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This paper presents the influence of plasma electrolytic oxidation parameters (peak current density, process time, pulse frequency) on the tribological properties and surface wettability of the produced coatings. The process parameters were selected in accordance with Hartley's research plan for three input variables with three variable values. Oxide coatings were made on the AZ31B magnesium alloy using a trapezoidal voltage waveform and a two-component alkaline electrolyte. The tribological properties of the coatings were determined as a result of tribological tests carried out on the T-17 tester in reciprocating motion. The tribological partner for the coatings was a PEEK/HPV pin. As a result of tribological tests, the friction coefficient µ, the mass wear of the pin and the average change in sample mass were determined. The tests showed changes in both the friction coefficient and pin wear. Before and after tribological tests, profilographometric measurements of the coatings were performed. The tests allowed for the determination of roughness parameters and the load–bearing curve of the sample surfaces. Surface wettability tests were carried out by determining the contact angles. [ABSTRACT FROM AUTHOR]

This paper presents the results of tribological tests on WE43 and WE54 magnesium alloys with rare earth metals performed in linear reciprocating motion for four different material couples (AISI 316-L steel, silicon nitride—Si3N4, WC tungsten carbide, and zirconium dioxide—ZrO2). Additionally, magnesium alloys were subjected to a complex heat treatment consisting of precipitation hardening combined with a deep cryogenic treatment. The study presents the effect of deep cryogenic treatment combined with precipitation hardening on the tribological properties of WE43 and WE54 alloys. Tribological tests revealed the most advantageous results for the magnesium alloy—AISI 316-L steel friction node. For both alloys tested after heat treatment, a nearly 2-fold reduction in specific wear rate has been achieved. Furthermore, microscopic examinations of the wear track areas and wear products were performed, and the wear mechanisms and types of wear products occurring in linear reciprocating friction were determined. Wear measurements were taken using the 3D profilometric method and compared with the results obtained from calculations performed in accordance with ASTM G133 and ASTM D7755, which were modified to improve the accuracy of the calculation results (the number of measured profiles was increased from four to eight). Appropriately selected calculation methods allow for obtaining reliable tribological test results and enabling the verification of both the most advantageous heat treatment variant and material couple, which results in an increase in the durability of the tested alloys. [ABSTRACT FROM AUTHOR]

The article presents the effect of anodizing parameters of the EN AW-5251 aluminum alloy on the thickness and roughness of Al2O3 layers as well as their wettability and tribological properties in a sliding combination with the T7W material. The input variables were the current density of 1, 2, 3 A/dm2 and the electrolyte temperature of 283, 293, 303 K. The tribological tests were performed on the T-17 tester in reciprocating motion, in conditions of technically dry friction. The tests were carried out on a 15 km road with a constant average slip speed of 0.2 m/s and a constant unit pressure of 1 MPa. The measurement of the wettability of the layers was performed using the sitting drop method, determining the contact angles on the basis of which the surface free energy was calculated. The profilographometric measurements were made. The analysis of the test results showed that the anodizing parameters significantly affect the thickness of the Al2O3 layers. The performed correlation analysis also showed a significant relationship between the roughness parameters and the wettability of the surface of the layers, which affects the ability to create and maintain a sliding film, which in turn translates into sliding resistance and wear of the T7W material. The analysis of friction and wear tests showed that the layer with hydrophobic properties produced at a current density of 1 A/dm2 in an electrolyte at a temperature of 283 K is the most favorable for sliding associations with T7W material. [ABSTRACT FROM AUTHOR]

The mechanical and tribological characteristics of the Ti-6Al-7Nb alloy were investigated within a wide range of temperature and time parameters of thermal oxidation. The hardness, HIT, and indentation modulus, EIT, of the alloy in question, with and without an anti-wear oxide layer, were determined. The tribological properties of sliding couples were studied under technically dry friction conditions, using a ball-on-disc tribometer. The test pieces were non-oxidized and oxidized Ti-6Al-7Nb alloy discs, and Al2O3, ZrO2, and 100Cr6 balls were used as counter specimens. After thermal oxidation, the surface of the titanium alloy was characterized by a significantly higher hardness, HIT (8–10 GPa), compared to the surface not covered with oxide layers (3.6 GPa). The study showed that the curvature of the loading segments increased with an increasing oxidation temperature, indicating a strong positive dependence of hardness on the thermal oxidation temperature. The value of the indentation modulus, EIT, was also found to increase with the increasing oxidation temperature. The intensity of the tribological processes was strictly dependent on the oxidation parameters and the couple's material (Al2O3, ZrO2, 100Cr6). It has been shown that the thermal oxidation process makes it possible to control, within a wide range, the friction-wear characteristics of the Ti-6Al-7Nb alloy. [ABSTRACT FROM AUTHOR]

The article presents the results of an aluminum oxide layer doped with monolayer 2H tungsten disulphide (Al2O3/WS2) for applications in oil-free kinematic systems. The results concern the test carried out on the pneumatic actuator operational test stand, which is the actual pneumatic system with electromagnetic control. The cylinders of actuators are made of Ø 40 mm aluminum tube of EN-AW-6063 aluminum alloy which is used in the manufacture of commercial air cylinder actuators. The inner surfaces of the cylinder surfaces were covered with an Al2O3/WS2 oxide layer obtained by anodic oxidation in a three-component electrolyte and in the same electrolyte with the addition of tungsten disulfide 2H-WS2. The layers of Al2O3 and Al2O3/WS2 obtained on the inner surface of the pneumatic actuators were combined with a piston ring made of polytetrafluoroethylene with carbon (T5W) material and piston seals made of polyurethane (PU). The cooperation occurred in the conditions of technically dry friction. After the test was carried out, the scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS) analysis of the surface of the cylinder bearing surfaces and piston seals of the pneumatic cylinders was performed. The analysis revealed the formation of a sliding film on the cylinder surface modified with tungsten disulfide, as well as on the surface of wiper seals. Based on the SEM/EDSM tests, it was also found that the modification of the Al2O3 layer with tungsten disulfide contributed to the formation of a sliding film with the presence of WS2 lubricant, which translated into smooth cylinder operation during 180 h of actuator operation. The cylinder with the unmodified layer showed irregular operation after approximately 70 h thereof. [ABSTRACT FROM AUTHOR]

This study investigated the micromechanical and tribological properties of WE43 alloy (Mg-Y-Nd-Zr) alloy subjected to cryogenic treatment and precipitation hardening. Microindentation tests were carried out in the range of load from 100 to 1000 mN. The introduction of deep cryogenic treatment (DCT) was shown to increase hardness and Young's modulus, and reduce the total indentation work. As the load set during the tests increased, a gradual decrease in the measured values was observed, indicating a significant relationship between the indent size and the value of the measured parameters. Cryogenic treatment used in conjunction with precipitation hardening (after solutioning and after aging) reduces the tribological wear of the alloy. Tests have shown an almost twofold reduction in the area of the wear trace and in the volumetric wear of the alloy, as well as a more than twofold reduction in linear wear, with relatively small fluctuations in the coefficient of friction. Abrasion was the main mechanism of wear. Areas where microcutting, adhesion and plastic deformation occurred were also observed. The results indicate the significant effectiveness of the applied heat treatment in improving the service life of the WE43 alloy containing rare earth metals. [ABSTRACT FROM AUTHOR]

Titanium and its alloys are among the most promising biomaterials for medical applications. In this work, the isothermal oxidation of Ti-6Al-7Nb biomedical alloy towards improving its mechanical properties, corrosion resistance, and bioactivity has been developed. The oxide layers were formed at 600, 700, and 800 °C for 72 h. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), 3D profilometry, and microindentation test, were used to characterize microstructure, surface geometrical structure, and the hardness of the diphase (α + β) Ti-6Al-7Nb alloy after oxidation, respectively. In vitro corrosion resistance tests were carried out in a saline solution at 37 °C using the open-circuit potential method and potentiodynamic measurements. Electronic properties in the air were studied using the Scanning Kelvin Probe (SKP) technique. The bioactivity test was conducted by soaking the alkali- and heat-treated samples in simulated body fluid for 7 days. The presence of apatite was confirmed using SEM/EDS and Fourier Transform Infrared Spectroscopy (FTIR) studies. The thickness of oxide layers formed increased with the temperature growth from 0.25 to 5.48 µm. It was found that with increasing isothermal oxidation temperature, the surface roughness, hardness, corrosion resistance, and contact potential difference increased. The Ti-6Al-7Nb alloy after oxidation revealed the HAp-forming ability in a biological environment. [ABSTRACT FROM AUTHOR]

The paper investigates changes in the structure, microhardness, and sclerometrical and tribological properties of a Mg-Y-Nd alloy under the influence of deep cryogenic treatment (DCT) in combination with heat treatment. The solution treatment was carried out at 545 °C for 8 h, aging was carried out at 250 °C for 24 h, and the deep cryogenic treatment applied at different treatment stages was performed at −196 °C. Tests showed a significant increase in the number of β-phase precipitates identified as Mg46.1Y6.25RE3.45 in the alloy subjected to DCT after solution treatment followed by aging. In addition, an approximately 20% reduction of the grain size was observed. Changes in the structure in the precipitation process strengthened the alloy and resulted in an increase of its hardness. At the same time, sclerometric tests allowed the micromechanism of wear and the coefficient of resistance to abrasive wear to be determined. Tribological tests showed a three-fold reduction in the volumetric wear and a considerable reduction of the friction coefficient, with the main mechanism observed during friction being abrasive wear. The most favorable properties of the alloy were obtained after precipitation hardening combined with DCT, resulting in a large increase in resistance to abrasive wear. Additionally, the formation of deep scratches in the examined material was reduced. The introduction of sub-zero treatment reduces the precipitation hardening time, and the results obtained indicate that the service life of the Mg-Y-Nd alloy can be extended. [ABSTRACT FROM AUTHOR]

This research investigated the effect of irradiation with an electron beam energy of 10 MeV in doses of 26–156 kGy on polytetrafluoroethylene (PTFE) with a 15% and 20% graphite additive. The research has shown that mechanical (compression strength, hardness, and Young's modulus) and sclerometric (coefficient of wear micromechanism and coefficient of resistance to wear) properties improve and tribological wear decreases as graphite content increases. Electron beam irradiation increases the degree of crystallinity of both materials to a similar extent. However significant differences in the improvement of all examined properties have been demonstrated for PTFE with higher (20%) graphite content subjected to the electron beam irradiation. This polymer is characterized by higher hardness and Young's modulus, reduced susceptibility to permanent deformation, higher elasticity, compression strength, and above all, a nearly 30% reduction in tribological wear compared to PTFE with a 15% graphite additive. The most advantageous properties can be obtained for both of the examined composites after absorbing a dose of 104 kGy. The obtained results hold promise for the improvement of the operational life of friction couples which do not require lubrication, used for example in air compressors and engines, and for the possibility of application of these modified polymers. In particular PTFE with 20% graphite content, in the nuclear and space industry. [ABSTRACT FROM AUTHOR]

This study analyzed the effects of irradiation of polytetrafluoroethylene (PTFE) containing 40% of bronze using an electron beam with energy of 10 MeV. Dosages from 26 to156 kGy (2.6–15.6 Mrad) were used. The impact of a high-energy electron beam on the thermal, spectrophotometric, mechanical, and tribological properties was determined, and the results were compared with those obtained for pure PTFE. Thermal properties studies showed that such irradiation caused changes in melting temperature Tm and crystallization temperature Tc, an increase in crystallization heat ∆Hc, and a large increase in crystallinity χc proportional to the absorbed dose for both polymers. The addition of bronze decreased the degree of crystallinity of PTFE by twofold. Infrared spectroscopy (FTIR) studies confirmed that the main phenomenon associated with electron beam irradiation was the photodegradation of the polymer chains for both PTFE containing bronze and pure PTFE. This had a direct effect on the increase in the degree of crystallinity observed in DSC studies. The use of a bronze additive could lead to energy dissipation over the additive particles. An increase in hardness H and Young's modulus E was also observed. The addition of bronze and the irradiation with an electron beam improved of the operational properties of PTFE. [ABSTRACT FROM AUTHOR]