAD analysis. Vickers indentation tests were employed to assess the microscopic fracture toughness, and both the glass and glass-ceramics materials demonstrated favorable mechanical performance. Optical characterization using UV–visible absorption highlights the reduction of Mo6+ to Mo5+, likely occupying tetrahedral sites within the crystalline lattice. Impedance spectroscopy measurement showcases the effective promotion of ionic conductivity following Mo doping, reaching a total conductivity value of 5.50 × 10−5 Ω−1 cm−1 along with a high lithium transference number of 0.99 at room temperature for LATPMo2.6-GC glass-ceramic. This value is larger than that of many other glass-ceramics as well as that of the well-known lithium phosphorous oxy-nitride LiPON solid electrolyte whose ionic conductivity at RT is around 2 × 10−6 Ω−1 cm−1.

Evaluation method of dynamic indentation behavior of glass based on electromagnetic induction phenomena

AbstractContact damage of glass is one of the most crucial issues for glass products. To develop strong and tough glass products and to compare damage resistance among glass compositions, a simple method for evaluating the mechanical response of glass during contact is required not only for glass mechanists but also for glass customers and suppliers. Although it is well known that the quasi‐static Vickers indentation test is one of the simplest and most useful methods to evaluate hardness and brittleness in glass, the indentation response of glass under the indenter at higher impact velocities remains to be quantitively understood because of the difficulty of measurement and limited experimental works. In this study, therefore, the dynamic indentation behavior of soda‐lime glass is evaluated by using a lab‐made free‐drop indentation set‐up with the coils for detecting electromotive forces (EMFs). The cono‐spherical indenter made of tungsten carbide attached with a neodymium magnet was employed to generate the EMFs when the indenter passed through the coils located near the glass sample. The impact load versus indentation depth curve during the impact within a few tens of microseconds was successfully obtained both for an elastic contact and for an inelastic contact. Under an elastic condition, where no residual indent nor any cracks were left on the glass surface after the test, it is confirmed that there is almost no hysteresis in the impact load versus indentation depth curve and that the curve can be reproduced by the Hertzian analytical solution. Under an inelastic condition, on the other hand, it is found that the hysteresis in the impact load versus indentation depth curve stems from inelastic phenomena, such as plastic deformation (shear flow and/or permanent densification) and cracking. These results suggest that the dynamic indentation technique based on electromagnetic induction phenomena is a useful and effective tool for evaluating the mechanical responses of glasses during the impact.

Opportunity of ferrimagnetic (CZLF)/ferroelectric (BZT) composite materials in high frequency applications

The ferrimagnetic Zn0.35Co0.65 La0.02Fe1.98O4 (CZLF) ferrite with cubic spinel structure (space group Fd3m) was made into composite by mixing with ferroelectric Ba0.5Zr0.5TiO3 (BZT) perovskite with tetragonal structure (space group P4mm) at the mass ratio. Disk-shaped composite powder was finally heated at 1100 °C to study the structure, dielectric and ferroelectric properties. The structural characterization for synthesized samples were carried out using Fourier transform infrared and Transmission Electron Microscopy. Fourier transform infrared show the successful formation of composite samples which is also observed from x-ray diffraction pattern. In compared to their ferrite counterparts before the composite, dielectric response and ferroelectric characteristics of the composite samples are noticeably altered. Compared to the ferrite samples, the composite system exhibits a higher permittivity. In composite samples, the space charge polarization, which was primarily effective at low frequencies and high measurement temperatures, is much diminished. The mechanical properties and indentation creep of these bearing alloys were studied by Vickers indentation testing at room temperature. The remnant polarization of BZT/CZLF increases with decreasing BZT content, which may be suitable for permanent memory device applications. Graphical abstract

Application of 20% silver nanoclusters in polymethacrylic acid on simulated dentin caries; its penetration depth and effect on surface hardness

The aims of this study were: To evaluate the surface hardness of simulated dentin caries lesions treated with either silver nanoclusters (AgNCls) synthesized in polymethacrylic acid (PMAA) or 38% silver diammine fluoride (SDF), as well as observe the penetration of the treatment solutions into the simulated caries lesions. Dentin blocks 4 mm thick obtained from caries-free third molars were sectioned and then simulated caries lesions on the occlusal dentin surfaces were created. Each specimen (n = 8) was divided into four sections: (A) treated with 20% AgNCls/PMAA; (B) treated with SDF 38% (FAgamin, Tedequim, Cordoba, Argentina); (C) sound tooth protected by nail-varnish during artificial caries generation (positive control); and (D) artificial caries lesion without surface treatment (negative control). AgNCls/PMAA or SDF were applied on the simulated lesions with a microbrush for 10 s, then excess removed. The surface hardness was measured by means of Vickers indentation test. To trace the depth of penetration, up to 400 μm, of silver ions, elemental composition of the samples was observed using EDX, coupled with SEM, and measured every 50 μm from the surface towards the pulp chamber. Laser Induced Breakdown Spectroscopy (LIBS) was also employed to trace silver ion penetration; the atomic silver line 328.06 nm was used with a 60 μm laser spot size to a depth of 240 μm. Student’s-t test identified significant differences between treatment groups for each depth and the Bonferroni test was used for statistical analysis of all groups (p < 0.05). Mean surface hardness values obtained were 111.2 MPa, 72.3 MPa, 103.3 MPa and 50.5 MPa for groups A, B, C and D respectively. There was a significant difference between groups A and C compared with groups B and D, the group treated with AgNCls/PMAA achieved the highest surface hardness, similar or higher than the sound dentin control. A constant presence of silver was observed throughout the depth of the sample for group A, while group B showed a peak concentration of silver at the surface with a significant drop beyond 50 μm. The 20% AgNCls/PMAA solution applied to simulated dentin caries lesions achieved the recovery of surface hardness equivalent to sound dentin with the penetration of silver ions throughout the depth of the lesion.

Mechanical properties and oxidation behavior of (Mo,W)AlB, (Mo,Cr)AlB, and (Mo,W,Cr)AlB MAB solid solutions synthesized with spark plasma sintering

This study reports the effects of solid solution on the mechanical and oxidation behavior of MoAlB ceramics. (Mo,W)AlB, (Mo,Cr)AlB, and (Mo,W,C)rAlB were synthesized under 30 MPa at 1200 °C by Spark Plasma Sintering (SPS). Composition and microstructure were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and energy-dispersive X-ray spectroscopy (EDS). Although it was determined that the main phase was MoAlB solid solution, it was observed that binary borides such as WB were also present in the (Mo,W)AlB and (Mo,W,Cr,)AlB. Hardness was measured by the Vickers indentation test. The hardnesses of MoAlB solid solutions improved considerably compared to pure MoAlB and were obtained as 13.65, 12.72, and 13.37 GPa, respectively, for (Mo,W)AlB, (Mo,Cr)AlB, and (Mo,W,Cr)AlB. The reasons for the improvement in hardness are estimated to be grain refinement and solid solution hardening mechanism. Fracture toughnesses calculated from radial cracks formed during Vickers indentation are 6.52, 5.88, and 6.40 MPam1/2, respectively. Although crack bridging and deflection mechanisms work with solid solutions, as in pure MoAlB, the brittle binary borides in the structure did not improve fracture toughness. The oxidation test was carried out at 1200 °C for 12 h. A dense and continuous protective oxide layer was formed in all samples. The scale thicknesses of (Mo,W)AlB, (Mo,Cr)AlB, and (Mo,W,Cr)AlB are 3.2, 2.1, and 2.6 μm, respectively.

On understanding the mechanical properties and damage behavior of Cf/SiC composites by indentation method

Carbon fiber reinforced silicon carbide ceramic matrix (Cf/SiC) composites have the advantages of high temperature resistance, wear resistance, low density, high hardness as well as specific strength. They have been applied extensively in hot-end components of aerospace and braking systems of trains. Nevertheless, grappling with the anisotropy, non-homogeneity, and weak interlayer bonding of Cf/SiC composites presents a major challenge for achieving efficient and low-damage processing. This paper is primarily intended to investigate comprehensively the mechanical properties and damage behavior of Cf/SiC composites by nanoindentation and Vickers indentation tests. The behaviors of indentation damage on the longitudinal section of fiber (LSF), the cross-section of fiber (CSF) and matrix under different loads and the deflection mechanism of matrix crack were analyzed. The findings reveal a pronounced anisotropy between the radial and axial orientations of the fiber, and plastic deformation exists in the matrix. Furthermore, the matrix has the largest hardness and elastic modulus, while the LSF displays the lowest values among the composites. The main forms of indentation damage on the LSF are fiber crack, fiber peel off, fiber cocked up and squamous crack. The main manifestations of indentation damage on CSF are fiber crushing and fiber debonding, with the total surface damage area being comparatively limited. The fiber orientation and interface are influential factors in the crack propagation path of matrix. Notably, the fibers effectively inhibit the crack propagation of the matrix. This investigation provides valuable theoretical guidance for the formation mechanism and suppression strategy of machining damage in Cf/SiC composites.

Mechanical Properties and Toughening Mechanisms of Promising Zr-Y-Ta-O Composite Ceramics

ZrO2-YO1.5-TaO2.5 (ZYTO) composite ceramics are considered to be a candidate for next-generation thermal barrier coatings (TBCs) due to their excellent thermal stability and low thermal conductivity in high temperatures; however, the mechanical properties and fracture toughness of the ZYTO system may be shortcomings compared with 7-8YSZ: the traditional TBC. In this study, ZYTO composite ceramics were successfully prepared by chemical coprecipitation reaction, and the microstructure of resulting composites was studied as a function of the doping of M-YTaO4. Mechanical properties, including the density, porosity, hardness and Young’s modulus, were all determinate; the toughening mechanism was verified by the crack growth behavior of the Vickers indentation test. The results suggest that M-YTaO4 refined the fluorite phase grain and strengthened the grain interface in the composite ceramic. The thermal mismatch between the second phase and matrix produced residual stress in the bulk and affected the crack propagation behavior. With the increase in M-YTaO4 doping, the grain coarsening and ferroelastic domains were observed in the experiments. The ferroelastic domains with orthogonal polarization directions near the crack tip evidenced the ferroelastic toughening mechanism. The competition among these crack behaviors, such as crack deflection, bridging and bifurcation, dominated the actual fracture toughness of the composite. The best toughening formula was determined in the two-phase region, and the highest indentation fracture toughness was about 42 J/m2, which was very close to 7-8YSZ’s 45 ± 5 J/m2.

Characterization of MoAlB ceramics synthesized via spark plasma sintering with Si addition and SiC reinforcement

The MoAlB phase with high purity and density from elemental precursors was successfully synthesized with SPS (Spark Plasma Sintering) at 1200 °C. Then, MoAlB-Si solid solution and MoAlB-SiC (5% SiC by volume) composite were fabricated to improve the mechanical properties and oxidation behavior of the MoAlB further. XRD (X-Ray Diffraction), SEM (Scanning Electron Microscopy), and EDS (Energy Dispersive X-Ray Spectroscopy) investigated the composition and microstructure of the MoAlB ceramics. The hardness was measured by the Vickers indentation test, and fracture toughness was calculated by radial cracks formed during the indentation test. The hardness and fracture toughness of pure MoAlB was 10.30 GPa and 6.73 MPa.m1/2. With the Si solid solution, the hardness increased to 11.93 GPa, while the fracture toughness decreased to 5.49 MPa.m1/2. The highest hardness and fracture toughness were obtained in the MoAlB-SiC composite, 12.39 GPa, and 7.38 MPa.m1/2, respectively. The oxidation tests of the samples were characterized in the air at 1200 ℃ for 12 h. A dense and continuous oxide layer was formed in all samples after 12 h at 1200 °C. While both Si solid solution and SiC reinforcement increase the oxidation resistance, the best results were obtained in the MoAlB-Si-SiC composite. The effect of Si addition and SiC reinforcement on electrical and thermal conductivity was measured from room temperature to 1000 ⁰C. The electrical conductivity of all samples decreased exponentially with the increase in temperature. The electrical conductivity of pure MoAlB was 2.82 S⋅m−1 at room temperature and decreased with the Si addition (2.49 S⋅m−1) or SiC reinforcement (2.67 S⋅m−1). On the other hand, thermal conductivity tends to decrease between room temperature to 400 °C but showed an increasing trend above 400 °C. In conclusion, the mechanical properties and oxidation resistance of MoAlB ceramics were improved with Si addition and SiC reinforcement.

Crack healing behavior of 4H-SiC: Effect of dopants

We investigate the crack-healing mechanism of 4H silicon carbide (4H-SiC) and reveal the effect of dopants on the crack-healing behavior of 4H-SiC. Vickers indentation tests and thermal annealing are utilized to generate cracks and heal cracks in 4H-SiC, respectively. High-temperature thermal annealing in the air atmosphere is found to be capable of effectively healing indentation-induced cracks and releasing indentation-induced stress in undoped 4H-SiC by the formation and viscous flow of glass phase SiO2. Nitrogen (N) doping is found to assist the atomic diffusion of 4H-SiC. The crack healing of N-doped 4H-SiC is realized by the synergy of host solid diffusion and the padding of glassy SiO2. In contrast, vanadium (V) doping hinders the viscous flow of SiO2 and results in the incomplete healing of cracks in V-doped 4H-SiC. Although the generation of cracks lowers the bending strength of 4H-SiC, the healing of cracks by the padding of glassy SiO2 is found to effectively recover the bending strength of indented 4H-SiC samples. Our work opens a pathway to design thermal processing technologies to heal the cracks and enhance the mechanical properties of 4H-SiC wafers.

Improved adhesion of cathodic arc PVD AlCrSiN coating on ion-implanted WC-Co substrates

Ion implantation has been shown to improve adhesion strength of AlCrSiN coatings due to a synergic enhancement on fracture toughness and load bearing capability of the substrate that can potentially increase the in-service efficiency of coated cutting tools. In this work, AlCrSiN coatings deposited by PVD on WC-Co substrates implanted with Ti, Cr and N ion species have been processed. The mechanical properties and adhesion have been characterized by contact techniques and the residual stress of the coatings and substrates have been evaluated using FIB-DIC technique and Vickers indentation tests, respectively. An improvement of adhesion strength is obtained for treated substrates, especially for those implanted with titanium and chromium ions. This improvement is attributed to the introduction of residual stresses in the substrate, which increases its fracture toughness and enhances its load bearing capability.

Orientation Dependence of Plastic Deformation Behavior and Fracture Energy Absorption Mechanism around Vickers Indentation of Textured Ti&lt;sub&gt;3&lt;/sub&gt;SiC&lt;sub&gt;2&lt;/sub&gt; Sintered Body

In order to clarify plastic deformation behavior and mechanism of fracture energy absorption of Ti3SiC2, Vickers indentation tests were conducted for Ti3SiC2 sintered bodies with various textured orientations. Textured Ti3SiC2 sintered bodies were fabricated by slip casting in a strong magnetic field and spark plasma sintering (SPS), and their orientation distribution were analyzed by SEM/EBSD. It was found that for the textured Ti3SiC2, the plastic deformation behavior around Vickers indents such as an indent shape and a grain pile-up were strongly affected by basal slip and kink deformation. Furthermore, the fracture energy absorption mechanism around the indents also depended on the texture orientations. From our results, it is concluded that the most effective factor for suppressing the crack propagation was the grain pile-up, and the second one was crack deflections.

Fracture toughness and hardness of in-office, 3D-printed ceramic brackets.

Three-dimensional (3D) printing technology is a promising manufacturing technique for fabricating ceramic brackets. The aim of this research was to assess fundamental mechanical properties of in-office, 3D printed ceramic brackets. 3D-printed zirconia brackets, commercially available polycrystalline alumina ceramic brackets (Clarity, 3 M St. Paul, MN) and 3D-printed customized polycrystalline alumina ceramic ones (LightForce™, Burlington, Massachusetts) were included in this study. Seven 3D printed zirconia brackets and equal number of ceramic ones from each manufacturer underwent metallographic grinding and polishing followed by Vickers indentation testing. Hardness (HV) and fracture toughness (K1c) were estimated by measuring impression average diagonal length and crack length, respectively. After descriptive statistics calculation, group differences were analysed with 1 Way ANOVA and Holm Sidak post hoc multiple comparison test at significance level α= .05. Statistically significant differences were found among the materials tested with respect to hardness and fracture toughness. The 3D-printed zirconia proved to be less hard (1261 ± 39 vs 2000 ± 49 vs 1840 ± 38) but more resistant to crack propagation (K1c=6.62 ± 0.61 vs 5.30 ± 0.48 vs 4.44 ± 0.30 MPa m1/2 ) than the alumina brackets (Clarity and Light Force respectivelty). Significant differences were observed between the 3D printed and the commercially available polycrystalline alumina ceramic brackets but to a lesser extent. Under the limitations of this study, the 3D printed zirconia bracket tested is characterized by mechanical properties associated with advantageous orthodontic fixed appliances traits regarding clinically relevant parameters.

Role of graphene in enhancing indentation and scratch properties of soda lime silicate glass

In this work, the role of graphene on indentation and scratch properties of soda lime silicate (SLS) glass is investigated by nanoindentation and nanoscratch as well as Vickers indentation tests. The results show that compared with bare SLS glass, the nanohardness and reduced modulus of graphene coated on SLS (G/SLS) glass are higher, because G/SLS glass surface can accommodate more strain energy through elastic process. The nanoscratch resistance of G/SLS glass is increased by ∼30%-44%, since the monolayer graphene can effectively reduce the friction force and activation volume of SLS glass during the mechanochemical wear process in humid air. Furthermore, the subsurface damage of G/SLS glass upon nanoindentation and nanoscratch tests are reduced, and the Vickers hardness and indentation fracture toughness of G/SLS glass are increased. These results clearly show the monolayer graphene can protect the SLS glass surface from physical contact via both normal and tangential shear tests.

Improvement of scratch resistance in transparent hard surfaces through layer-by-layer coating

Layer-by-layer (LbL) coating can be a promising method to ameliorate the mechanical robustness of soft surfaces. To improve scratch resistance, we prepared composites in which a polymer and montmorillonite (MMT) were alternately deposited on hard-coating surfaces. The alternating deposition of each LbL layer was confirmed using the water contact angle and surface morphology, and the resulting LbL-coated hard surface had excellent optical transparency of over 95 % in the entire visible region. In addition, nanoindentation confirmed that the mechanical properties of the hard-coating surface were not considerably impaired even after the LbL coating. When the scratch creation characteristics were comparatively estimated using common mechanical analysis tools—such as nanoindentation, Vickers indentation, and dynamic-scratch tests—it was clearly noted that the MMT-coated surface exhibited superior scratch resistance, by >12 %, compared to other films in the dynamic-scratch test. Indentation methods only reflect the surface response to normal stress, but dynamic-scratch evaluations can identify the response to oblique-directional stress commonly working for scratch creation. Because planar MMTs reduce the actual friction against oblique stress, MMT-coated surfaces exhibit lower friction in dynamic-scratching test, ultimately providing improved scratch resistance.

Indentation creep behaviour of the magnesium AZ61–0.7Si–xBi cast alloys

Creep behaviour of the AZ61–0.7Si–xBi cast magnesium alloys were studied by Vickers indentation testing under constant load of 5 N in the temperature range of 423–523 K. The results indicate that increasing Bi content improved the creep resistance at all test temperatures. This was caused by the higher volume fraction of the thermally stable Mg3Bi2 intermetallic particles, as the principal strengthening cause, which compensated the possible effects of the lower amount of the Mg2Si particles. According to the obtained stress exponents of about 6.7 and activation energies in the range of 84.6–88.1 kJ mol−1, dislocation pipe diffusion was suggested as the dominant creep mechanism.

Experimental and first-principles study on TiB/TiC interface in hybrid (TiB+TiC)/Ti6Al4V composite

To understand the synergistic strengthening mechanism of hybrid TiB + TiC reinforcements in Ti matrix composites, the corresponding TiB/TiC interfacial characters and load-bearing capacity were revealed in this work through a coupled method of high-resolution transmission electron microscopy (HRTEM), ab-initio calculations, and Vickers indentation test. Results show the interfacial orientation relationship (OR) between TiB and TiC phases is [010]TiB//[11 2‾]TiC, (2 2‾ 0)TiC//(102)TiB, which exhibits an interface formation energy of 3.32 J/m2 estimated via first-principles calculations. The TiB/TiC interface shows a high adhesion strength of 5.78 J/m2 owing to the formation of strong B–C covalent bond, which is also slightly higher than the strength (5.52 J/m2) obtained within TiB. Moreover, the strong TiB/TiC interface contributes to the superior load-bearing capacity of the intergrowth ceramic structure with relatively higher hardness (∼2100 HV0.2) than that of individual TiB and TiC phases (around 2020–2030 HV0.2). Consequently, the hybrid TiB + TiC reinforcements exhibit a synergistic strengthening effect in Ti matrix composites due to the intergrowth microstructure characteristic with superior load-bearing capacity.

Effects of Aluminum Oxide Addition on Electrical and Mechanical Properties of 3 mol% Yttria-Stabilized Tetragonal Zirconia Electrolyte for IT-SOFCs.

Composite tetragonal zirconia (3Y-TZP) sinters with Al2O3 contents of 0, 1, 5, 10 and 15 mol% were obtained from a 3-YSZ powder prepared using the gelatin method, and the influence of alumina addition on the mechanical and electrical properties of the obtained sinters was investigated. Al2O3 was added via two different methods, namely during the preparation of the 3-YSZ powder and via impregnation using an alcohol solution of aluminum nitrate. The obtained green bodies were sintered for 2 h in air at 1773 K. The structure and morphology of the two series of sinters were investigated using XRD and SEM-EDS, their electrical properties were determined using impedance spectroscopy, and their hardness and critical stress intensity factor were measured using the Vickers indentation test. We established that both the amount of alumina and the method used to introduce it into the 3Y-TZP matrix significantly affect the physicochemical properties of the obtained polycrystalline material. The 3-YSZ/10 mol% Al2O3 sinter that had Al2O3 introduced during the preparation of the 3-YSZ powder was found to exhibit the most advantageous mechanical and electrical properties while still having sufficiently low porosity.

Surface, Chemical, and Tribological Characterization of an ASTM F-1537 Cobalt Alloy Modified through an Ns-Pulse Laser

Metallic biomaterials are considered safe materials for the fabrication of orthopedic prostheses due to their mechanical stability. Among this group, cobalt-chromium-molybdenum alloys are commonly used. Nevertheless, adverse reactions on tissues caused by the liberation of metallic ions are a limitation. Therefore, the modification of biometallic material surfaces has become a topic of interest, especially the improvement of the wear resistance to retard the degradation of the surface. In this work, dimples obtained at different processing parameters by an ns-pulse laser were texturized on an ASTM F-1537 cobalt alloy. Surfaces were characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy, and Raman spectroscopy. The mechanical integrity of the surface was evaluated using a 3D surface analyzer and Vickers indentation tests. The tribological response was studied employing a ball-on-disc tribometer under lubricated conditions tracking the coefficient of friction, volume loss, wear rate, and surface damage by SEM. The variation of the laser power, repetition rate, and process repetitions slightly modified the chemistry of the surface (oxides formation). In addition, the rugosity of the zone treated by the laser increased. The texturized samples decreased the wear rate of the surface in comparison with the untreated samples, which was related to the variation of the dimple diameter and dimple depth.

Microstructural Evolution as a Function of Increasing Aluminum Content in Novel Lightweight Cast Irons

In the context of the development of new lightweight materials, Al-alloyed cast irons have a great potential for reducing the weight of the different part of the vehicles in the transport industry. The correlation of the amount of Al and its effect in the microstructure of cast irons is not completely well established as it is affected by many factors such as chemical composition, cooling rate, etc. In this work, four novel lightweight cast irons were developed with different amounts of Al (from 0 wt. % to 15 wt. %). The alloys were manufactured by an easily scalable and affordable gravity casting process in an induction furnace, and casted in a resin-bonded sand mold. The microstructural evolution as a function of increasing Al content by different microstructural characterization techniques was studied. The hardness of the cast irons was measured by the Vickers indentation test and correlated with the previously characterized microstructures. In general, the microstructural evolution shows that the perlite content decrease with the increment of wt. % of Al. The opposite occurs with the ferrite content. In the case of graphite, a slight increment occurs with 2 wt. % of Al, but a great decrease occurs until 15 wt. % of Al. The addition of Al promotes the stabilization of ferrite in the studied alloys. The hardness obtained varied from 235 HV and 363 HV in function of the Al content. The addition of Al increases the hardness of the studied cast irons, but not gradually. The alloy with the highest hardness is the alloy containing 7 wt. % Al, which is correlated with the formation of kappa-carbides and finer perlite.