The paper contains the investigation results on the structure and phase composition of the laser radiation area (LRA) of the U8 and U10 steels over its entire thickness. In the present study, the ...laser surface hardening of both U8 (ASTM - W1-7) and U10 (ASTM - W1-9) steels in the air was performed by exploiting a quasi - CW fiber laser with a 130 W power and 3 mm/s processing speed. The phase composition of the oxide layer formed as a result of laser treatment (LT) in air, as well as the structure of the oxide-metal interface on the surface of U8 (ASTM–W1-7) and U10 (ASTM–W1-9) carbon tool steels were studied by X-ray photoelectron spectroscopy (XPS). It was established that the thickness of the completely oxidized surface layers for U8 and U10 steels is 38.7 nm and 99 nm, respectively.
The composition of the oxides of the steel surface after LT was determined. The presence of a wüstite-based film on U8 steel evidences the low wear properties of the LRA surface, while the thicker oxide layer of the modified U10 steel which contains Fe2O3 and Fe3O4 oxides with better strength properties, on the contrary, provides U10 steel surface with higher wear resistance. It was found that the wear rate of U10 steel modified surface decreases by more than two times, while the given value for U8 steel reduces no more than 17%. The paper reports the metallographic examination of the LRA structure. It was shown that the wear-resistant structural components that appeared after laser treatment lead to an increase in the deformation properties of steels. The maximum microhardness value of the LRA is 710 HV0.1 for U8 steel and 750 HV0.1for U10 steel.
•The surface of two carbon tool steels U8 (ASTM - W1-7) and U10 (ASTM - W1-9) was modified using laser radiation.•The elemental and phase composition of both steels in depth was studied by X-ray photoelectron spectroscopy.•Tribological tests have shown that thin oxide layers on the surface of modified steels affect the frictional properties of steels.•Metallographic studies have established that laser treatment leads to an increase in the deformation properties of steels.
The lapping and polishing operations are of the most important ones considering the finishing treatment of machine parts. These operations can be performed by numerous methods, among which the ...vibration-driven ones are of the most widespread. The present paper is focused on studying the dynamic behavior of the vibratory finishing machine providing the single-sided lapping and polishing of flat surfaces of cylindrical and prismatic parts. The major scientific novelty of this research consists in an improved control technique of generating the translational oscillations of the lapping (polishing) plates by means of implementing the double-magnet excitation system. In order to investigate the machine’s double-mass vibratory system dynamics, the corresponding mathematical model is developed using the Lagrange-d’Alembert principle. The numerical modeling is carried out with the help of the Mathematica software and presents the time dependencies of the lapping (polishing) plates kinematic parameters. The simplified experimental prototype of the vibratory lapping machine is developed and tested under different operational conditions. The proposed design ideas and obtained theoretical and experimental results can be effectively used by the designers of lapping and polishing equipment, as well as by the technologists implementing new techniques of finishing treatment.
The work addresses a particular case of interaction between adhesive and abrasive wear in the electrical contact field, characterized by a selective adhesive transfer layer. The system studied is ...composed of a resistive element (NiCr thin layer) and a contactor (AgPd), forming an angular position sensor lubricated with a standard silicone oil/PTFE grease. The angular position/electrical resistance relationship is disturbed by wear of the NiCr surfaces, enhanced by the formation on the AgPd contactor of a third body enriched in Ni. From a practical point of view, it has been found that this detrimental Ni-selective transfer formation can be controlled by inserting tumble finishing with lamellar alumina powder as the last step of NiCr track manufacturing. Acting like a solid lubricant, alumina clusters of 1–5 µm in size adhere to NiCr surface giving rise to a delay or cancel of Ni adhesion on the contactor which lead to a significant improvement of electrical behavior of the position sensor.
•We studied the wear mechanisms taking place in an electrical contact inside a sensor.•The resistance degradation of AgPd/NiCr contact is related to the wear process.•Selective transfer layer rich in nickel adhered on the AgPd surface is point out as the major factor limiting the electrical performances of the contact.•Tumble finishing treatment using Alumina particles was found to improve the electrical performances of the contact by stopping the growth of the transfer layer (3rd body).
Hardened layers on the surface of the steel 40X were obtained by combination of ultrasonic finishing treatment and high-intensity low-energy ion implantation of nitrogen ions. Using the optical ...metallography, X-ray diffraction and durometery methods the authors have studied the features of the structure and properties of surface layers. It is shown that nitride layer is formed on steel surface at implantation. This layer is a zone of internal nitriding; its phase composition is determined by the temperature of the implantation and by technique of surface pretreatment. The increase of nitriding temperature results in rising the nitriding phase in steel surface layer. Ultrasonic finishing treatment intensifies nitrogen ion implantation increasing the depth of the hardened layer by forming large number of crystal defects in the structure and improving micro-hardness by increasing the proportion of nitride phases.
Hardened layers on the surface of the steel 40X were obtained by combination of ultrasonic finishing treatment and high-intensity low-energy ion implantation of nitrogen ions. Using the optical ...metallography, X-ray diffraction and durometery methods the authors have studied the features of the structure and properties of surface layers. It is shown that nitride layer is formed on steel surface at implantation. This layer is a zone of internal nitriding; its phase composition is determined by the temperature of the implantation and by technique of surface pretreatment. The increase of nitriding temperature results in rising the nitriding phase in steel surface layer. Ultrasonic finishing treatment intensifies nitrogen ion implantation increasing the depth of the hardened layer by forming large number of crystal defects in the structure and improving micro-hardness by increasing the proportion of nitride phases.
Since the Coronavirus Disease 2019 (COVID-19) pandemic began, people have been wearing face masks for many hours every day. As these face masks are in contact with the skin, it is important to pay ...more attention to their quality and safety. This study examined the concentration of free formaldehyde in 90 non-medical face masks and related products (33 nonwoven, 30 woven cloth, 12 polyurethane, and 15 related products) because formaldehyde is a common contact allergen in textile products. For products consisting of mixed materials, each material was sampled, resulting in 103 samples for analysis. Free formaldehyde (34-239 μg/g) was found in three cloth masks, which consisted of cotton and polyester, with antibacterial and antiviral labeling. It was confirmed that the detected formaldehyde originated from the mask-finishing treatment by a hydrochloric acid extraction discrimination test. These masks may elicit contact dermatitis if the consumers have already been sensitized to formaldehyde. However, the risk of contact dermatitis caused by formaldehyde in masks may be considered low since the frequency of formaldehyde detection in masks in Japan is low.
Elements machined by laser and abrasive water jet cutting sometimes require the use of a finishing treatment. One of the finishing methods for machined elements is vibratory shot peening (VSP). This ...paper presents the influence of VSP technological conditions on the surface topography and surface roughness (parameters Ra and Rsk) of aluminium alloy AW-7075 samples. Experiments were carried out according to the following plan: first, vibratory shot peening (VSP) was conducted using balls with a diameter d = 3 mm, 6 mm and 9 mm. Then, the surfaces of the samples after VSP (treated with 6 mm diameter balls) were subjected to re-vibratory shot peening (RVSP). As a result of vibratory shot peening, the Ra parameter of the specimens after laser cutting decreased by 71% to 91%, while for the AWJ-treated elements it decreased by 56% to 85%. The additional operation decreased the Ra parameter in the entry zone by 4% to 6% for the samples after laser cutting and by 5% to 7% for the samples after AWJ, when compared to the Ra value after single vibratory shot peening conducted using balls with d=6 mm. After VSP and RVSP, the surface topography of the samples changed. Vibratory shot peening led to the creation of "striations" on the shot-peened surface that could not be completely removed. The re-vibratory shot peening operation (for specific conditions) had a positive effect on the geometric structure of the surface of the elements after cutting. Both VSP and RVSP caused reduction in the analysed 3D surface roughness parameters.
In this work, the characterization of combination herbal extracts of wild turmeric (WT) and holy basil (HB) and their synergistic effect on the antibacterial properties of finished single jersey ...knitted fabrics of cotton, lyocell and micro-denier polyester were analyzed. The main objective of this work is to find out the influence of combination herbal extract proportion, type of material and their interactive effect on the antibacterial properties. The quantitative antibacterial test (AATCC 100) results of the combination herbal extracts-treated single jersey knitted fabrics show that the 50%WT: 50%HB proportion showed consistent bacterial reduction performance against both Staphylococcus aureus and Escherichia coli bacterial strains in all the materials as supported from the test results of phytochemical screening, Minimum Inhibitory Concentration, Fractional Inhibitory Concentration index for synergy, Antioxidant, Cytotoxicity and GC-MS analysis. In terms of material, lyocell and micro-denier polyester fabrics showed good results in 12 hr and 24 hr contact time against S. aureus. Against E. coli, cotton and micro-denier polyester showed good results in 12 hr and 24 hr contact time, respectively.
PDF
