Increase In Microhardness Research Articles

Influence of Cu and Co addition on metallurgical and wear characteristics of AlCrFeNi high entropy alloy

The creation of new alloys with improved qualities has become essential in modern industries for high-performance materials. This work’s main objective is to use vacuum arc melting (VAM) to synthesize two different high-entropy alloys (HEAs): AlCrFeNiCu and AlCrFeNiCo. The mechanical properties, phase composition, grain boundaries, and alloy composition of the HEAs were studied. The predominant crystal structure, the Body-Centred Cubic (BCC) phase was obtained for both alloys. Significantly, the Co-containing HEA showed a smaller particle size than the Cu-containing HEA, which led to a 14.21% increase in microhardness. It indicates that the Co-based HEA will likely perform better than the Cu-based HEA in applications prone to abrasion, and indentation, and requiring high hardness levels based on the observed microstructure and hardness parameters. According to wear surface morphology studies, main effects analysis and ANOVA show that increasing loads and sliding distances increase wear rate, whereas sliding velocity has less effect. The best wear rate-reducing parameters are 10 N, 0.5 m/s, and 500 m for Cu-containing HEAs, and the same can be predicted using regression analysis. The study categorizes the intricate worn surface structure by describing different surface properties and wear mechanisms, such as grooves, delamination, adhesive wear, and pitting.

TiC reinforced Ti6Al4V fabricated by circular oscillating laser directed energy deposition: Microstructure and wear resistance

Gaussian laser is a common laser source in the field of laser directed energy deposition (L-DED). However, Gaussian laser sources have certain limitations, as they produce elevated temperature differentials and internal stresses during L-DED, which can result in significant distortion and fracturing. To address these restrictions, this research proposes using a circular oscillating laser as the energy source for L-DED. TC4 deposition samples and 5 wt% TiC/TC4 composite deposition samples were prepared using both Gaussian laser directed energy deposition (GL-DED) and circular oscillating laser directed energy deposition (COL-DED), and the deposition samples prepared under the two laser modes were compared and studied. The results indicate that, in the process of COL-DED, the laser oscillates periodically at a constant frequency in the high-temperature molten pool, which produces a more consistent temperature gradient and improved stirring effect in the molten pool. This inhibits grain growth and effectively refines the grains. Compared to the TiC/TC4 deposition samples prepared with Gaussian laser, the average grain size of COL TiC/TC4 deposition samples decreased by approximately 54.3 %. Due to the effects of the high-power laser beam, TiC particles partially melted and decomposed into Ti and C. As the laser advanced, the molten pool cooled swiftly, ultimately precipitating uniformly distributed gray-white TiC hard phases. Compared to the TC4 alloy prepared with the Gaussian laser, the TiC/TC4 composite material manufactured with a circular oscillating laser exhibited a 24.5 % increase in microhardness (430.76 HV0.2) and a reduction in wear rate of approximately 42.15 % (to 1.4 × 10−6 g/mm). Circular oscillating laser directed energy deposition can, to a certain extent, improve the hardness and wear resistance of materials compared to Gaussian laser directed energy deposition.

Heat treatments-induced wear resistance of Inconel 718 superalloy fabricated via Laser based Powder Bed Fusion

Laser based Powder Bed Fusion (LPBF) stands out among Additive Manufacturing (AM) techniques for its ability to fabricate intricate geometries with high precision. However, LPBF produced parts, particularly Inconel 718 (IN718) superalloys, demand further exploration in microstructural and mechanical properties aspect. This study explores the effect of heat treatments on LPBF fabricated Inconel 718. Three distinct heat treatments involving diverse solutionizing temperatures and ageing steps were applied to the LPBFed IN718 alloy. As-printed samples showed columnar dendritic microstructure. The heat treatments led to precipitation of strengthening γ′′ and γ′ phases. A substantial increase in microhardness was observed after heat treatments. Wear tests revealed as-printed specimens suffered higher wear loss (∼889 μm) and coefficient of friction (COF) (∼0.627) attributed to Laves phase and low hardness of the matrix. However, heat-treated specimens exhibited substantially lower wear loss (∼217 μm) and COF (∼0.342), with HT2 condition demonstrating superior wear resistance attributed to a homogeneous microstructure.

Microstructure and mechanical properties of thin-walled TA1 titanium pipes fabricated by high-frequency induction welding

High frequency induction welding (HFIW) was effectively employed for the high-speed fabrication of thin-walled TA1 titanium pipes (TWTPs) with a nominal wall thickness of ∼0.6 mm. The microstructure and mechanical properties of TWTPs manufactured under varying welding parameters were investigated. The weld zone (WZ) exhibits a waist shape measuring ∼622 μm in width, and the width of the heat-affected zone (HAZ) spans between 763 and 864 μm. Both the WZ and HAZ are composed of a mixture of coarse serrated α grains with fine acicular and twins, while the BM retains equiaxed grains. This unique microstructure was resulted from the thermal cycling during HFIW, contributing to a notable increase in microhardness within the WZ compared to both the HAZ and the BM. Optimal manufacturing conditions were identified at a welding power of 14.4 kW, a welding speed of 60 m/min, an opening angle of 6°, and a squeeze displacement of 0.2 mm, yielding the TWIP with a tensile strength of ∼307 MPa and tensile elongation of ∼27%. Tensile fracture analysis revealed that failure predominantly occurred within the BM, underlining a ductile fracture mode characterized by pronounced dimple formations. The enhanced mechanical performance of the weld joints can be attributed to the heterogenous microstructure in the WZ, where the presence of large serrated α-grains enhances ductility, and the fine martensite and twins contribute to the high strength.

Effects of Thermal Variables of Solidification on the Microstructure and Hardness of the Manganese Bronze Alloy Cu-24Zn-6Al-4Mn-3Fe

The Cu-24Zn-6Al-4Mn-3Fe alloy is mainly used for the manufacture of sliding bushings in the agricultural sector due to its high mechanical properties in the cast state. Understanding how the casting thermal parameters affect the microstructure and impact the properties of alloys is fundamental to optimizing manufacturing processes and improving performance during their application. In this study, the Cu-24Zn-6Al-4Mn-3Fe alloy was unidirectionally solidified under non-steady heat flow conditions using a water-cooled graphite base for heat exchange. Seven points were monitored along the longitudinal region of this ingot, and the data to obtain the solidification variables were extracted using an acquisition system. The cooling rates varied from 4.50 °C/s to 0.22 °C/s from the closest to the furthest position from the heat extraction point. The microstructure was analyzed via optical microscopy, scanning electron microscopy and X-ray diffraction in order to characterize the phases and intermetallic elements present in the material. The mechanical properties were evaluated through hardness and microhardness tests throughout longitudinal extension of the solidified part. The results showed an increase in hardness and microhardness with a decrease in the cooling rate, which may be related to the increase in size and the κ phase fraction with a decrease in the cooling rate, as analyzed via optical microscopy and scanning electron microscopy. Furthermore, in all positions, there was no significant change in the amount of the α phase retained, with the matrix being mainly composed of the β phase and a small content of approximately 2% of the α phase.

Impact of Boron Nitride(H) reinforcement on the properties of 5.8% copper-based aluminium alloy surface composite done by friction stir processing

ABSTRACT Numerous experiments and research is underway within the realm of aluminium metal matrix surface composites (MMSCs). This material has been applied in various marine, and aerospace industries, on account of its remarkable mechanical properties and desirable weight to strength ratio. The current study is focused on the synthesis of surface composites comprising of BN(H) reinforced 5.8% Cu aluminium alloy matrix composites. Boron Nitride(H) was reinforced on the surface of the Aluminum Alloy by FSP. Grooves were machined on the surface of the matriux and compacted with reinforcement particles. The wear rate, tensile behaviour, and microhardness were evaluated for the fabricated surface composites. The microstructural analysis was done via EDAX and FE-SEM to establish the presence of the reinforced particles. The tensile strength increased marginally with an increase in microhardness and reduction in elongation percenatge. The wear morphology aided in identifying the various wear mechanisms observed.

Achieving metallurgical bonding in steel faceplate/aluminum foam sandwich via hot pressing and foaming processes: interfacial microstructure evolution and tensile behavior

This study introduces an innovative approach to fabricating aluminum foam sandwich with aluminized steel faceplates through metallurgical bonding. The process involves the use of foamable precursor, prepared via melt stirring, and subsequent hot pressing and foaming, offering a cost-effective and industrially feasible method for producing lightweight structural materials and connection of steel/aluminum dissimilar metals. This study focuses on exploring the changes in the microstructure of the bonding interface before and after foaming, and revealing the impact of these changes on the tensile results. Foaming experiment shows that foamable sandwiches have superior foaming ability, and the core layer density after foaming is between 0.283 and 0.591 g/cm ³. Microstructural characterization results demonstrate that, during the hot pressing process, fine equiaxed grains are observed on the iron side of the interface, indicating dynamic recrystallization occurred. The formation of a small amount of η-Al5Fe2 at the interface is a primary factor causing the deflection of the fracture path. Subsequently, during the foaming process, intermetallic compounds (IMCs) θ-Al13Fe4, τ5-Al7Fe2Si, and β-Al4.5FeSi formed sequentially, mainly determined by the diffusion reaction of silicon elements. The formation of these IMCs led to an increase in microhardness at the interface and a decrease in shear strength. Digital image correlation was utilized to examine strain distribution under tensile loading. The result indicates that the damage accumulation is characterized by the formation and expansion of strain bands, with failure manifested as the interconnection of these strain bands.

Plasma electrolytic oxidation deposited HAp-Ta2O5 composite coatings on Ti6Al4V for biomedical applications: The importance of Ta2O5 reinforcing phase

In this research, the focus was placed on enhancing the properties of hydroxyapatite (HAp) coating by the addition of various concentrations of tantalum pentoxide (Ta2O5) nanoparticles, ranging from 0 to 1.5 g/L, to its electrolyte solution. The HAp-Ta2O5 composite coatings were deposited on the Ti6Al4V metallic implant using the plasma electrolytic oxidation technique. The results of the X-ray diffraction test indicated that the increased concentration of Ta2O5 nanoparticles has no significant effect on the phase composition of the coatings. The denser and rougher coatings were fabricated when 1.5 g/L of Ta2O5 nanoparticles were added to the solution. The favorable microstructural properties of the HAp-1.5 g/L Ta2O5 composite coating resulted in a notable improvement in the mechanical properties, i.e., >40% increase in both microhardness and bonding strength compared to HAp. The corrosion resistance of the coated implants was evaluated through electrochemical impedance spectroscopy and potentiodynamic polarization tests. The inclusion of Ta2O5 nanoparticles in HAp coating led to a 72% reduction in the corrosion current density of HAp, indicating the constructive contribution of the nanoparticles to improved corrosion protection. The samples were incubated in simulated body fluid for 7 days to assess their in vitro immersion performance. All of the PEO-derived coatings stimulated the nucleation and growth of apatite grains, showing their superior biomineralization ability. An obvious decrease in the level of harmful ions such as Al3+ and V5+ released from the surface of composite coatings was obtained. These findings suggest that the developed system has potential for dental and orthopedic applications.

Evaluation of Micro Hardness of Magnesium Alloy Coated with ZnO and Al2O3

Magnesium and its alloys have wide range of application in automobile and aircraft industries because of their excellent mechanical properties i.e. high strength to weight ratio, availability and good castability etc. However, some challenges occur in using magnesium in aquas service applications, due to its highly reactive nature and low tribological properties such as low wear and corrosion resistance. In this work an experimental study has been done on uncoated and ceramic coated AZ91 alloy to compare hardness and wear properties of both. The coating was applied on varying weight percentage of ZnO and Al2O3ceramic particles. The effect of presence of ceramic particles on the surface of substrate was studied using scanning electron microscope. Micro Vickers hardness test and wear tests were conducted on the samples, and it was found that coating of ceramic particles made the surface harder and wear resistant as compared to the uncoated Mg alloy. Contribution of Al2O3 particles plays an importantrole in increasing the hardness and wear resistance of coated surface. A decrease of 84% in coefficient of friction, increase in wear resistance by 99% and increase in micro hardness by 92% was reported for Al2O3 coated sample as compared to the uncoated surface.

The manufacture, optical properties, and mechanical aspects of europium-doped borate glasses

An investigation into the optical and mechanical properties of a novel borate glasses with the chemical composition of 70 B2O3-10 Li2O-10ZnO-5Bi2O3-5CaO-xEu2O3 was conducted. The glassy specimens of Eu3+-doped borate were prepared by the melting-quenching technique. An enhanced density from 3.0860 to 3.2176 g cm−3 and reduced molar volume from 29.27819 to 29.17447 (cm3 mol−1) are the outcome of increasing the concentration of Eu3+ in glasses. Plotting the extinction coefficient, dielectric constant (ε1, ε2), and refractive index (n) against wavelength reveals that they all rise as level of Eu3+ elements in the glass lattice increases. An increase in Eu3+ concentration results in a decrease in both the volume (VELF) and surface (SELF) energy loss functions. Also, all elastic-mechanical moduli (such as Young’s, Bulk, Shear, and Elongation) increase with increasing the quantity of Eu3+ ions in the glass lattice. The Young’s modulus (Y, GPa) of the glassy specimens was 34.512, 36.089, 36.504, 36.730 and 37.114 GPa for x equal 0, 0.25, 0.5, 0.75 and 1 mol ratio in the glass system, and coded by Eu-0.0, Eu-0.25, Eu-0.5, Eu-0.75 and Eu-1.0, respectively. Growing Eu2O3 levels resulted in an increase in Micro-Hardness from 2.050 to 2.146 GPa. Poisson’s ratio values for Eu-0.0, Eu-0.250, Eu-0.5, Eu-0.75 and Eu-1.0 were 0.273, 0.275, 0.277, 0.277 and 0.278, respectively.

Tribological, mechanical and microstructure characteristics of hybrid aluminium matrix composite containing titanium carbide (TiC) and graphite particles

The present study emphasize on the characterization and microstructure evaluation of aluminium composite with different weight fraction of constituents. These composites were produced by incorporating titanium carbide and graphite particles in the aluminium matrix through stir casting technique. The composites were characterized by evaluating the micro hardness, density, tensile strength, peak elongation and impact strength. Scanning electron microscopy and X-ray diffraction tests were performed to investigate uniform dispersion of the reinforcement particles in the matrix. It is evident that the addition of reinforcement particles with aluminium matrix yielded an increase in micro hardness and density by 62.82% and 7.05% respectively when compared to matrix. Tensile tests exposed that there was improvement in ultimate strength from 170 to 239.11 MPa while the elongation was dropped to 7.1%. The microscopic study of the specimen explored the plastic deformation through existence of dimples, ridges in the wrecked surfaces.

Impact of precursor content on microstructure and properties of in-situ synthesized Ni60A-xTiC ceramic composite coating

To improve the surface properties of copper components, Ni60A-xTiC composite coatings with different precursor (TiFe and Cr3C2) contents were fabricated on copper surface by plasma cladding in this paper. The surface of all composite coatings forms a ceramic film composed of a dense layer (TiO2 and Ti2O3) and a loose layer (Fe2O3 and FeO). As the precursor content increases, the number and size of TiC particles in the composite coating have a tendency to increase, resulting in a gradual increase in microhardness. The wear resistance of the composite coating increases first and then decreases. Too high precursor content (20 wt. %) can lead to poor interface connection and wear resistance deterioration of the coating. Furthermore, the melting loss resistance of the composite coating is significantly better than that of the Ni60A coating due to the barrier effect of the ceramic film, and it becomes better with the increase of precursor content. To sum up, the composite coating with 15 wt. % precursor content is more suitable because of its smooth appearance, good interface connection and excellent comprehensive performance.

Physical, Structural and Elastic Properties of New Oxyfluoride Borate Glasses

New mixed alkali/alkaline oxyfluoride borate glasses with composition xCaF2–(50-x)LiF–50B2O3 (x = 0, 5, 10, 15 and 20 mol%) were prepared by the conventional melt-quenching technique. X-ray diffraction (XRD) patterns confirmed the amorphous nature of the prepared samples, while energy dispersive X-ray (EDX) analysis confirmed the presence of the constituent elements B, O, F, and Ca. Fourier transform infrared (FTIR) spectra revealed the formation of BO3, BO2F, BO4 and BOF3 structural groups, as well as non-bridging oxygen/fluorine atoms in the glass network. The concentrations of these structural groups were found to vary with CaF2 concentration. The measured density and the calculated molar volume were found to increase over the entire range of composition. The increase in ultrasonic velocity, elastic moduli, micro-hardness and Debye temperature with the addition of CaF2 was discussed in terms of competition between the above-mentioned borate groups. Fraction of four-coordinated boron atoms, average boron–boron separation, fluorine molar volume, total packing density, dissociation energy per unit volume and average cross-link density were estimated. A close correlation is achieved between these quantities and elastic properties. Excellent agreement is found between the experimentally determined values and the theoretically calculated values of elastic properties from Makishima–Mackenzie's theory.

Assessment of surface microhardness of enamel surface treated with Nano- HAP serum before and after bleaching

Background: Although bleaching is typically considered a safe procedure, various investigations have found minor negative effects and changes in mineral composition. The aim was to Evaluate and compare the efficacy of using Nanohydroxyapatite serum on surface microhardness of enamel surface before and after bleaching with chemically cured Boost bleaching. Material and methods: ten sound human permanent upper and lower premolar teeth were used and their roots were removed 2 mm apically to the cementoenamel junction, the crowns were sectioned mesiodistally into two halves buccal and lingual/palatal, the buccal surface was further subdivided into two halves. The samples were embeded in an acrylic resin, resulting in 30 specimens divided into 3 groups: Control group: using Boost bleaching and stored in artificial saliva for 14 days, prevention group: nanohydroxyaptite (n-HAP) serum applied 2-3 min once daily for 10 days followed by bleaching then stored for 14 days in artificial saliva and treatment group: in which bleaching used before nanohydroxyapatite serum and stored in artificial saliva for 14 days. The samples were subjected to a Vickers microhardness test measured at 4 times: base line, after nanohydroxyapatitem, after one day of bleaching and after storage in artificial saliva for 14 days in all groups. The data were analyzed statistically using repeated analysis of variance (ANOVA) test followed by Tukey's test. Results: there was a significant increase in microhardness in the prevention group (p<0.05) while there was no significant difference in microhardness readings in control and treatment groups (p> 0.05). Conclusion: n-HAP may enhance the microhardness of a bleached enamel surface when used as a preventive & treatment measure. Suggested that a higher increase in enamel microhardness occurs when n-HAP is used for 2-3 min once daily for 10 days before bleaching and maintaining this increase even after storage for 14 days in artificial saliva.

Comparison of remineralizing efficacy of two novel preparation of arginine and theobromine on white spot lesion - an in vitro SEM analysis

ABSTRACT Purpose Evaluation of the efficacy of two novel formulations of arginine and theobromine in remineralizing artificial enamel defects using in vitro testing techniques- Microhardness and SEM Materials and methods Enamel slabs measuring 3 mm by 3 mm by 1.5 mm were created using 11 healthy premolars that were excised for orthodontic treatment. Group 1 (control, treated with merely a remineralization solution), Group 2 (0.05% arginine in 10 ml distilled water), and Group 3 (2% theobromine in 10 ml distilled water) were the three groups to which the slabs were randomly allocated (n = 7 per group). The pH cycle was run for 14 days, starting with a 72-h demineralization period and ending with 11 days of remineralization in the corresponding solutions. Prior to and during remineralization, microhardness was measured, and surface features were assessed using scanning electron microscopy (SEM). Statistical analysis, including Paired T Test, one-way ANOVA, and post hoc Tukey tests, determined that the mean values were significant at the 0.05 level. Results The control group showed a mean microhardness increase from 192.09 ± 19.30 to 208.58 ± 5.76. The arginine group increased significantly from 217.20 ± 4.24 to 304.00 ± 15.96, and the theobromine group from 214.09 ± 7.67 to 283.14 ± 10.91. Statistical analysis indicated that both arginine and theobromine groups had significantly greater microhardness improvements compared to the control (p < 0.05). SEM revealed that although arginine and theobromine enhanced enamel microhardness, surface morphology remained irregular and non-uniform. Conclusion Arginine and theobromine improve enamel microhardness and promote remineralization, but they do not create a uniform surface texture. Further research is needed to optimize their use and explore long-term effects on enamel surface uniformity.

Study on shot peening strengthening 42CrMoA steel and its fretting wear properties

In order to improve the tribological properties of 42CrMoA steel, it was shot peened using different parameters. The surface morphology, residual stresses, hardness, and micromotor properties of the treated specimens were thoroughly evaluated. The results showed that it led to substantial plastic deformation, increased surface roughness, grain refinement, and introduction of residual compressive stresses. In addition, a significant increase in microhardness and depth of hardened layers on the specimen surfaces was observed. Furthermore, a positive correlation between the effect of the shot peening process and the peening duration was observed. As revealed by the investigation, the shot peening process not only advances the wear resistance of the specimens but also leads to a reduced wear volume compared to untreated specimens. Furthermore, this treatment triggers a shift in the wear mechanism from the predominant occurrence of severe adhesive wear, fatigue wear, and abrasive wear in untreated specimens to a predominant mode of abrasive wear, accompanied by a minor occurrence of adhesive wear.

Comparing the remineralization potential of undemineralized dentin powder versus chicken eggshell powder on artificially induced initial enamel carious lesions: an in-vitro investigation

BackgroundWhite spot lesions are a widespread undesirable effect, especially prevalent during fixed orthodontic treatments. The study compared the in vitro enamel remineralization potential of undemineralized dentin matrix (UDD) versus chicken eggshell powder (CESP) for artificially induced enamel lesions.Methods100 caries-free and sound maxillary premolars were randomly divided into four groups each contain 25 teeth: Group I (Baseline): No treatment was done to the enamel surface. Group II (Negative control ): The enamel surface of the teeth underwent demineralization using demineralizing solution to create artificial carious lesions then kept in artificial saliva. Group III (CESP treated): After demineralizing the tooth surface, the teeth have been suspended in the CESP remineralizing solution. Group IV (UDD treated): After enamel demineralization, the teeth were suspended in UDD remineralizing solution. The remineralization potential was assessed by Vickers microhardness testing, scanning electron microscopic examination (SEM), and energy dispersive X-ray (EDX).ResultsThe current study demonstrated an increase in the mean microhardness of CESP and UDD-treated groups; however, It was nearer to the baseline level in the UDD group. SEM imaging revealed greater enamel remineralization in the UDD group compared to the remaining groups. The UDD group disclosed complete coverage for the prismatic enamel compared to the CESP group, which revealed a partially remineralized enamel surface. Interestingly, the Ca/P ratio increased significantly in the CESP group compared to the negative control group. In contrast, a higher significant increase in the mean Ca/P ratios was recorded in the UDD group compared to the test groups.Conclusionbiomimetic UDD and CESP powder should be utilized to treat enamel early carious lesions. However, UDD demonstrated the most significant remineralization potential.

A comparative evaluation of human enamel remineralization ability of biomimetic nacre against casein phosphopeptide-amorphous calcium phosphate: An in vitro study.

This study aimed to assess and compare the efficacy of Nacre and casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) on the remineralization of enamel using surface microhardness analysis, scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) spectroscopy. Twenty human maxillary premolars extracted for orthodontic reasons were collected. Under cool water spray, the crowns were sectioned mesiodistally into buccal and palatal halves using a diamond disc. The samples were subsequently mounted in self-cure acrylic resin. The samples were then subjected to Vickers hardness testing and SEM-EDX for baseline. To simulate carious lesions, all of the samples were acid-etched with 37% phosphoric acid for 30 s in a specific area on the enamel samples and subjected to surface microhardness testing and SEM-EDX. The enamel samples were randomly assigned to Group 1: Nacre water-soluble matrix (WSM), Group 2: Nacre varnish, and Group 3: CPP-ACP for remineralization. After 21 days, remineralization assessment of the test samples was done using SMH analysis and SEM-EDX analysis. Data obtained were statistically analyzed using the one-way analysis of variance to reveal the significant differences between the groups. Tukey's test was used for post hoc comparisons. All three groups showed a significant increase in surface microhardness. All three groups showed a significant calcium and phosphorous ratio increase after remineralization. Among the three groups, the highest Ca:P ratio was seen in the Nacre WSM group (0.58) followed by the Nacre Varnish (0.57) and CPP-ACP group (0.57). SEM images of the Nacre surface revealed the presence of extensive interlocking. A layer of packed hydroxyapatite particles was formed on the surface of the nacre through surface reactions. All the groups in the present study showed some extent of remineralizing ability irrespective of the different materials and mechanisms of action. Nacre WSM showed a remarkable hardness spike close to natural enamel after demineralization.

Local and global mechanical properties of orbital friction stir welding on API X65 PSL2 steel / Inconel 625 clad pipes

Orbital friction stir welding (FSW) is a promising approach to joining clad pipes. In this work, the influence of individual process parameters on the material flow even as, mechanical properties in orbital friction stir welded clad pipes is investigated. Due to the local heterogeneous microstructures within the weld, joints were evaluated by optical and scanning electron microscopy (SEM), microhardness, and digital image correlation (DIC). A microhardness increase was observed, with a maximum of 380 HV0.5 within the Inconel 625 and 265 HV0.5 within the X65 steel stir zones. Sound joints had an average ultimate tensile strength (UTS) exceeding up to 13% of the calculated theoretical tensile strength, which is obtained considering the minimum tensile strength of both materials. Additionally, failure occurred in the base material during the tensile testing, where the local strain in the stir zones of the X65 steel and Inconel 625 were only 3.3% and 10%, respectively. In summary, this investigation shows friction stir welded joints of API X65 steel and Inconel 625 clad pipes with high mechanical properties.

Effect of laser shock peening on tribological properties of 55SiMoVA bearing steel

Wear is an important factor limiting the service life of 55SiMoVA bearing steel. In this work, laser shock peening (LSP) technology is used to improve the tribological properties of 55SiMoVA bearing steel, and the corresponding underlying mechanism is systematically discussed. After LSP, the kurtosis (Sku) of surface roughness asperities reduced from 10.355 to 5.488, and no new phase was generated. Electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) analysis suggested LSP induced the generation of dislocation structures and deformation twins, leading to a decrease in the average grain size and an increase in the fraction of high-angle grain boundaries. Due to the work-hardening and fine-grain strengthening, the microhardness increased by 16.6 %, the maximum residual compressive stress amounted to −793.1 MPa, and the coefficient of friction (COF) and wear volume were significantly reduced. Scanning electron microscopy (SEM) results indicated that the wear mechanism of 55SiMoVA bearing steel before and after LSP was not transformed. However, the abrasive wear and delamination wear of the LSPed specimens were significantly improved, which was mainly attributed to grain refinement, increasing microhardness and constructing a residual compressive stress layer in the subsurface layer of 55SiMoVA bearing steel. During the sliding process, the increase in microhardness limits micro-plowing on the wear surface, and the residual compressive stress inhibits the crack formation and expansion, improving the wear resistance of 55SiMoVA bearing steel.