The surfaces of two engineering polymers including polyamide 66 (PA66) and polytetrafluoroethylene (PTFE) were treated by diffuse coplanar surface barrier discharges in atmospheric air. We found that plasma treatment improved the adhesion of PA66 for either polymer/polymer or polymer/steel joints, however, it was selective for the investigated adhesive agents. For PTFE the adhesion was unaltered for plasma treatment regardless the type of used adhesive. Tribological properties were slightly improved for PA66, too. Both the friction coefficient and wear decreased. Significant changes, again, could not be detected for PTFE. The occurred variation in the adhesion and tribology was discussed on the basis of the occurred changes in surface chemistry, wettability and topography of the polymer surface.

The aim of this work was to correlate the overall carbon content in NbC-Ni, NbC-Ni-VC and NbC-Ni-Mo starting powders with the resulting microstructure, hardness, and fracture toughness of Ni-bonded NbC cermets. A series of NbC-Ni, NbC-Ni-VC and NbC-Ni-Mo cermets with different carbon content were prepared by conventional liquid phase sintering for 1 h at 1420 °C in vacuum. Microstructural analysis of the fully densified cermets was performed by electron probe microanalysis (EPMA) to assess the effect of carbon and VC or Mo additions on the NbC grain growth and morphology. A decreased carbon content in the starting powder mixtures resulted in increased dissolution of Nb, V, and Mo in the Ni binder and a decreased C/Nb ratio in the NbC based carbide phase. The Vickers hardness (HV₃₀) and Palmqvist indentation toughness were found to decrease significantly with an increasing carbon content in the Mo-free cermets, whereas an antagonistic correlation between hardness and toughness was obtained as a function of the Mo-content in Mo-modified NbC cermets. To obtain optimized mechanical properties, methods to control the total carbon content of NbC-Ni mixtures were proposed and the prepared cermets were investigated in detail.

This current study proposed a new computationally efficient and comparatively accurate algorithm for calculating both static and dynamic coefficients of friction from high-frequency data. Its scope embraced an application in a real-time friction-based system, such as active braking safety systems in automobile industries. The signal sources were from a heavy-duty reciprocating dry sliding wear test platform, focused on experimental data related to friction induced by stick-slip phenomena. The test specimen was a polytetrafluoroethylene (PTFE)-coated basalt/vinyl ester composite material, tested at a large scale. The algorithm was primarily aimed to provide scalability for processing significantly large tribological data in a real-time. Besides a computational efficiency, the proposed method adopted to evaluate both static and dynamic coefficients of friction using the statistical approach exhibited a greater accuracy and reliability when compared with the extant models. The result showed that the proposed method reduced the computation time of processing and reduced the variation of the absolute values of both static and dynamic frictions. However, the variation of dynamic friction was later increased at a particular threshold, based on the test duration.

Roller conveyor chains are common used to transport goods in production lines or assemblylines, such as pallets, cars or steel coils. They are sometimes used in severe environments, soiled withwater, foreign particles, chemicals or other contaminants. Normal use will result in wear of the componentsof the chain which can lead to unexpected failure and costly production downtime. Today, few literature onthe wear of conveyor chain is available and there are almost no reliable test-rigs to generate and measurechain wear in a reproducible manner. In this research the different components of conveyor chains and theloading conditions are described. Additionally, the applications and (dis)advantages of chains with polymerrollers are discussed. The chain wear mechanisms found in literature are listed. Abrasive and adhesivewear between pin, bushing, roller and track are discussed. From the contact mechanics of the chain andpressure-velocity limit of the roller materials, the design constraints for the laboratory test-rig were derived.The capabilities and working principles of the developed test-rig are explained in this paper.

Polyamide (PA6/6) is often used as a tribological pair in abrasion prevalent applications such as hinges and sliders. PA6/6 is frequently processed by injection moulding and extrusion process. It is known that these processes influence the polymers mechanical behaviour, but their influence on the polymers wear response has not been studied. Hence the present research attempts to study the influence of different manufacturing processes on tribological behaviour for PA6/6. Wear tests were performed on a pin abrading tester (DIN 50322). Abrasion resistance of both extruded and injection moulded PA6/6 were tested at different loads (20 and 35 N). Single-pass (nonoverlapping mode) and multipass testing (overlapping mode) were used to understand the influence of clogging of wear debris. It is evidenced that with increasing load the specific wear rate decreases; moreover, fine abrasives tend to reduce the wear rate. In multipass testing a transfer layer clogged on the counterface that acted as a protective agent and lowers wear rate. Poor mechanical strength of injection moulded polymers is apparently compensated by microstructural response for having a similar wear behaviour between extruded and injection moulded PA 6/6. Hence a proper balance between microstructural and mechanical characteristics is an absolute must in PA 6/6 for better wear performance.