Combined Effect of a Laser Cladded Coating and Surface Texture on Tribological Performance Under Dry Sliding and Starved Lubrication

Fe-based alloy coating was laser cladded on gray cast iron using Ni-Cu alloy as an intermediate layer. The cross section of the laser cladded coating was characterized by optical microscopy (OM), scanning electron microscopy (SEM) equipped with energy dispersive spectrometry (EDS), X-ray diffraction (XRD), and a Vickers hardness tester. A microdimple texture was created by reciprocating an electrolyte jet with prefabricated mask (REJP) machining on an Fe-based alloy coating. The tribological performances of untextured and textured coatings were examined through interrupted wear tests using an in-house developed reciprocating ball-on-plate tribotester under dry sliding and starved lubricated conditions. The results show that the presence of microdimple edges in the nonconformal contact region has a detrimental effect on the friction performance under dry sliding. However, the microdimples can be beneficial for trapping debris to preserve a smoother contacting surface and thus a lower volume wear track compared to untextured coatings. Due to its role in oil reservoirs and debris entrapment, the microdimple textured coating can maintain a low friction coefficient for a long time period after lubricant oil cutoff and results in a lower volume wear track under starved lubrication. Graphical abstract

Preparation and Properties of Multilayer Ca/P Bio-Ceramic Coating by Laser Cladding

In order to enhance the bioactivity and wear resistance of titanium (Ti) and its alloy for use as an implant surface, a multilayer Ca/P (calcium/phosphorus) bio-ceramic coating on a Ti6Al4V alloy surface was designed and prepared by a laser cladding technique, using the mixture of hydroxyapatite (HA) powder and Ti powder as a cladding precursor. The main cladding process parameters were 400 W laser power, 3 mm/s scanning speed, 2 mm spot diameter and 30% lapping rate. When the Ca/P ceramic coating was immersed in simulated body fluid (SBF), ion exchange occurred between the coating and the immersion solution, and hydroxyapatite (HA) was induced and deposited on its surface, which indicated that the Ca/P bio-ceramic coating had good bioactivity. The volume wear of Ca/P ceramic coating was reduced by 43.2% compared with that of Ti6Al4V alloy by the pin-disc wear test, which indicated that the Ca/P bio-ceramic coating had better wear resistance.

Wear Resistance of Experimental Hard Alloys Grades with Co-Mo-Ti Binders upon Conditions of Friction without Lubricant on Stainless Steel

The results of studies of wear resistance and tribological properties of experimental single carbide hard alloys grades with modified Co-Mo-Ti binders upon conditions of friction without lubricant on stainless steel are presented. All the data obtained were compared with similar parameters for the basic alloy VK8 (Co-Mo), on the basis of which the experimental grades were developed. Tribological tests were performed on tribometer which implemented a scheme of friction "pin on disk" at constant sliding speed and normal load values with artificially heated tribo contact zone. Studies have found that partial substitution of cobalt in a binder by Mo and Ti has led to a decrease in average friction rates. It was established that the greatest wear resistance and the best tribological characteristics were obtained for specimens of experimental grade 2.22 (5,65%Co+1,8%Mo+0,6%Ti). The process of friction for this pin material was characterized by the formation of secondary structures with high shielding properties, reducing of the adhesive interaction of materials, low volume wear intensity, minimal friction coefficient, as well as the least roughness of friction tracks on the counter body (disk). An increase in the proportion of molybdenum in the binder of more than 5% reduced the wear resistance of the experimental grades in comparison with the basic alloy VK8.

Preparation and Tribological Properties of Modified MoS2/SiC/Epoxy Composites

In order to improve the tribological properties of epoxy (EP), EP composites were prepared by filling different proportions of silicon carbide (SiC) particles and molybdenum disulfide (MoS2) powder. SiC and MoS2 particle surfaces were modified by the silane coupling agent KH560 to improve dispersion and avoid agglomeration of the inorganic particles in the EP resin matrix. The effect of different proportions of modified MoS2 content on the tribological properties of SiC/EP composites, and the wear mechanism of the worn surface, were investigated when the filler content was fixed at 55 wt.%. The results indicate that the friction and wear properties of modified MoS2/SiC/EP composites are better than SiC/EP composites without modified MoS2. When the modified MoS2 content is 4 wt.%, the average friction coefficient and volume wear rate of the modified MoS2/SiC/EP composite are 0.447 and 14.39 × 10−5 mm3/N·m, respectively, which is reduced by 10.06% and 52.13% in comparison with that of the 55 wt.% SiC/EP composite. Furthermore, the average friction coefficient of a composite containing 4 wt.% MoS2 is 16.14% lower, and the volume wear rate is 92.84% lower than that of pure EP.

Enhanced tribological properties of bismaleimides with a novel hybrid silicon dioxide containing amino groups

To improve the tribological properties of bismaleimide (BMI) resin, silicon dioxide nanoparticles with imino and terminal functional amino groups were prepared through a sol–gel process to form a novel SiO2-NH2 hybrid. The as-prepared hybrid was then applied as a modifying agent for the BMI matrix to obtain SiO2-NH2/BMI composites. Compared to those of pure BMI resin, the volume wear rate and friction coefficient of the SiO2-NH2/BMI composites decreased significantly, while the wear mechanism changed from fatigue (BMI) to adhesive (SiO2-NH2/BMI) wear. This improvement in the tribological properties of the SiO2-NH2/BMI composites was attributed to the appropriate SiO2-NH2 added content, which endowed the BMI with excellent mechanical and thermal-resistant properties. Thus, the SiO2-NH2/BMI composites could resist the external load and excessive heat during the friction process.

Microstructure and Wear-Resistant Properties of Ni80Al20-MoS2 Composite Coating on Sled Track Slippers

In order to increase the surface hardness and wear-resistance property of sled track slippers, a Ni80Al20-MoS2 composite coating was fabricated on the surface of a stainless steel 0Cr18Ni9Ti sled track slipper via atmospheric spray and hot dipping. The microstructure, composition and surface hardness of coatings under different spraying powers were characterized and measured. The wear-resistant properties of the slipper substrate and the coating were also checked. The results showed that the higher the spraying power was, the greater the smoothness, density and hardness was of the Ni80Al20 coating, while the thickness initially increased and then decreased. When the spraying power was 18 kW, the thickness was 342.5 μm, the surface hardness was 304.1 Hv0.2, and the coating was composed of Ni, Al, Ni3Al, NiAl and a little Al2O3. The friction coefficient of the slipper substrate against GCr15 balls at room temperature in air was 0.7, while the coated substrate with MoS2 lubrication film was 0.3 and the volume wear rate declined by 1/5. The friction coefficient of the Ni80Al20 coating was 0.5 and the Ni80Al20-MoS2 composite coating was 0.15, while the volume wear rate declined by 1/4 and 1/3.

A Mixed Elasto-Hydrodynamic Lubrication Model for Wear Calculation in Artificial Hip Joints

The aim of this paper was to propose a novel in silico mixed elasto-hydrodynamic lubrication model with the purpose of wear prediction in Total Hip Replacements (THRs). The model considers the progressive wear contribution in the calculation of the meatus filled by the non-Newtonian synovial fluid. The results were referred to the gait cycle kinematics, calculated by using musculoskeletal multibody software, while the loading was assumed by literature in vivo measurements. The simulations allow evaluating the fluid and the contact pressure fields and the acetabular cup wear over the time. The results were obtained considering a Ultra High Molecular Weight PolyEthylene, UHMWPE, cup and were compared with results from the literature, showing a good agreement in terms of total volume wear of the cup.

New Insights of Wear Behavior Analysis on Low Temperature Treated AISI 253MA Stainless steel Material by Gas Nitriding Process

AISI 253MA Stainless steel samples were treat with the gas nitrating process at low heat around 450°C. It was seen that all-inclusive austenite stage exist when it is nitrade to 8 hours and post addition at time of nitrading to 16 hours the mix of ferrites and progressively substance of nitrogen was gathered in the following layers. Farther nitrading to 24 hour it has seen at Cr-N stage was discovered and turns the steel progressively firmer superficially. Erode tests were led by tribological wear testing machine to examine the tribological wear loss. Volume wear was found to be least in 18 hours test which demonstrated better improvement of wear improvement. High hardness were found in 24 hrs showing a hardness of 1080Hv. The sample nitrided to 24 hours exhibited better wear resistance, high hardness and low wear loss as well as low volume wear loss. Assessment examinations of nitrided test samples were investigated under scanning electron magnifying analysis.

THE EFFECT OF GRAPHENE ADDITIVE ON THE TRIBOLOGICAL PROPERTIES OF BIONIC LUBRICANT COMPOSITIONS TESTED BY THE SRV METHOD

The aim of the study was to investigate the effect of the addition of graphene dispersion on anti-wear properties of bionic lubricant compositions based on aqueous sodium hyaluronate solutions. Tribological tests were carried out using a SRV tester, enabling the tests to be carried out in conditions of linear oscillating movement of the bullet-shield type association in which the ball was made of aluminium oxide and the disc was made of bearing steel 100Cr6. For research, a 0.5% solution of sodium hyaluronate in water (composition BSS2) was chosen, which was the base to which the graphene additive was introduced. During the main stage of work, three lubricant compositions were tested, i.e., as well as BSS2 solution, into which 0.05% m/m or 0.1% m/m graphene oxide was introduced, respectively. The study allowed the observation of a clear anti-wear effect associated with the introduction of graphene preparations into the hyaluronan base, manifested in a change in the trend of the graph of the coefficient of friction over time. In addition, a reduction in the volume wear of friction node components was found. Based on the analysis of tribological research results, it was found that the anti-wear effect of the lubricant on the friction elements of the steel-ceramic material combination increases with increasing the content of the graphene preparation in the lubricant composition.

Tribological properties of aluminium alloy surface layer after finishing treatments

Investigation’s results of the surface geometric structure and tribological properties of the aluminum alloy EN AW-AlCu4MgSi(A) processed by various finishing treatments: grinding, polishing and ball burnishing are presented in the paper. The test of abrasive resistance and friction coefficient determination was carried out by usage of the T-01M tester. The tests were carried out under dry friction conditions using the ball-on-disc method. As a counter-sample, a polished Al2O3 ceramic ball with a diameter of 6 mm was used. After burnishing, comparing to grinding and polishing, an approximate twice reduction of the volume wear rate was obtained. Depending on the type of surface treatment mean friction coefficients are 0.45 after grinding, 0.34 after polishing and 0.32 after ball burnishing.