Ultrasonic Nanocrystalline Surface Modification Technique Research Articles

High Strength and Wear Resistance of Tantalum by Ultrasonic Nanocrystalline Surface Modification Technique at High Temperatures

Enhancing the strength of materials is of great concern in that the failures such as wear, corrosion and fatigue occur on the surface. A tantalum (Ta), which is a refractory metal, was subjected to severe plastic deformation induced by ultrasonic nanocrystalline surface modification (UNSM) technique at room- and high-temperatures of 200°C and 800°C. The mechanical properties and wear resistance of Ta before and after UNSM treatment were characterized by X-ray diffraction (XRD), hardness tester, and ball-on-disk tribometer, respectively. The UNSM treatment at 800°C led to the intensity reduction and broadening, and the diffraction peaks were shifted to lower angles, which means the presence of compressive residual stress and grain size refinement. The hardness of the UNSM-treated sample at room temperature was higher than that of the untreated one, and it was further increased with increasing the UNSM treatment temperature. In addition, the effect of UNSM treatment at high-temperature on wear resistance was significant than that of the UNSM treatment at room-temperature. We demonstrate the possibility of further increasing the mechanical properties and wear resistance of Ta by UNSM treatment at high-temperatures in comparison with the untreated and UNSM-treatment at room temperature, which would be beneficial for applications of Ta.

Friction and Wear Reduction of Eccentric Journal Bearing Made of Sn-Based Babbitt for Ore Cone Crusher.

An anti-friction Babbitt alloy-coated bearing made by a casting process is a journal bearing, which is used in an ore cone crusher eccentric. The main purpose of the Babbitt coated eccentric is to provide a low friction to support and guide a rotating shaft. Despite the fact that the Babbitt-coated eccentric offers a low friction coefficient and can be operated without a continuous supply of lubricant, it suffers from mining environments and short service life. In this study, an ultrasonic nanocrystalline surface modification (UNSM) technique was used to further reduce the friction coefficient, to increase the wear resistance, and to extend the service life of the Sn-based Babbitt metal. The friction and wear behavior of the Sn-based Babbitt metal was investigated using a block-on-ring tester under both dry and oil-lubricated conditions. The results of the experiments revealed that the friction and wear behavior of Sn-based Babbitt metal could be improved by the application of the UNSM technique. The friction and wear mechanisms of the specimens were explained and discussed in terms of changes in surface properties—microstructure, surface hardness, surface roughness, etc.

Microstructural Characterization and Mechanical Properties of Stainless Steel Inlay Welded Dissimilar Materials

This present work was carried out to characterize the microstructure and mechanical properties of austenitic stainless steel (SS) 316L to dissimilar welding of Inconel 52 and Inconel 82 fillers that were treated by ultrasonic nanocrystalline surface modification (UNSM) technique. The microstructure and hardness map of the specimens were characterized by optical microscope (OM) and micro-hardness tester. The increase in hardness and refinement in grain size after UNSM treatment were found for the SS 316L/52 and SS 316L/82. In addition, the induced compressive residual stress in the surface layer of base SS 316L was measured. It is expected that the increased hardness into several microns in depth and modified microstructure with a severe plastically deformed surface layer by UNSM technique can increase the resistance to corrosion and extend the service life of pressurized water reactors (PWRs).

Microstructure and Friction Behavior of AISI 52100 and D2 Steels Subjected to Ultrasonic Nanocrystalline Surface Modification (UNSM) Technique at a High Temperature

In this study, two different AISI 52100 bearing and D2 tool steels were subjected to ultrasonic nanocrystalline surface modification (UNSM) technique at ambient and high temperature of 500 °C. The objective of this study is to characterize the microstructure and to investigate the effectiveness of UNSM technique on the friction and wear behavior of those steels. The friction and wear behavior of the specimens against AISI52100 bearing steel ball with a diameter of 10 mm was carried out using a micro-tribo tester under dry conditions. The hardness with respect to depth from the top surface was measured using a microhardness. The change in the microstructure of the specimens before and after UNSM treatment was characterized by scanning electron microscopy (SEM). The findings from this preliminary study are expected to be implemented to the bearings and tools to increase the efficiency and performance of the components.

Low friction and high strength of 316L stainless steel tubing for biomedical applications

We propose herein a nondestructive surface modification technique called ultrasonic nanocrystalline surface modification (UNSM) to increase the strength and to improve the tribological performance of 316L stainless steel (SS) tubing. Nanocrystallization along nearly the complete tube thickness of 200μm was achieved by UNSM technique that was confirmed by electron backscatter diffraction (EBSD). Nano-hardness of the untreated and UNSM-treated specimens was measured using a nanoindentation. Results revealed that a substantial increase in hardness was obtained for the UNSM-treated specimen that may be attributed to the nanocrystallization and refined grains. Stress-strain behavior of the untreated and UNSM-treated specimens was assessed by a 3-point bending test. It was found that the UNSM-treated specimen exhibited a much higher strength than that of the untreated specimen. In addition, the tribological behavior of the untreated and UNSM-treated specimens with an outer diameter (OD) of 1.6mm and an inner diameter (ID) of 1.2mm was investigated using a cylinder-on-cylinder (crossed tubes of equal radius) tribo-tester against itself under dry conditions at ambient temperature. The friction coefficient and wear resistance of the UNSM-treated specimen were remarkably improved compared to that of the untreated specimen. The significant increase in hardness after UNSM treatment is responsible for the improved friction coefficient and wear resistance of the tubing. Thus, the UNSM technique was found to be beneficial to improving the mechanical and tribological properties of 316L SS tubing for various potential biomedical applications, in particular for coronary artery stents.

The possibility of reducing the reflectance and improving the tribological behavior of Si wafer by UNSM technique

In this study, mono- and poly-crystalline Si wafers, which are widely used in the manufacturing of high-performance solar cells, and nano- and micro-electromechanical systems (NEMS/MEMS), were subjected to ultrasonic nanocrystalline surface modification (UNSM) technique. The reflectance property of mono-crystalline Si wafer was improved after UNSM treatment in a certain wavelength but it reduced remarkably for poly-crystalline Si wafer. The hardness of both Si wafers was increased after UNSM treatment resulting in improvement of tribological behavior. According to the results of the present study, a UNSM technique might be considered as an alternative surface modification process to improve the properties of Si wafers for solar cell and NEMS/MEMS applications.

Friction Reduction and Wear Resistance Enhancement of SiC and Si3N4 Ceramics under Dry Conditions

ABSTRACTIn this study, an effort was made to control the friction and wear behavior of silicon carbide (SiC) and silicon nitride (Si3N4) ceramics using an ultrasonic nanocrystalline surface modification (UNSM) technique. The friction and wear behavior of the ceramic specimens was investigated using a ball-on-disk tribotester under dry conditions against two different Si3N4 and bearing steel (SUJ2) balls. The experimental test results revealed the possibility of controlling the friction and wear behavior of ceramics, where the friction coefficient and wear resistance of the specimens were improved by the UNSM technique. The hardness of the specimens also increased after UNSM treatment, but it decreased abruptly with increasing depth from the very top surface. Microscratch tests showed that the critical load of the specimens was improved by the UNSM technique. In addition, Raman spectra results revealed that no additional phase was detected after UNSM treatment, but the intensity decreased after UNSM treatment. Hence, the UNSM technique ensures stronger ceramics and enables better friction and wear behavior than available conventional sintered ceramics.

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.

Wear and Adhesive Failure of Al2O3 Powder Coating Sprayed onto AISI H13 Tool Steel Substrate

In this study, an alumina (Al2O3) ceramic powder was sprayed onto an AISI H13 hot-work tool steel substrate that was subjected to sanding and ultrasonic nanocrystalline surface modification (UNSM) treatment processes. The significance of the UNSM technique on the adhesive failure of the Al2O3 coating and on the hardness of the substrate was investigated. The adhesive failure of the coating sprayed onto sanded and UNSM-treated substrates was investigated by a micro-scratch tester at an incremental load. It was found, based on the obtained results, that the coating sprayed onto the UNSM-treated substrate exhibited a better resistance to adhesive failure in comparison with that of the coating sprayed onto the sanded substrate. Dry friction and wear property of the coatings sprayed onto the sanded and UNSM-treated substrates were assessed by means of a ball-on-disk tribometer against an AISI 52100 steel ball. It was demonstrated that the UNSM technique controllably improved the adhesive failure of the Al2O3 coating, where the critical load was improved by about 31%. Thus, it is expected that the application of the UNSM technique to an AISI H13 tool steel substrate prior to coating may delay the adhesive failure and improve the sticking between the coating and the substrate thanks to the modified and hardened surface.

Microstructural evolution and surface properties of nanostructured Cu-based alloy by ultrasonic nanocrystalline surface modification technique

A nanostructured surface layer with a thickness of about 180μm was successfully produced in Cu-based alloy using an ultrasonic nanocrystalline surface modification (UNSM) technique. Cu-based alloy was sintered onto low carbon steel using a powder metallurgy (P/M) method. Transmission electron microscope (TEM) characterization revealed that the severe plastic deformation introduced by UNSM technique resulted in nano-sized grains in the topmost surface layer and deformation twins. It was also found by atomic force microscope (AFM) observations that the UNSM technique provides a significant reduction in number of interconnected pores. The effectiveness of nanostructured surface layer on the tribological and micro-scratch properties of Cu-based alloy specimens was investigated using a ball-on-disk tribometer and micro-scratch tester, respectively. Results exhibited that the UNSM-treated specimen led to an improvement in tribological and micro-scratch properties compared to that of the sintered specimen, which may be attributed to the presence of nanostructured surface layer having an increase in surface hardness and reduction in surface roughness. The findings from this study are expected to be implemented to the automotive industry, in particular connected rod bearings and bushings in order to increase the efficiency and performance of internal combustion engines (ICEs).

UNSM 기술을 이용한 초경의 기계적 특성변화

In this study, an ultrasonic nanocrystalline surface modification (UNSM) technique is applied to tungsten carbide-cobalt (WC-Co) to extend the service life of carbide parts used in press mold. The UNSM technique modifies the structure, reduces the surface roughness, increases the surface hardness, induces the compressive residual stress, and increases the wear resistance of materials by introducing severe plastic deformation. The surface roughness, hardness, and compressive residual stress of WC after UNSM treatment improve by about 42, 10, and 71%, respectively. A wear test under dry conditions is used to assess the effectiveness of the UNSM technique on the friction and wear behavior of WC. The UNSM technique is found to reduce the WC friction coefficient by approximately 21% and enhance the wear resistance by approximately 85%. The improved friction and wear behavior of WC may be mainly attributed to the increased hardness and compressive residual stress. Moreover, the WC specimen is treated by UNSM technique using three different WC, silicon nitride (Si3N4) and stainless steel (STS304) balls. The surface treated by WC balls shows the highest hardness when compared with treatment by stainless steel and silicon nitride balls. According to the obtained results, the UNSM technique is believed to increase the durability of the carbide component by improving the friction and wear behavior.

Wear mechanisms of silicon carbide subjected to ultrasonic nanocrystalline surface modification technique

A modified surface layer with a thickness of about 4µm was produced at the top surface of sintered silicon carbide (SiC) by ultrasonic nanocrystalline surface modification (UNSM) technique. The objective of this study is to investigate the effectiveness of modified surface layer on the tribological properties and to give insight into the wear mechanisms of SiC. The tribological properties of the untreated and UNSM-treated SiC disk specimens against silicon nitride (Si3N4) ceramic ball were investigated using a ball-on-disk tribometer at normal loads of 1 N, 5 N and 10 N under water-lubricated conditions. Results revealed that the friction coefficient was found to be 0.08 and 0.065 for the untreated and UNSM-treated specimens at a normal load of 1 N which may be attributed to the modified surface layer at the top surface having higher hardness and smoother roughness with a small number of porosity, respectively. This reduction in friction coefficient enables to reduce energy consumption of water-based tribological systems. Wear track analysis was conducted using a nanoscale hybrid microscopy (NHM). NHM images showed that severe polishing and grooving marks were observed on the untreated specimen, while only mild grooving marks were observed on the UNSM-treated specimen. It was also confirmed that the UNSM technique changes the wear mechanisms of SiC: oxidative-adhesive-abrasive-micro fracture wear takes place in the untreated specimen, while adhesive-abrasive wear takes place in the UNSM-treated specimen. Application of UNSM technique would be highly advantageous for water-lubricated ceramic bearings.

The usability and preliminary effectiveness of ultrasonic nanocrystalline surface modification technique on surface properties of silicon carbide

Abstract This study reports the change in microstructural, mechanical and tribological characteristics of sintered silicon carbide (SiC) ceramic subjected to ultrasonic nanocrystalline surface modification (UNSM) technique. The surface microstructure of the untreated and UNSM-treated specimens was examined by SEM, EDS and XRD. The mechanical properties of the specimens were measured by nanoindentation. The tribological properties of the specimens were assessed using a ball-on-disk tribometer against a bearing steel (SAE52100) ball at two different temperatures under dry reciprocating conditions. It was confirmed by SEM that the UNSM-treated specimens had much denser microstructure than those of the untreated specimens. The EDS results revealed that the UNSM technique has no effect on the chemical composition of sintered SiC ceramic. The average surface roughness obtained by AFM was found to be about 83.6 nm and 60.1 nm for the untreated and UNSM-treated specimens, respectively. The tribological results showed that the UNSM-treated specimens exhibited a lower friction coefficient and higher wear resistance compared to those of the untreated specimens. In addition, it was found that the UNSM technique was able to decrease the quantity of pores. The results of this study are expected to make sintered SiC ceramic more attractive for numerous applications in various industries.

Enhancement in wear resistance of sintered silicon carbide at various temperatures

In this study, the mechanical and tribological properties of sintered silicon carbide (S-SiC) subjected to ultrasonic nanocrystalline surface modification (UNSM) technique were investigated. The tribological properties of the untreated and UNSM-treated specimens were assessed using a ball-on-disk tribometer against an alumina (Al2O3) ball at various temperatures under oil-lubricated conditions. The results indicated that the UNSM-treated specimen exhibited better tribological properties compared to that of the untreated specimen. Scratch tests were also performed on these specimens. The surface roughness obtained using an atomic force microscope (AFM) was found to be 101.7nm and 81.9nm for the untreated and UNSM-treated specimens, respectively. It was also found that the UNSM technique was beneficial for a decrease in quantity of pores.

Effects of ultrasonic nanocrystalline surface modification (UNSM) technique on the tribological behavior of sintered Cu-based alloy

This paper presents the effects of ultrasonic nanocrystalline surface modification (UNSM) technique on the tribological behavior of sintered Cu-based alloy prepared using a powder metallurgy (P/M) technique. The tribological behavior of the untreated and UNSM-treated specimens was investigated using a ball-on-disk reciprocating tribometer against a bearing steel ball under dry and oil-lubricated conditions. Results revealed that the UNSM-treated specimens led to a lower friction coefficient and higher wear resistance compared to the untreated specimens. The obtained results demonstrated the beneficial effects of UNSM technique. It is expected that the results of this study may be implemented to the automotive industry with the aim of improving the durability of internal combustion engine (ICE) parts which are made of Cu-based bimetal strips.

Improvement of the tribological properties of Al6061–T6 alloy under dry sliding conditions

The tribological properties of ultrasonic nanocrystalline surface modification (UNSM) treated Al6061–T6 alloy were investigated at various normal loads under dry sliding conditions. Electron backscattering diffraction (EBSD) analysis revealed a microstructure alteration of about 70μm in thickness generated by the UNSM technique. The friction test results showed that the friction coefficient and wear rate of the UNSM-treated specimen reduced by about 25 and 20% compared to that of the UNSM-free specimen, respectively. X-ray photoelectron spectroscopy (XPS) results showed that the oxide percentage on the worn surface increased, but that of carbon percentage decreased after the UNSM treatment.

Frictional Behavior of Duplex Nano-corrugated and Nanostructured Cu Alloy Produced by UNSM

In this study, a duplex nano-corrugated and nanostructured surface was produced using an ultrasonic nanocrystalline surface modification (UNSM) technique. The objective of this study is to demonstrate the ability of UNSM technique to produce a desired nano-corrugated and nanostructured surface in order to improve the frictional behavior of Cu alloy. The experimental friction test results showed that the UNSM-treated specimen led to a lower friction coefficient compared to the untreated specimen, which may be attributed to the effects of UNSM technique.