Ultrasonic Nanocrystal Surface Modification Research Articles

Low-cycle fatigue behavior and surface treatment of a twinning-induced plasticity high-entropy alloy

The low-cycle fatigue life and cyclic deformation behavior of a metastable high-entropy alloy were investigated in this study. Additionally, the effects of the ultrasonic nanocrystal surface modification (UNSM) process on tensile properties and fatigue life were evaluated. Heat treatment following the cold rolling of Fe40Mn40Co10Cr10 alloy plates resulted in the formation of a coarse grain size of 46.7 ± 19.6 μm. Additional mechanical twins were activated during tensile testing compared to the equiatomic CoCrFeMnNi alloy, leading to increased elongation. However, mechanical twins in cyclic loads appear only at high strain amplitudes. Therefore, similar to the CoCrFeMnNi alloy, the slip of dislocations was the dominant cyclic deformation mechanism and the fatigue life of the alloys were comparable. The UNSM process formed a deformed gradient layer with a thickness of approximately 200 μm on the alloy surface. In addition to mechanical twins and low-angle grain boundaries, ultrafine grains with diameters as small as 200 ± 120 nm are detectable in this layer. Although this surface treatment successfully increased the yield strength by more than 70%, fatigue crack initiation was accelerated and fatigue crack growth resistance was degraded.

Effect of surface engineering on wear and fatigue behavior of thermally sprayed SiC coating

The objective of this study is to investigate the effect of surface engineering technologies, namely, TSC (thermal spray ceramic) coating and UNSM (ultrasonic nanocrystal surface modification) technology on the wear and fatigue behavior of SiC coating. The effects of UNSM technology on microstructure, mechanical, wear, and fatigue properties were investigated. The UNSM-treated coating decreased the CoF (coefficient of friction) under both dry and non-dry conditions. The wear track morphology showed that the coating experienced abrasive wear in dry conditions. In contrast, in non-dry conditions, adhesive wear was a dominant mode. Moreover, the UNSM technology could extend the RBF (rotary bending fatigue) life of the as-sprayed SiC coating throughout the applied stress levels. It is expected that aerospace, nuclear, etc. industries may be benefited from the features of UNSM technology, such as an increase in hardness, residual stress, wear resistance, and fatigue properties of SiC coating.

VHCF, Tribology Characteristics and UNSM Effects of Bainite and Martensite Spring Steels

It has been reported that the duplex bainite microstructure obtained by austempering (AT) shows higher strength, ductility and impact toughness than quench and tempered (QT) martensite structure in SAE9254 spring steel. However, there seems to be no research on the very high cycle fatigue (VHCF) and tribology characteristics of bainite structure for durability design of next generation spring steel from the perspective of engineering and industrial applications. This is a follow-up study that quantitatively analyzed the mechanical properties, microstructural deformation characteristics, and impact toughness of bainite and martensite using EBSD (Electron Backscatter Diffraction) and SEM (Scanning Electron Microscope) analyses. In this study, VHCF, HCF, tribology characteristics and UNSM (ultrasonic nanocrystal surface modification) effects under duplex bainite and single martensite microstructures were quantitatively studied and analyzed by fracture mechanics from the engineering and industrial point of view to improve durability and weight reduction in spring steels. The bainite AT and martensite QT specimens showed a 56% and 33% increase in fatigue limit for as received AR specimens. Fisheye cracks in duplex bainite AT specimens are similar to ‘facet internal cracks’ that initiated in the absence of inclusions. Generally fisheye crack fracture mode is preferred in VHCF, but fisheye crack was not found in the QT and the AR specimens at all. The UNSM-treated specimens showed fatigue limits that were about 33~50% higher than the untreated specimens.

Revealing the deformation mechanisms of the heterogeneous structured CrMnFeCoNi high entropy alloy with ameliorated mechanical and corrosion resistance properties

Developing high entropy alloy (HEA) with both high strength and ductility is a longstanding challenge as potential structural materials. The strength and ductility trade-off can achieve via tailoring heterogeneous structures. Herein, a gradient structure with grain size variation from surface to center was successfully introduced into the CrMnFeCoNi HEA by ultrasonic nanocrystal surface modification (UNSM) process. More importantly, the deformation mechanisms and strengthening mechanisms of the heterogeneous structured CrMnFeCoNi HEA during tension were also investigated. Experimental results demonstrated that the heterogeneous structured CrMnFeCoNi HEA shows excellent strength and ductility combination properties ascribed to the grain refinement strengthening, dislocation density strengthening, and twinning strengthening. Besides, the corrosion resistance properties are also simultaneously improved, resulting from the low surface roughness, small grain size, and large compressive residual stress value. During tensile deformation process, the deformation mode is the dislocation slip at low strain and the slip system of the alloy is mainly {111}〈110〉. With the increase of deformation amount, twin crossing occurs, and grain size gradually decreases. The deformation mode changes from dislocation slip to twinning at high strain. In conclusion, the UNSM process ameliorates the comprehensive mechanical and corrosion resistance properties of CrMnFeCoNi HEA.

Ultrasonic Nanocrystal Surface Modification: Processes, Characterization, Properties, and Applications.

Ultrasonic nanocrystal surface modification (UNSM) is a unique, mechanical, impact-based surface severe plastic deformation (S2PD) method. This newly developed technique finds diverse applications in the aerospace, automotive, nuclear, biomedical, and chemical industries. The severe plastic deformation (SPD) during UNSM can generate gradient nanostructured surface (GNS) layers with remarkable mechanical properties. This review paper elucidates the current state-of-the-art UNSM technique on a broad range of engineering materials. This review also summarizes the effect of UNSM on different mechanical properties, such as fatigue, wear, and corrosion resistance. Furthermore, the effect of USNM on microstructure development and grain refinement is discussed. Finally, this study explores the applications of the UNSM process.

A Comparative Study on Mechanical and Corrosion Behaviours of α/(α + β) Mg-Li Alloys Subjected to Ultrasonic Nanocrystal Surface Modification

Ultrasonic nanocrystal surface modification (UNSM) was applied to hot-rolled Mg-Li alloys (LAE361 and LA106). The microstructure, mechanical properties, deformation mechanisms, and corrosion resistance properties of these alloys after UNSM treatment were systematically studied. Significant improvement in surface hardness and decrease in surface roughness were achieved by UNSM treatment. Meanwhile, the basal texture intensity of the Mg-Li alloys reduced significantly, and several deformation twins appeared on the surface layer. The α phase of the surface layer underwent twin deformation and basal plane slip. The fibre textures in the β phase of LA106 Mg-Li alloy changed from γ and η to α and ε, which mainly resulted in the dislocation slip. More importantly, UNSM treatment exhibited enhanced strength and improved plasticity of LAE361 and LA106 Mg-Li alloys. The corrosion current density of LAE361 Mg-Li alloy reduced approximately 29.3% by UNSM treatment, while it increased the corrosion current density of LA106 Mg-Li alloy by 189.7%. These studies show that the application of UNSM to improve the corrosion resistance of duplex phases of LA106 Mg-Li alloy needs further investigation.

Comparison of SP, SMAT, SMRT, LSP, and UNSM Based on Treatment Effects on the Fatigue Properties of Metals in the HCF and VHCF Regimes

This paper aims to provide a better understanding regarding the effects of shot peening (SP), surface mechanical attrition treatment (SMAT), laser shock peening (LSP), surface mechanical rolling treatment (SMRT), and ultrasonic nanocrystal surface modification (UNSM) on the fatigue properties of metals in high-cycle fatigue (HCF) and very-high-cycle fatigue (VHCF) regimes. The work in this paper finds that SMRT and UNSM generally improve the high-cycle and very-high-cycle fatigue properties of metals, while SP, SMAT, and LSP can have mixed effects. The differences are discussed and analyzed with respect to the aspects of surface finish, microstructure and microhardness, and residual stress. SMRT and UNSM generally produce a smooth surface finish, while SP and SMAT tend to worsen the surface finish on metals, which is harmful to their fatigue properties. In addition to inducing a plastic deformation zone and increasing microhardness, surface treatments can also generate a nanograin layer and gradient microstructure to enhance the fatigue properties of metals. The distribution of treatment-induced residual stress and residual stress relaxation can cause mixed effects on the fatigue properties of metals. Furthermore, increasing residual stress through SP and SMAT can cause further deterioration of the surface finish, which is detrimental to the fatigue properties of metals.

Multiphysics modeling of in situ integration of directed energy deposition with ultrasonic nanocrystal surface modification

Multiphysics modeling of in situ integration of directed energy deposition with ultrasonic nanocrystal surface modification

Effect of Ultrasonic Nanocrystal Surface Modification Treatment at Room and High Temperatures on the High-Frequency Fatigue Behavior of Inconel 718 Fabricated by Laser Metal Deposition

In this work, the effect of ultrasonic nanocrystal surface modification (UNSM) treatment at room and high temperatures (RT and HT) on the high-frequency fatigue behavior of Inconel 718 alloy fabricated by laser metal deposition (LMD) process was experimentally investigated. UNSM treatment at RT and HT modified a surface morphology and produced a nanostructured surface layer with a thickness of approximately 120 and 140 µm, respectively. The surface roughness of the untreated sample was reduced, while the surface hardness was notably increased after the UNSM treatment at RT and HT. Both increased with increasing the UNSM treatment temperature. Fatigue behavior of the untreated samples at various stress levels was slightly improved after the UNSM treatment at RT and HT. This is mainly due to the formation of a fine grained nanostructured surface layer with reduced porosity and highly induced compressive residual stress. Fatigue mechanisms of the samples were comprehensively discussed based on the quantitative SEM fractographic analysis.

Effects of surface modification on fuel-lubricated tribological behavior of WC-Co thermal spray coating

The objective of this study is to evaluate the effects of ultrasonic nanocrystal surface modification (UNSM) on the tribological behavior of WC-Co thermal spray coatings for fuel-lubricated components. UNSM reduced the average surface roughness from 4.22 µm down to 2.26 µm and increased the hardness from 861 HV1 up to 1091 HV1. UNSM reduced the intensity and broadened the full width at half maximum of X-ray diffraction peaks, which indicated a combination of refinement in grain size and introduction of compressive residual stress. The coefficient of friction under fuel lubrication was reduced significantly by UNSM from 0.083 to 0.011, while the specific wear rate decreased from 6.21 ± 1.41 × 10−13 mm3/N × m to 2.07 ± 0.36 × 10−13 mm3/N × m after UNSM.

Application of crosswise repetitive ultrasonic nanocrystal surface modification treatment to Inconel 690 alloy: Efficiency of single-path and multi-paths

In this study, the efficiency of crosswise repetitive ultrasonic nanocrystal surface modification (CR-UNSM) treatment on surface characteristics, tribological and fatigue properties of single and multi (double, triple, quadruple and quintuple) treated Inconel 690 alloy was investigated. All the CR-UNSM-treated specimens demonstrated better tribological and fatigue performance in comparison with the untreated specimen. Quintuple CR-UNSM-treated specimen demonstrated the lowest coefficient of friction (COF) and specific wear rate (SWR) among untreated and other CR-UNSM-treated specimens, while triple CR-UNSM-treated specimen was found to be the most effective in terms of fatigue performance. The surface roughness of Inconel 690 alloy was significantly reduced after single CR-UNSM treatment, afterwards it was gradually roughened with increasing the number of CR-UNSM treatment. The surface hardness along with hardened surface layer and also compressive residual stress (CRS) were increased with increasing the number of CR-UNSM treatment. Every CR-UNSM treatment was capable of refining coarse grains into nano-scale grains, where the higher number of CR-UNSM treatment the thicker nanostructured surface layer (NSL) and the finer grain size.

Through-Thickness Microstructures and Yield Strength Enhancement for AZ31 Mg Sheets Treated by Ultrasonic Nanocrystal Surface Modification

An ultrasonic nanocrystal surface modification (UNSM) technique was applied to a 1-mm thick AZ31 magnesium sheet. UNSM is a relatively new surface modification technique in which a hard, hemispherical tip (2.38 mm in diameter) strikes the surface at an ultrasonic frequency to induce plastically deformed gradient microstructures and deep compressive residual stresses through the thickness. After the UNSM treatment, the through-thickness microstructures were thoroughly investigated using electron microscopy and electron backscatter diffraction analysis. The through-thickness microstructures revealed zones that were severely deformed (down to 200 µm from the surface) and twin-dominated (200~300 µm deep from the surface). The severely deformed zone consisted of shear banding, grain subdivision and reorientation, due to the strong plastic deformation, accompanied by the formation of {10<math xmlns="http://www.w3.org/1998/Math/MathML"><mover accent='true'><mn>1</mn><mo>−</mo></mover></math>2} tensile twins (despite compressive strikes by the hemispherical tip), {10<math xmlns="http://www.w3.org/1998/Math/MathML"><mover accent='true'><mn>1</mn><mo>−</mo></mover></math>1}-{10<math xmlns="http://www.w3.org/1998/Math/MathML"><mover accent='true'><mn>1</mn><mo>−</mo></mover></math>2} double twins and {10<math xmlns="http://www.w3.org/1998/Math/MathML"><mover accent='true'><mn>1</mn><mo>−</mo></mover></math>1} compression twins. The cause for tensile twinning was examined through a literature survey. In the twin-dominated zone, the twining activity prevailed as the slip activity gradually decayed through the thickness. The UNSM-induced hardness and microstructure enhancement was found to be effective down to about 300~400 μm deep from the surface. Finally, the source of the increase in yield strength after the UNSM treatment of the AZ31 sheet was analyzed, and focused on individual cases of microstructural enhancement in the severely deformed zone and the twin zone, and the compressive residual stress.

Improvement in tribological behavior of thermal spray Cr2O3 and Cr3C2-NiCr coatings by ultrasonic nanocrystal surface modification

Ultrasonic nanocrystal surface modification was applied to Cr2O3 and Cr3C2-NiCr coatings. The aim of this study is to evaluate the effect of UNSM on the tribological behavior of the coatings. X-ray diffraction patterns and transmission electron microscopy images of the UNSM-treated coatings demonstrated a grain size refinement, which tended to increase the hardness of the coatings. Fuel-lubricated tribological test results revealed that the UNSM reduced coefficient of friction and specific wear rate of the coatings.

Method of ultrasonic nano-crystal surface modification for improvement of surface characteristics of AISI D2 heat-treated with different tempering conditions

AISI D2, an alloy tool steel, has been widely used as a cold-work die steel because of its excellent wear resistance, toughness, and machinability. However, when it is used as a mold or tool under a high load, high hardness and wear resistance are required to improve its service life. This study aimed to apply ultrasonic nanocrystal surface modification (UNSM), a local surface hardening technology, to the surface of D2 steel. To maximize the surface improvement effect achievable through UNSM, it is important to select the optimal process conditions according to the characteristics of the base metal. Therefore, the effects of UNSM were compared for different initial hardness values of D2 in this study. To this end, the base metal was subjected to different heat treatment conditions to exhibit different hardness values (approximately 40, 45, 50, and 55 HRc). Changes in the surface of the base metal were observed according to the three main parameters of the UNSM process: the load, inter-pass interval, and feed rate. No significant changes in the surface roughness and hardness were caused by the feed rate. As the inter-pass interval of UNSM decreased and the static load increased, the surface roughness of the base metal increased. However, the specimen with low initial hardness (D2-H40), the roughness improvement decreased as the load increased. On the other hand, the surface hardness improvement increased as the inter-pass interval decreased and the load increased regardless of the initial hardness of the base metal. It also was found that the specimen with the highest initial hardness (D2-H55) exhibited the greatest hardness improvement rate of 9% and smallest hardened layer thickness of 220 μm. In addition, the largest compressive residual stress (− 1,130.6 MPa) was formed on the surface of D2-H55 after UNSM, which occurred because the base metal with high initial hardness had limited plastic flow due to fine grains and low ductility, causing thus the energy repeatedly delivered by UNSM to be concentrated in a limited area. Consequently, reducing the inter-pass interval is effective on improving the surface roughness and hardness regardless of the material hardness. However, the load must be applied at an appropriate level, depending on the material hardness. Therefore, when D2 is heat-treated and used according to the product requirements, it will be effective to consider the changes after UNSM treatment based on hardness after heat treatment that were derived in this study.

Effect of Ultrasonic Nanocrystal Surface Modification on Wear Properties of High-Carbon High-Chromium Steel

Effect of Ultrasonic Nanocrystal Surface Modification on Wear Properties of High-Carbon High-Chromium Steel

Biomedical Alloys and Physical Surface Modifications: A Mini-Review.

Biomedical alloys are essential parts of modern biomedical applications. However, they cannot satisfy the increasing requirements for large-scale production owing to the degradation of metals. Physical surface modification could be an effective way to enhance their biofunctionality. The main goal of this review is to emphasize the importance of the physical surface modification of biomedical alloys. In this review, we compare the properties of several common biomedical alloys, including stainless steel, Co–Cr, and Ti alloys. Then, we introduce the principle and applications of some popular physical surface modifications, such as thermal spraying, glow discharge plasma, ion implantation, ultrasonic nanocrystal surface modification, and physical vapor deposition. The importance of physical surface modifications in improving the biofunctionality of biomedical alloys is revealed. Future studies could focus on the development of novel coating materials and the integration of various approaches.

Effects of static load on microstructural and mechanical performance of AISI 1050 medium carbon steel subjected to ultrasonic nanocrystal surface modification

In this study, the effects of mild (M1, M2, M3), moderate (O1,O2), and severe (S1, S2, S3) static loads of ultrasonic nanocrystal surface modification (UNSM) on AISI 1050 steel were investigated. The layer affected by severe plastic deformation at moderate and severe static loadings became much thicker and the nanocrystalline layer became dominant around the surface region. The layer thickness influenced by the UNSM reached approximately 350 μm. UNSM had a positive effect on the surface roughness and morphology via reducing the Ra between 0,3 μm and 0,8 μm excluding the highest static loads. Oxidation formation was observed on the surface at severe static load conditions. The microhardness showed a significant improvement independently of static loads, and the hardness depth reached up to approximately 250 μm after the UNSM. Remarkable alteration in surface hardness was observed by increasing static load. Higher static loads ensured both deposition the compressive residual stress to the surface and propagation towards interior. The compressive stress of −700 MPa and a stress depth of over 1 mm were obtained by severe static loading. The processes implemented by moderate and severe static loads showed better performance over both low and high-cycle fatigue behavior.

Effects of ultrasonic nanocrystal surface modification on dry tribological and slurry erosion performance of non-reinforced and reinforced Ni-based microwave clads

The aim of this study is to find out whether ultrasonic nanocrystal surface modification (UNSM) is capable of having a considerable impact on dry tribological and slurry erosion performance of Ni-based microwave clads. The non-reinforced and Cr7C3 reinforced Ni-based clads were produced using a microwave cladding method. The application of UNSM treatment reduced the surface roughness of the clads. The UNSM-induced effective depth of 200–350 μm refines the grain structure that influences the hardness. Interestingly, the effectiveness of UNSM treatment was weakened for the non-reinforced clad in dry tribology, whereas similar results were obtained for the reinforced clad in slurry erosion testing. Wear and slurry erosion mechanisms were comprehensively discussed based on the worn-out surface characterizations.

Effect of ultrasonic nanocrystal surface modification temperature: Microstructural evolution, mechanical properties and tribological behavior of silicon carbide manufactured by additive manufacturing

This study deals with the improvement in mechanical and tribological properties of silicon carbide (SiC) manufactured by additive manufacturing (AM) through ultrasonic nanocrystal surface modification (UNSM) at 23 °C (room temperature - RT) and 900 °C (high temperature - HT). It was demonstrated that the UNSM treatment temperature had a great effect on the mechanical and tribological properties of the as-printed SiC. The R a and R z surface roughness values of the as-printed SiC sample were reduced from 10.5 μm down to 6.5 μm and from 47.0 μm down to 25.9 μm after UNSM treatment at RT, respectively. Furthermore, it was further reduced down to 5.5 μm and 21.2 μm with increasing the UNSM treatment temperature. UNSM treatment at RT and HT was able to increase the surface hardness of the as-printed SiC sample from 2100 HV up to 2500 HV and 2700 HV, respectively. The coefficient of friction (COF) of the as-printed SiC sample was approximately 0.187, which reduced down to 0.172 and 0.141 after UNSM treatment at RT and HT, respectively. The specific wear rate (SWR) of the as-printed sample was 2.61 × 10 −12 mm 3 /N × m, and decreased to 1.58 × 10 −12 mm 3 /N × m and 6.46 × 10 −13 mm 3 /N × m after UNSM treatment at RT and HT, respectively. The results of this investigation help improve the performance of AM-based SiC that is the potential candidate for many high-temperature applications such as nuclear, aerospace, optical, etc. instead of SiC manufactured by sintering method. • The SiC-Si samples were manufactured by additive manufacturing method. • UNSM was applied to SiC-Si at RT and HT. • UNSM temperature increase resulted in finer grains and more deformation twins. • Ratio of SiC vs. Si changed after UNSM treatment at RT and HT. • The tribological properties of SiC-Si improved by UNSM at RT and HT.

Microstructural evolution and mechanical properties of Cu-based alloy by post-sintering ultrasonic nanocrystal surface modification

In this study, an ultrasonic nanocrystal surface modification (UNSM) was used to enhance mechanical properties of CuSn10Pb10 alloy. Top surface coarse grains were refined into nano-grains (mean size of 45–74 nm) after UNSM. Mechanical testing results revealed that the surface hardness, yield strength and ultimate tensile strength increased after UNSM owing to the formation of nano-grains containing some nano-twins that can be elucidated according to the Hall-Petch relationship. Grain size refinement mechanism was attributed to the increase in dislocation density and the formation of new dislocations, where the accumulation of them at low-angle grain boundaries caused a variation of the grain orientation.