Ultrasonic Nanocrystal Surface Modification Technique Research Articles

Effect of surface modification technology on mechanical properties and dry fretting wear behavior of Inconel 718 alloy fabricated by laser powder-based direct energy deposition

Ultrasonic nanocrystal surface modification (UNSM) technique was applied to Inconel 718 alloy fabricated by laser powder-based direct energy deposition (LP-DED). The main aim of this study is to improve the mechanical properties and fretting wear behavior. No significant difference in surface roughness between the polished and UNSM-treated samples was made on purpose to avoid the effect of surface roughness on fretting wear behavior. The hardness and residual stress of the polished samples were increased after UNSM technique. Dry fretting wear behavior was evaluated using a ball-on-disk configuration at 24 and 60 °C. The results showed that the fretting wear resistance of the polished samples at both temperatures was enhanced, whereas an increase in temperature further enhanced the fretting wear resistance. In addition, possible factors influencing the enhancement in fretting wear behavior after UNSM technique in terms of fretting wear mechanisms and potential application were discussed.

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.

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.

Experimental Investigation on Friction and Wear Behavior of the Vertical Spindle and V-belt of a Cotton Picker.

This study deals with the friction and wear behavior of the vertical spindle and V-belt to improve the reliability, operation and to extend the service life of a cotton picker. The vertical spindle made of low-carbon steel (ST3) was treated by the ultrasonic nanocrystal surface modification (UNSM) technique to control the friction and wear behavior. It was found that the UNSM technique reduced surface roughness and increased surface hardness of the vertical spindle. The friction and wear behavior of the vertical spindle and V-belt was assessed by carrying out tribological tests and the results showed that the UNSM-treated vertical spindle generated a higher friction coefficient compared to the untreated one due to having less slip. In case of wear resistance, unmeasurable wear occurred on the surface of the vertical spindle due to its significant high hardness compared to the hardness of the V-belt that came into contact with the vertical spindle in relative motion. Hence, the wear behavior and mechanisms of the V-belts were systematically investigated and also discussed based on the wear track profiles and micrographs. It can be concluded that the application of the UNSM technique to the vertical spindle may contribute to improve the performance of cotton pickers by reducing the slip and prolonging the service life.

Lowering friction of ball screws made of different steel grades through ultrasonic impact treatment

Abstract Ball screws made of SCM445H, NF42CD4 and SAE4150 steel grades were treated by ultrasonic nanocrystal surface modification (UNSM) technique to boost their performance by improving the surface integrity and lowering the friction. It was found that the friction of the UNSM-treated ball screws reduced successfully thanks to the improvement in surface integrity, transformation of tensile residual stress into compressive residual stress. Suggested mechanisms concerning lowering the friction of ball screws were discussed. Consequently, the feasible possibility of adopting the UNSM technique to a ball screw in order to improve its performance and reliability through lowering the friction was systematically investigated. Accordingly, the application of UNSM technique is a crucial approach to determine the replacement of those three different steel grades.

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.

Effect of Ultrasonic Surface Impact on the Fatigue Behavior of Ti-6Al-4V Subject to Simulated Body Fluid

The effect of ultrasonic nanocrystal surface modification (UNSM) on the fatigue behavior of Ti6Al4V (TC4) in simulated body fluid (SBF) was investigated. UNSM with the condition of a static load of 25 N, vibration amplitude of 30 μm and 36,000 strikes per unit produced about 35 μm surface severe plastic deformation (SPD) layers on the TC4 specimens. One group was treated with a hybrid surface treatment (UNSM + TiN film). UNSM technique improves the micro hardness and the compressive residual stress. The surface roughness is increased slightly, but it can be remarkably improved by the TiN film. The fatigue strength of TC4 is improved by about 7.9% after UNSM. Though the current density of corrosion is increased and the pitting corrosion is accelerated, UNSM still improved the fatigue strength of TC4 after pre-soaking in SBF by 10.8%. Interior cracks initiate at the deformed carbide and oxide inclusions due to the ultrasonic impacts of UNSM. Corrosion products are always observed at the edge of fracture surface to both interior cracks and surface cracks. Coating a TiN film on the UNSMed surface helps to improve the whole properties of TC4 further.

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.

Strengthening of Ti-6Al-4V alloy by high temperature ultrasonic nanocrystal surface modification technique

Ti-6Al-4V alloy was subjected to heat treatment with (w/) and without (w/o) ultrasonic nanocrystalline surface modification (UNSM) treatment. The diffraction peaks of heat treatment w/o UNSM treatment samples were shifted to higher angles due to the tensile stress, while the heat treatment w/ UNSM treatment samples led to the intensity reduction and broadening, and the shift to lower angles, which may be attributed to the compressive residual stress, which increased with increasing the temperature. However, the peaks of heat treatment w/ UNSM treatment sample at 400°C were shifted to higher angles. This unusual behavior of the alloy is associated with a high tensile stress of α phase.

The Effects of Ultrasonic Nanocrystal Surface Modification Technique Temperature on Microstructure and Wear of Alloy 600

Alloy 600 (UNS N06600) is an austenitic nickel-based alloy with superior corrosion resistance and high-temperature endurance, which determines its widespread applications in aeronautical, aerospace, marine and nuclear industries. Particularly, a number of nuclear components used Alloy 600 as their structure materials due to their high corrosion resistance, high-temperature endurance and excellent fabricant characteristics. Many failures have occurred in Alloy 600 with various forms of environmental degradations during long-term operation. In this study, an ultrasonic nanocrystal surface modification (UNSM) technique was applied to Alloy 600 at a room and a high temperature of 500 OC. The effects of UNSM treatment temperature on the microstructure and wear behavior including a compressive residual stress were investigated. The hardness, compressive residual stress with respect to depth from the top surface were measured. Also, the wear behavior of UNSM-treated at a room and a high temperature Alloy 600 specimen was compared to that of the untreated specimen. The increase in wear resistance by UNSM technique was discussed in terms of increased hardness, refined grain size and induced compressive residual stress.

A Preliminary Study on Hybrid Use of Thermal Spray Coating and Ultrasonic Nanocrystalline Surface Modification Technique on the Tribological Properties of Yttria-Stabilized Zirconia Coating

An ultrasonic nanocrystal surface modification (UNSM) technique was applied to a thermally sprayed yttria-stabilized zirconia (YSZ) ceramic coating deposited onto a hot tool steel substrate to improve the mechanical and tribological properties. The friction test results showed that the UNSM-treated coating had a smoother surface, a lower friction, and a higher resistance to wear compared to that of the as-sprayed coating. It was also demonstrated that the UNSM technique improved the adhesion behavior of the coating by about 24%. Hence, it was found that a hybrid use of thermal spray coating (TSC) and UNSM technique is a meaningful way to bring together synergy effect of two emerging surface technologies in terms of tribology.

Ultrasonic fatigue performance of high temperature structural material Inconel 718 alloys at high temperature after UNSM treatment

AbstractThis study investigates the influence of ultrasonic nanocrystal surface modification (UNSM) technique on the mechanical characteristics and fatigue life of two types of annealed and aged Inconel 718 alloys. The mechanical properties of both UNSM‐treated alloys were compared with the untreated specimens. The fatigue life of the untreated and UNSM‐treated Inconel 718 alloy specimens was investigated by ultrasonic fatigue and rotary‐bending fatigue tests. Results revealed that the UNSM‐treated specimens exhibited longer fatigue life than those of the untreated specimens. The improvement in fatigue life is mainly attributed to the induced compressive residual stress induced in the subsurface by UNSM technique.

Rotary bending fatigue properties of Inconel 718 alloys by ultrasonic nanocrystal surface modification technique

This study investigates the influence of ultrasonic nanocrystal surface modification (UNSM) technique on fatigue properties of SAE AMS 5662 (solution treatment) of Inconel 718 alloys. The fatigue properties of the specimens were investigated using a rotary bending fatigue tester. Results revealed that the UNSM-treated specimens showed longer fatigue life in comparison with those of the untreated specimens. The improvement in fatigue life of the UNSM-treated specimens is attributed mainly to the induced compressive residual stress, increased hardness, reduced roughness and refined grains at the top surface. Fractured surfaces were analysed using a scanning electron microscopy (SEM) in order to give insight into the effectiveness of UNSM technique on fracture mechanisms and fatigue life.

A comprehensive review of nanostructured materials by ultrasonic nanocrystal surface modification technique

Nanostructured materials (NMs) possess outstanding properties than conventional coarse-grained (CG) materials. Hence designing potentially cost-efficient and environmentally products made of NMs with better are on high demand. This paper gives a comprehensive review of the most recent progress in production, characterisation and fundamental understanding of NMs produced by ultrasonic nanocrystal surface modification (UNSM) technique. In this review, we demonstrate a detailed description of the literature on the subject as well as highlight challenges for the production of NMs. Recently, this technique has also been applied to thermal spray ceramic coatings and the newly obtained experimental results are also discussed.

초음파나노표면개질 기술을 적용한 초경의 기계적특성 및 마모 연구

In this study, we investigated the effectiveness of an ultrasonic nanocrystal surface modification (UNSM) technique on the mechanical and wear properties of tungsten carbide (WC). The UNSM technique is a newly developed surface modification technique that increases the mechanical properties of materials by severe plastic deformation. The objective of this study was to improve the wear resistance of press die made of WC by applying the UNSM technique. We observed the microstructures of the untreated and UNSM-treated specimens using a scanning electron microscope (SEM), and energy-dispersive X-ray spectroscopy (EDX) was used to investigate the chemical composition. The SEM observations showed the pore size and the number of pores decreased after the UNSM treatment. We assessed the wear behavior of both the untreated and UNSM-treated specimens using a scratch test. The test results showed that the wear resistance of the UNSM-treated specimens increased by about 46% compared with the untreated specimens. This may be attributed to increased hardness, reduced surface roughness, induced compressive residual stress, and refined grain size following the application of the UNSM technique. In addition, we found that the UNSM treatment increased the carbon concentration to 63% from 33%. We expect that implementing the findings of this study will lead to an increase in the life of press dies.

자동조심 롤러 베어링의 재제조 공정 및 피로수명 향상

Dept. of Mechanical Engineering, Sun Moon University, Asan 336-708, Korea(Received; Setpember 23, 2014 Revised; November 2, 2014; Accepted; November 5, 2014)Abstract − This study proposes a sustainable bearing remanufacturing process using the ultrasonic nanocrystalsurface modification (UNSM) technique. The UNSM technique is a newly developed and sophisticated surfacemodification technique that can increase the mechanical properties and improve the friction and wear per-formance of materials. Taking advantage of the bearing manufacturing process is the most significant way ofoptimizing the life of a bearing. The proper maintenance and usage of repaired bearings can increase their lifeto be equal to or greater than that of new bearings. This paper discusses the restoration of certain mechanicalproperties of worn, damaged, and discarded bearings, and suggests a remanufacturing process for used bearings,which can impart them with a lifespan equivalent to that of new bearings. The most damaged part of the dis-carded bearings is the raceway, which is the site of accumulated fatigue. The existing polishing or barrel finishingprocesses can recover the accumulated fatigue only partially. Rolling contact fatigue tests performed on UNSM-treated new and used specimens polished after 4×10

Very high cycle fatigue characteristics of a chrome‐molybdenum steel treated by ultrasonic nanocrystal surface modification technique

ABSTRACTCharacterization of very high cycle fatigue (VHCF) performance is of significant issue for ensuring long‐term durability and reliability of machinery and structural components due to the growing industrial demands and significant requirements of the advanced systems. In this study, VHCF characteristics of nanocrystallized skins (nanoskin) on JIS SCM435 (AISI 4137) steels were investigated as three different nanoskins on the surface, which was fabricated by altering the static load of ultrasonic nanocrystal surface modification (UNSM) treatment. The fatigue characterization, which shows linearly proportional correlation in the range of 80–120 µm depth of subsurface, was subjected to severe plastic deformation by altering the static loads of UNSM treatment to 40, 70 and 100 N, respectively. The fatigue strength increased up to 30% in the regime of VHCF. The improved strength mainly resulted from the generation of nanocrystalline structure, the enhanced surface uniformity, hardness and residual stress.

Fatigue properties of a S45C steel subjected to ultrasonic nanocrystal surface modification

An ultrasonic nanocrystal surface modification (UNSM) technique, at 3 different vibration strike numbers (34,000 times/mm 2, 45,000 times/mm 2, 68,000 times/mm 2) was used to modify the surface structure and properties of S45C. These three process conditions respectively produced 2 μm, 12 μm and 30 μm nanocrystal layers. UNSM technique improves the following mechanical properties: microhardness, surface roughness, and compressive residual stress. Also, fatigue life increased with the vibration strike number. UNSM C3 (with the vibration strike number of 68,000 times/mm 2) has improved the fatigue strength by as much as 33% for S45C. Optical microscope pictures show that cracks usually initiate from intergranular microcracks on the surface and then extend along the tip traces of UNSM which are considered as process defects. A simple math model (tearing adhesive plaster model) has been made to analyze the initiation and growth of cracks. Though most of the cracks initiate at the surface of specimens, surface nanocrystal layers can help to retard crack initiation. In S45C, the efficiency of crack resistance is more than 48%.the vibration strike number