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In this study, the influence of heat treatments up to 1200°C in vacuum on coatings prepared by atmospheric plasma spraying (APS) from a blend of 25 mol% Al2O3, 25 mol% Cr2O3 and 50 mol% TiO2 on microstructure, porosity, hardness and sliding wear resistance was investigated. The well-known transformation from α-Al2O3 to γ-Al2O3 occurred as a result of the spray process, as well as small amounts of titanium were found in Cr2O3 splats due to an interaction between the feedstock particles. No significant changes were found after a heat treatment at 400°C or 800°C. Heat treatment at 1200 °C led to complete coating delamination. Besides the retransformation of γ-Al2O3 to α-Al2O3, interactions between Cr2O3 and TiO2 splats and the formation of CrTi2O5 was observed. The formation of Al2Ti7O15 was observed in result of a reaction at the outer regions of the Al2O3 splats. At the same time, a reduction in porosity and healing of microcracks were observed as a result of sintering processes, which leads to an increase of the coating hardness to 1170 HV0.2.

Organo-functional silane coupling agents are widely used to promote adhesion in between inorganic and organic materials. Amino-functional silanes can improve bonding with polyamide. Aiming on a mechanically performant aluminum-polyamide joints, the effect of six amino silanes of different chemical structure, namely number and type of amine groups and alkyl spacers lengths, on the joint strength is investigated by means of lap-shear testing. Higher shear strengths are found along with a more pronounced capability of the amine group to form hydrogen bonds with polyamide. The results show that an additional amine group within the organo-functional group can increase joint strength, whereas long alkyl spacers reduce the observed joint strength. It is shown that high lap-shear strengths, in maximum about 15 MPa for N-(2-aminoethyl)-3-aminopropyltrimethoxysilane are achieved and that the high reproducibility can be assured when using right processing routines.

In order to achieve the desired properties, the microstructure of metals is often modified by heat treatments. A suitable combination of high strength and good ductility can be achieved by adjusting the amounts of martensite and retained austenite through a Quenching and Partitioning (Q&P) process. Controlling these material properties offers new potentials in the production of light weight steel parts. This paper presents a basic study of heat treatment conditions with subsequent microstructural characterization of quenched and partitioned commercial 0.54C-1.45Si-0.71Mn spring steel. Beginning from full austenitization, different quenching and partitioning parameters were applied. Microstructural characterization was performed using optical microscopy in combination with different etching methods as well as Scanning Electron Microscopy (SEM) and Electron Backscattered Diffraction (EBSD). It is shown that the intended dual phase microstructure with a specific phase fraction of austenite can be produced. Those results and consideration of hardness measurements show that the investigated commercial spring steel is a promising candidate for improving mechanical properties by a Q&P process.