Ultrasonic Nanocrystal Surface Modification Treatment Research Articles

Effects of Pre- and Post-Carburizing Surface Modification on the Tribological and Adhesion Properties of Heat-Resistant KHR 45A Steel for Cracking Tubes.

In this study, the effects of ultrasonic nanocrystal surface modification (UNSM) technology on the tribological properties and scratch-induced adhesion behavior of a heat-resistant KHR 45A steel cracking tube, which is used for the pyrolysis process, were investigated. The main objective of this study is to investigate the effects of pre- and post-carburizing UNSM treatment on the tribological and adhesion performances of carburized domestic KHR 45A (A) steel and to compare the results with the existing carburized Kubota-made KHR 45A steel (B). A carburizing process was carried out on the polished and UNSM-treated KHR 45A steel substrates, which were cut out from the cracking tube, at 300 °C heat exposure for 300 h. The thickness of the carburizing layer was about 10 μm. UNSM technology was applied as pre- and post-carburizing surface treatment; both reduced the friction coefficient and wear rate compared to that of the carburized KHR 45A steel substrate. It was also found that the application of UNSM technology increased the critical load, which implies the improvement of adhesion behavior between the carburizing layer and the KHR steel substrate. The application of UNSM technology as pre- and post-carburizing surface treatment could help replace carburized Kubota-made KHR 45A steel (B) thanks to the improved tribological performance, enhanced scratch resistance, load bearing capacity, and adhesion of domestic KHR 45A (A) steel.

Improving plain and fretting fatigue resistance of A100 steel using ultrasonic nanocrystal surface modification

In this study, ultrasonic nanocrystal surface modification (UNSM) was used to improve plain and fretting fatigue properties of A100 steel. Results showed that an obvious plastic deformation layer was induced in A100 steel, and the martensite microstructure was remarkably refined. In addition, surface compressive residual stress after UNSM treatment was enhanced to 1700 MPa due to the severe lattice distortion. The increased surface hardness and the presence of beneficial compressive residual stresses after UNSM treatment significantly enhanced the plain/fretting fatigue resistance of A100 steel by retarding fatigue crack nucleation and propagation.

Effect of multiple ultrasonic nanocrystal surface modification on surface integrity and wear property of DZ2 axle steel

Ultrasonic nanocrystal surface modification (UNSM) treatments with different numbers of rolling passes are employed to enhance the surface integrity and the wear resistance of DZ2 axle steel for high-speed trains. In this study, microstructures, residual stress, and wear properties of the DZ2 axle steel after multiple UNSM treatments were investigated. The results showed grain refinements in the near-surface layer of the DZ2 axle steel after multiple UNSM treatments. Compared with the untreated sample, the compressive residual stress of the surface increased from −73 to −703 MPa, and the surface microhardness increased from 220 to 283 HV 0.2 . The results from wear tests showed that the sample with UNSM treatment of three rolling passes exhibited a significantly enhanced wear resistance under sliding conditions. • A nanostructured surface layer was fabricated on DZ2 axle steel through multiple UNSM processing. • Multiple UNSM treatment can introduce high compressive residual stress and hardness. • The surface-modified layer reduces the coefficient of friction. • The depth of deformed layer increases with increasing number of rolling pass.

Better Surface Integrity and Tribological Properties of Steel Sintered by Powder Metallurgy.

The current research reports the improvement in surface integrity and tribological characteristics of steel prepared using a powder metallurgy (PM) by ultrasonic nanocrystal surface modification (UNSM) at 25 and 300 °C. The surface integrity and tribological properties of three samples, namely, as-PM, UNSM-25 and UNSM-300 were investigated. The average surface roughness (Ra) of the as-PM, UNSM-25 and UNSM-300 samples was measured using a non-contact 3D scanner, where it was found to be 3.21, 1.14 and 0.74 µm, respectively. The top surface hardness was also measured in order to investigate the influence of UNSM treatment temperature on the hardness. The results revealed that the as-PM sample with a hardness of 109 HV was increased up to 165 and 237 HV, corresponding to a 32.1% and 57.2% after both the UNSM treatment at 25 and 300 °C, respectively. XRD analysis was also performed to confirm if any changes in chemistry and crystal size were took place after the UNSM treatment at 25 and 300 °C. In addition, dry tribological properties of the samples were investigated. The friction coefficient of the as-PM sample was 0.284, which was reduced up to 0.225 and 0.068 after UNSM treatment at 25 and 300 °C, respectively. The wear resistance was also enhanced by 33.2 and 52.9% after UNSM treatment at both 25 and 300 °C. Improvements in surface roughness, hardness and tribological properties was attributed to the elimination of big and deep porosities after UNSM treatment. Wear track of the samples and wear scar of the counter surface balls were investigated by SEM to reach a comprehensive discussion on wear mechanisms. Overall, it was confirmed that UNSM treatment at 25 and 300 °C had a beneficial effect on the surface integrity and tribological characteristics of sintered steel by the PM that is used in a shock absorber for a car engine.

Artificial neural network-based prediction model of residual stress and hardness of nickel-based alloys for UNSM parameters optimization

Ultrasonic Nanocrystal Surface Modification (UNSM) is known as one of the surface treatment techniques that utilizes an ultrasonic vibration energy to improve mechanical properties and performance of materials. The dynamic nature of this surface treatment process deforms the top surface and subsurface of materials with a very high strain rate, which makes the direct observation of residual stress and refined layers very difficult. In this study, a novel alternative approach is proposed that is based on the artificial neural network (ANN) concept for predicting residual stress and hardness of various nickel-based alloys that have been subjected to UNSM treatment. Experimental measurement data were used in the ANN training process and validation. The trained model showed the capability of predicting residual stress and hardness accurately with a Pearson correlation value (R) of 0.988 and 0.996, a root mean squared error (RMSE) of 84.231 and 17.028, and a mean absolute error (MAE) of 68.586 and 13.450 for residual stress and hardness models when tested using the test dataset, respectively. It can be concluded that ANN as the alternative approach is a suitable method for accurately performing prediction for practical use in the absence of a mathematical model. Since the experimental result was used in the ANN model training process, the predicted result by the ANN model appears to agree with the experimental results of the UNSM treatment. Because of these demonstration results, the ANN-based prediction model can be used as a tool to optimize the UNSM treatment parameters.

Effects of Surface Severe Plastic Deformation on the Mechanical Behavior of 304 Stainless Steel

In this study, two innovative surface severe plastic deformation (SSPD) methods, namely abrasive waterjet peening (AWJP) and ultrasonic nanocrystal surface modification (UNSM), were applied to a 304 stainless steel to improve the mechanical behavior. The surface roughness, microstructure, residual stress, hardness, and tensile mechanical properties of the alloy after the two SSPD treatments were studied systematically. The results show that both the AWJP and UNSM treatments have greatly positive effects on the mechanical-properties improvements by successfully introducing a hardening layer. Especially the UNSM-processed specimen possesses the most outstanding comprehensive mechanical properties (high strength with the comparable ductility). The yield strength with the UNSM treatment is 443 MPa, corresponding to the 109% and 19% improvements, as compared to that of the base (212 MPa) and AWJP-treated specimens (372 MPa). The results can be attributed to a much thicker hardening layer (about 500 μm) and a better surface integrity with lower roughness (Ra: 0.10 μm) formed by the UNSM technique.

A new guide for improving mechanical properties of non-equiatomic FeCoCrMnNi medium- and high-entropy alloys with ultrasonic nanocrystal surface modification process

Ultrasonic nanocrystal surface modification (UNSM) treatment on non-equiatomic medium- and high-entropy alloy (HEA) of Fex(CoCrMnNi)100-x is firstly introduced and its impact on microstructure and mechanical properties are revealed. By UNSM, severe plastic deformation-induced dislocation and deformation twins (DTs) arise at the topmost surface. Especially, Fe60(CoCrMnNi)40 (Fe60), which is classified as a medium-entropy alloy (MEA), exhibits ε-martensitic transformation. In the room temperature tensile test, a high strength of ∼600 MPa and ductility of ∼65 % elongation (strain to failure) is accomplished in Fe60. Initially formed DTs and ε-martensitic transformation by UNSM treatment plays a key role in retardation of necking point via both twinning-induced plasticity and transformation-induced plasticity. However, Fe20(CoCrMnNi)80 (Fe20) comparatively shows low strength of ∼550 MPa and ∼40 % elongation, owing to the low accommodation of DTs than Fe60. Our research will provide new guidelines for enhancing the mechanical properties of MEA and HEA.

Microstructure and mechanical properties of CoCrFeMnNi high entropy alloy with ultrasonic nanocrystal surface modification process

In this study, mechanical properties improvement of equiatomic CoCrFeMnNi treated with an ultrasonic nanocrystal surface modification (UNSM) was studied. The applied UNSM treatment with static loads of 10 N, 20 N, and 60 N provided a severe plastic deformation, which produced a gradient structure. The near-surface area exhibited a high number of dislocation densities and deformation twin interaction, leading to a surface strengthening and hardness improvement of up to 112% than the deformation-free interior region. Increment of dislocation densities and deformation twin formation on the surface also enhanced the yield and ultimate tensile strength of the UNSM-treated specimens. Furthermore, the combination of hard nanocrystallites layer on the surface and ductile coarse grain in the specimen interior as a result of the UNSM treatment successfully maintained the strength–ductility balance of the CoCrFeMnNi.

Mechanical and Tribological Characteristics of Cladded AISI 1045 Carbon Steel.

This study introduces a newly developed cladding device, through printing AISI 1045 carbon steel as single and double layers onto American Society for Testing and Materials (ASTM) H13 tool steel plate. In this study, the mechanical and tribological characteristics of single and double layers were experimentally investigated. Both layers were polished first and then subjected to ultrasonic nanocrystal surface modification (UNSM) treatment to improve the mechanical and tribological characteristics. Surface roughness, surface hardness and depth profile measurements, and X-ray diffraction (XRD) analysis of the polished and UNSM-treated layers were carried out. After tribological tests, the wear tracks of both layers were characterized by scanning electron microscopy (SEM) along with energy-dispersive X-ray spectroscopy (EDX). The surface roughness (Ra and Rz) of the single and double UNSM-treated layers was reduced 74.6% and 85.9% compared to those of both the as-received layers, respectively. In addition, the surface hardness of the single and double layers was dramatically increased, by approximately 23.6% and 23.4% after UNSM treatment, respectively. There was no significant reduction in friction coefficient of both the UNSM-treated layers, but the wear resistance of the single and double UNSM-treated layers was enhanced by approximately 9.4% and 19.3% compared to the single and double polished layers, respectively. It can be concluded that UNSM treatment was capable of improving the mechanical and tribological characteristics of both layers. The newly developed cladding device can be used as an alternative additive manufacturing (AM) method, but efforts and upgrades need to progress in order to increase the productivity of the device and also improve the quality of the layers.

Application of ultrasonic nanocrystal surface modification for improving surface profile of DEDed AISI 316L

This study investigated the effect of ultrasonic nanocrystal surface modification (UNSM) on the deteriorated surface of AISI 316L deposited using the direct energy deposition (DED) technology. After UNSM treatment, the coarse DEDed surface was fined, and a regular micro-surface profile was implemented. Compared to the case before UNSM treatment, the waviness and roughness of the surface after UNSM treatment decreased by up to 73.8 % and 86.2 %, respectively, and reduced further as the UNSM interval was decreased. Surface severe plastic deformation (S2PD) was induced in the dendrite structure of the UNSM-treated DEDed sample surface. The microstructure was deformed till a depth of up to 92.13 mm from the surface and was significantly affected by the interval. After UNSM treatment, the hardness improved by up to 71.5 % and gradually decreased from the surface to the inside; the hardness was improved by UNSM up to a maximum depth of 400 μm. Although the UNSM interval condition had a significant effect on the DEDed surface, it barely affected the relationship between the directions of DED deposition and UNSM treatment. This study confirmed that the UNSM technology can effectively improve a DEDed surface.

Ultrasonic nanocrystal surface modification of high-speed tool steel (AISI M4) layered via direct energy deposition

Abstract Tensile residual stress in the laser-deposited M4 fabricated by direct energy deposition (DED) may reduce the fatigue performance and tool life. Ultrasonic nanocrystal surface modification (UNSM) can induce compressive residual stress by generating severe plastic deformation of the material surface, and improve the wear resistance through surface texture refinement. In the present study, we investigated the changes in the metallurgical and mechanical properties of DEDed M4 specimens as induced by UNSM treatment. An X-ray diffraction analysis showed that the DEDed M4 austenite was transformed into martensite after UNSM processing. The change in the full width at half maximum revealed a grain size decrease of 25.8%. Conversion of the tensile residual stress within the DEDed M4 to compressive residual stress through UNSM treatment was confirmed. These changes in the metallurgical characteristics yield a 24.1% increase in the DEDed M4 hardness. A wear test was conducted to evaluate the wear resistances of heat-treated D2, DEDed M4 on D2, and UNSM-DEDed specimens. Ball-on-disk wear tests revealed that the DEDed M4 specimen wear rate was 68.3% lower than that of the H-D2. In addition, the DEDed M4 wear rate was reduced by 85.7% through UNSM treatment. The surface roughness was reduced by up to 88.3%, while micro-dimple shapes were formed on the DED-treated M4 surface. This study has demonstrated that UNSM can be applied to a DED-treated M4 surface to enhance its metallic and mechanical properties.

Study for surface pitting of a guide roller at combined sizing blocks using the ultrasonic processing method

This paper discusses how roller marks resulting from compact sizing block form on guide rollers and presents methods to reduce these marks. Ultrasonic nanocrystal surface modification (UNSM) is generally applied to reduce roller marks and improve wear resistance. UNSM treatment improves roller surface hardness, ensures wear resistance, and extends life cycle. This study confirmed that the minimum roller threshold hardness value for preventing surface defects must be 56 HRc. In addition, this study presents the UNSM processing conditions that can produce the maximum effect with the minimum amount of time for guide rollers that are being used without any surface modification. These conditions confirmed that the time required for guide roller inspections can be reduced by 50% or more. The applicability of this method can be expanded to various fields related to steel-making operations.

Numerical and Experimental Studies on Subscale Behaviors of Ultrasonic Surface Peening

Displacement-controlled and force-controlled surface-striking conditions were applied for finite element method simulations of the single path ultrasonic nanocrystal surface modification (UNSM) surface peening process. The single path UNSM treatment was done on a 4 mm-thick 6061 T6 Al sheet, and the surface topology and through-thickness residual stresses were measured and compared to the simulation results. Both displacement- and force-controlled simulations predicted maximum compressive residual stresses near the surface and subsurface for the stresses along the strike progression direction and transverse direction, respectively. The experimentally measured through-thickness residual stress profile also showed the maximum compressive residual stress near the subsurface. Both simulation conditions showed a topological pile-up on the surface in front of the leading strike. However, only the force-controlled simulation showed the pile-up breakdown at a critical number of strikes followed by the redistribution of subsurface strain fields, and lead to topological undulations along the edge and valley of the UNSM path, which were confirmed to be consistent with the surface topology measured from the experiment. It was concluded that the actual UNSM strike is close to the force-controlled surface-striking condition.

Surface nanocrystallization by ultrasonic nano-crystal surface modification and its effect on gas nitriding of Ti6Al4V alloy

The effects of Ultrasonic Nanocrystal Surface Modification (UNSM) on the gas nitriding behavior of Ti6Al4V alloy have been investigated. Gas nitriding was performed at 700 and 800 °C. The microstructure after UNSM and gas nitriding was characterized using X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Microstructural investigations revealed the formation of an approximately 10 µm thick severe plastic deformation layer as well as nano-grains after UNSM treatment. The UNSM-treated Ti6Al4V alloy formed 0.26 µm and 1.35 µm thick nitride layers after nitriding at 700 °C and 800 °C, respectively, and UNSM resulted in an increased layer thickness relative to untreated samples at both temperatures. The results suggest that nitrogen adsorption and reaction capability were enhanced in the UNSM-treated Ti6Al4V alloy. This enhancement can be attributed to high-density dislocations and grain boundaries that were introduced by UNSM and served as efficient channels for nitrogen diffusion.

Simultaneous grain refinement and nanoscale spinodal decomposition of β phase in Ti-Nb-Ta-Zr alloy induced by ultrasonic mechanical impacts

It was found that ultrasonic nanocrystal surface modification (UNSM) treatment performed on Ti-Nb-Ta-Zr (TNTZ) alloy surface to produce a gradient nanostructured surface layer also resulted in the nano-scale spinodal decomposition of β phase. For the first time, nano-scale spinodal decomposition of β phase induced by ultrasonic mechanical impacts was observed in a short time without any age treatment. The peak shift of XRD to lower angles, (110) β XRD peak splitting, overlapped and asymmetric XRD peaks, satellite reflections in the SAED pattern, and lattice straining in HR-TEM images confirmed nano-scale spinodal decomposition of β phase in the TNTZ alloy induced by UNSM treatment. Nano-scale EDS line-scan probe analysis revealed the β phase separation into nano-scale domains of Ti-rich (β1) and Ti-depleted (β2) phases. HR-TEM images showed the semi-coherent arrangement of Ti-rich (β1) and Ti-depleted (β2) regions. Nanosized grain formation and spinodal decomposition of β phase were induced simultaneously by UNSM treatment. The nano-scale grains, high dislocation density, and semi-coherent interface between the spinodally separated phases contributed to the high hardness of the UNSM-treated TNTZ alloy specimen.

Wear resistance and adhesive failure of thermal spray ceramic coatings deposited onto graphite in response to ultrasonic nanocrystal surface modification technique

In this study, thermal spray ceramic (TSC) coatings sprayed onto a graphite were subjected to ultrasonic nanocrystal surface modification (UNSM) technique. The surface roughness of the as-received Cr3C2, ZrO2 and Al2O3 coatings was reduced by about 28, 24 and 9% after UNSM treatment, which can be explained that the high peaks were removed during UNSM treatment, where a flat surface area is enlarged due to the partially elimination of single- and interconnected micro-pores. In addition, the number of cracks is also reduced by filling up the cracks by a smashed coating powder due to the continuous high-frequency strikes of a tip to the surface of the coating resulting in increase in surface hardness of the as-received Cr3C2, ZrO2 and Al2O3 coatings by about 14, 10 and 6% after UNSM treatment, respectively. The wear resistance and adhesive failure of the coatings were improved after UNSM treatment as well representing a remarkable influence on the friction and wear performance, and the critical load of the coatings. Hence, it is expected that a hybrid use of TSC coatings with UNSM technique is beneficial to improving the surface and adhesion behavior of the coatings to be applied to a graphite mold to produce a glass.

Effects of ultrasonic nanocrystal surface modification on the wear and micropitting behavior of bearing steel in boundary lubricated steel-steel contacts

An ultrasonic nanocrystal surface modification (UNSM) technique has been used to treat AISI 52100 steel specimens and thrust ball bearing raceways. Tribological performances of untreated specimens were compared to UNSM-treated specimens in reciprocating sliding and rolling/sliding contact under boundary lubricated conditions. Friction and wear coefficients, micropitting, and changes in surface profiles and surface roughness of the specimens were studied. Results showed that UNSM treated specimens had higher wear and micropitting resistance than the untreated specimens. The improvements in wear and micropitting resistance may be attributed to increased surface hardness, refined grain sizes and compressive residual stress near surface region as a result of UNSM treatment. The UNSM technique has been proven to be a powerful tool to improve the durability and tribological performance of contacting surfaces of mechanical components such as bearings, gears, and seals.

Influence of Ultrasonic Nanocrystal Surface Modification on the Corrosion and Stress Corrosion Cracking Behavior of Low Carbon Steel (ASTM A139) Welded Joint in the Simulated District Heating Environment

The effect of ultrasonic nanocrystal surface modification (UNSM) on the corrosion and stress corrosion cracking behavior of low carbon steel (ASTM A139) welded joint in the simulated district heating water (internal heating water) were investigated. After UNSM treatment, the microstructures of welded joint were transformed from the grain boundary ferrite and widmanstätten ferrite to polygonal ferrite accompanied by grain refinement. In electrochemical tests, the corrosion resistance of the welded joint was increased after UNSM treatment as a result of the grain refinement and improved stability of the oxide film. The stress corrosion cracking behavior was measured by slow strain rate tests with accelerated anodic and cathodic reactions. The results indicated that the UNSM treatment had a significant effect on the corrosion condition, whereas UNSM had no effect on hydrogen embrittlement.

The effects of ultrasonic nanocrystal surface modification on the fatigue performance of 3D-printed Ti64

3D-printed metals have great potential for application in the biomedical and the aerospace industries. Unfortunately, they suffer from poor surface finish, high porosity, and high tensile residual stresses, leading to inferior mechanical properties as compared with traditional cast or wrought metals. In this study, we introduce an innovative method, ultrasonic nanocrystal surface modification (UNSM), for the processing of a 3D-printed Ti-6Al-4V alloy. The surface finish, microstructure, residual stresses and mechanical properties of the samples before and after UNSM treatment were characterized and compared. It was found that the UNSM treatment resulted in much better surface finish, lower subsurface porosity, and a high magnitude of compressive residual stresses, leading to significant improvement in rotation bending fatigue performance.

Nanostructured β-type titanium alloy fabricated by ultrasonic nanocrystal surface modification

The surface of β-type Ti-Nb-Ta-Zr (TNTZ) alloy, which is a promising material for biomedical applications, was treated with the ultrasonic nanocrystal surface modification (UNSM) technique to enhance its hardness. As a result, a gradient nanostructured (GNS) layer was generated in the surface; the microstructure of the top surface layer consisted of nanoscale lamellae with a width of about 60–200nm. In addition, there were lamellar grains consisting of nanostructured subgrains having unclear and wavy boundaries. The treated surface exhibited a hardness value of ∼385HV compared to 190HV for the untreated alloy. It was further determined that highly dense deformation twins were generated at a depth of ∼40–150µm below the UNSM-treated surface. These deformation twins led to a significant work hardening effect which aided in enhancing the mechanical properties. It was also found that UNSM treatment resulted in the formation of micropatterns on the surface, which would be beneficial for high bioactivity and bone regeneration performance of TNTZ implants.