This work evaluates the dry sliding behavior of anodic aluminum oxides (AAO) formed during one traditional hard anodizing treatment (HA) and two golden hard anodizing treatments (named G and GP, respectively) on a EN AW-6060 aluminum alloy. Three different thicknesses of AAO layers were selected: 25, 50, and 100 μm. Prior to wear tests, microstructure and mechanical properties were determined by scanning electron microscopy (VPSEM/EDS), X-ray diffractometry, diffuse reflectance infrared Fourier transform (DRIFT-FTIR) spectroscopy, roughness, microhardness, and scratch tests. Wear tests were carried out by a pin-on-disc tribometer using a steel disc as the counterpart material. The friction coefficient was provided by the equipment. Anodized pins were weighed before and after tests to assess the wear rate. Worn surfaces were analyzed by VPSEM/EDS and DRITF-FTIR. Based on the results, the GP-treated surfaces with a thickness of 50 μm exhibit the lowest friction coefficients and wear rates. In any case, a tribofilm is observed on the wear tracks. During sliding, its detachment leads to delamination of the underlying anodic aluminum oxides and to abrasion of the aluminum substrate. Finally, the best tribological performance of G- and GP-treated surfaces may be related to the existence of a thin Ag-rich film at the coating/aluminum substrate interfaces.

Towards the end of the last century, vacuum heat treatment of high speed steels was increasingly used in the fabrication of precision cutting tools. This study investigates the influence of vacuum heat treatments at different pressures of quenching gas on the microstructure and mechanical properties of taps made of M35 high speed steel. Taps were characterized by optical microscopy, scanning electron microscopy with energy dispersive spectroscopy, X-ray diffraction, apparent grain size and Vickers hardness measurements, and scratch tests. Failure analysis after tapping tests was also performed to determine the main fracture mechanisms. For all taps, the results showed that microstructures and the values of characteristics of secondary carbides, retained austenite, apparent grain size and Vickers hardness were comparable to previously reported ones for vacuum heat treated high speed steels. For taps vacuum heat treated at six bar, the highest plane strain fracture toughness was due to a higher content of finer small secondary carbides. In contrast, the lowest plane strain fracture toughness of taps vacuum heat treated at eight bar may be due to an excessive amount of finer small secondary carbides, which may provide a preferential path for crack propagation. Finally, the predominant fracture mechanism of taps was quasi-cleavage.

This paper discusses the effect of different surface treatments on shape memory alloy wires embedded in PolyEster (PE) and VinylEster (VE) polymeric matrices. In particular, two types of chemical etching and a chemical bonding with a silane coupling agent have been performed on the surfaces of the wires. Pull-out tests have been carried out on samples made from a specifically designed Teflon mould. Considering the best results of the pull-out tests obtained with PE resin, the debonding induced by strain recovery of 4%, 5% and 6% pre-strained NiTi wires has been evaluated with the wires being subjected to different surface treatment conditions and then being embedded in the PE matrix. The results prove that the wires functionalised and embedded in the PE resin show the maximum pull-out forces and the highest interfacial adhesion. Finally, it has been found that debonding induced by strain recovery is strongly related to the propagation towards the radial direction of sharp cracks at the debonding region.