Micro-dimpled surface by ultrasonic nanocrystal surface modification and its tribological effects (original) (raw)
Related papers
Tribology Online, 2011
One of the conclusively presumed effects of micro-scale dimples under oil-lubricated conditions is that can serve as oil reservoirs and play a role in promoting the retention of a lubricating film. Ultrasonic nanocrystal surface modification (UNSM) technology is an emerging effective method for producing micro-scale dimples on a workpiece surface and improving the tribological performance of lubricated friction units. The main object of this research is to understand the effect of micro-scale dimple size on tribological characteristics under oil-lubricated sliding contacts. The current study investigated the effect of micro-scale dimple size on friction and wear reduction through micro-scale dimples. The tribological characteristics of silicon nitride ceramic (Si 3 N 4) ball and S45C carbon steel disk combination in a defined ball-on-disk configuration were determined. It was recognized that friction property has a connection with the size of micro-scale dimple. Overall micro-scale dimpled disk specimens showed better tribological properties in terms of reduced friction coefficient and wear volume loss comparing to the polished specimen.
Ultrasonic Nanocrystal Surface Modification Technology
Journal of Nanoscience and Nanotechnology, 2012
Ultrasonic nanocrystal surface modification (UNSM) technology is a novel surface modification technology that can improve the mechanical and tribological properties of interacting surfaces in relative motion. UNSM treatment was utilized to improve the wear resistance fatigue strength of slim bearing rings made of SAE52100 bearing steel without damaging the raceway surfaces. In this study, wear and fatigue results that were subjected to different impact loads of the UNSM treatment were investigated and compared with those of the untreated specimen. The microhardness of the UNSMtreated specimens increased by about 20%, higher than that of the untreated specimens. The X-ray diffraction analysis showed that a compressive residual stress of more than 1,000 MPa was induced after the UNSM treatment. Also, electron backscatter diffraction analysis was used to study the surface structure and nanograin refinement. The results showed that the rolling contact fatigue life and the rotary bending fatigue strength of the UNSM-treated specimens increased by about 80% and 31%, respectively, compared to those of the untreated specimen. These results might be attributed to the increased microhardness, the induced compressive residual stress, and the nanocrystal structure modification after the UNSM treatment. In addition, the fracture surface analysis showed that the fish eye crack initiation phenomenon was observed after the UNSM treatment.
The present research has been done to investigate the influence of the relative motion of a plane surface with the other having micro-circular dimples throughout the contact. Using pin-on-disk setup, experiments have been carried out to study the influence of micro-dimple area density on friction and specific wear rate at the interface of two materials. Circular dimples are distributed in spiral array on the disk face. Based on the experiments, better tribological results have been achieved in the starved boundary lubrication mode.
On Design and Tribological Behaviour of Laser Textured Surfaces
Procedia CIRP
The paper reports an investigation into the functional response of textured surfaces with different designs that incorporated arrays of microdimples and grooves (40μm diameter/width and 15μm depth for both patterns) produced on tungsten carbide (WC) blocks by employing nanosecond (ns) and femtosecond (fs) lasers. In particular, the tribological performance of the textured WC blocks against stainless steel (SS316L) counterbody was evaluated in terms of friction and wear under dry condition compared to an untextured specimen. Friction tests were carried out on a reciprocating sliding tester while unidirectional ball-on-disc method was utilised to assess wear on the mating surfaces. The untextured surface exhibited a continuous rise in the friction coefficient from 0.15 to 0.5 from the start of the cycle to the end while the specimens textured with ns and fs lasers reached steady-state condition after 100 and 200 cycles with values between 0.35-0.45 and 0.3-0.4, respectively. Energy dispersive spectroscopy following wear tests showed a pronounced material transfer from the balls to the textured surfaces with stainless steel filling up some of the dimple and groove cavities; however, the reverse phenomenon was not apparent. Additionally, texturing with the fs laser exhibited formation of nano-ripples/structures in the produced dimples and grooves that can be further studied for creating nano-textured cutting tools or surfaces with super-hydrophobic/anti-ice properties.
2011
Double row angular contact ball bearings (DRACBB) are capable of carrying high radial and thrust loads in both directions and need small space comparing to two single row angular contact bearings. A newly developed magnetic clutch of compressor needs higher dynamic load rating without increasing space for bearings. Therefore, Ultrasonic Nanocrystalline Surface Modification (UNSM) technology is applied to bearing raceways in order to improve rolling contact strength and to reduce friction loss. The rolling contact fatigue and friction test specimens which are treated by UNSM technology are performed in order to find proper surface hardness, topology and compressive residual stress. Comparison test of service life and friction coefficient between UNSM-treated and untreated bearings were carried out in the bearing test rig. After UNSM treatment, the friction coefficient was reduced and the service life was extended at room temperature due to the UNSM treatment. Life tests data showed t...
2011
Ultrasonic nanocrystal surface modification (UNSM) technology is a surface enhancement technology analogous to shot peening, laser shot peening (LSP), ultrasonic peening (UP), deep rolling (DR) and low plasticity burnishing (LPB). The UNSM utilizes ultrasonic vibration energy to maximize coverage and stress-field density. In this process, a tool-steel, tungsten carbide or ceramic ball is attached to an ultrasonic device and strikes the surface of a workpiece 20,000 to 40,000 times per second and 1,000 to 100,000 shots per square millimeter. The UNSM treatment induces deep compressive residual stress comparable to LSP and DR, but improves surface roughness not like other technologies and also produces a uniformly distributed micro dimples on the surface. Steel alloys, Cu alloys, Ti alloys and Al alloys are treated by UNSM and their mechanical properties are analyzed and compared before and after UNSM treatment.
Friction
An experimental investigation was performed for investigating the tribological performance of micro-dimple surface texture patterns on a cylindrical surface in a realistic operating environment of starved lubrication. Micro-dimples were generated by a dual-frequency surface texturing method, in which a high-frequency (16.3 kHz) three-dimensional (3D) vibration and a low-frequency (230 Hz) one-dimensional (1D) vibration were applied at the tool tip simultaneously, resulting in the generation of the hierarchical micro-dimples in a single step. Rotating cylinder-on-pin tribological tests were conducted to compare the tribological performance of the non-textured reference specimen and micro-dimple samples. The effect of surface textures generated with various shape parameters (long drop and short drop), dimension parameters (length and surface texture density), and operation parameters (load and sliding velocity) on the tribological performance was evaluated. Stribeck curves indicate th...
Wear, 2015
A modified surface layer with a thickness of about 4 mm 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 (Si 3 N 4) 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.