The Royalloy steel was boronized at 1173, 1223, 1248, 1273 or 1323 K for 1, 3, 5, 7 or 10 h using a Durborid powder mixture. The boronized samples were analyzed by scanning electron microscopy, X-ray diffraction and Vickers microhardness testing. The kinetic activity of boronized layers growth obeys the parabolic law, and the maximum thickness was 182 ± 10 µm. The thickness of FeB makes up to 40% of the total layer thickness. The obtained layers have two phases, which were composed of FeB and Fe2B phases, except for the sample boronized at 1173 K for 1 h which had an Fe2B layer only. The microhardness of the Fe2B phase had a range of 1370–1703 HV0.1, and that of the FeB phase was within 1727–2231 HV0.1. During the boronizing process, the chromium created extra particles with the highest amount of chromium in the transient region. The highest amount of silicon was observed at the boride layer/substrate interface. The amount of manganese was slightly lower in the boride layers compared to the amount in the substrate. Finally, the integral diffusion model was applied to determine the boron activation energies in the FeB and Fe2B layers, and this was followed by a comparison with the literature data.

In this work, plain, low carbon steel S235JRG1 was boronized at 1273 K for 45-150 min by using a Durborid powder. The microstructure, phase constitution and oxidation behavior of the resulting boride layers have been investigated. Layers with an average thickness of 76-123 µm have been produced. The boride layer has a distinct tooth-like microstructure. It is composed of Fe2B and FeB in unequal amounts. The boride layer oxidation behavior has been investigated by a simultaneous thermal analysis in a flowing synthetic air at 873-1173 K for 21-24 h. A parabolic oxidation of the boride layer has been observed. The rate constants are found between 1.039 × 10 −9 to 3.781 × 10 −6 kg 2 m −4 s −1 , depending on temperature and oxidation time. The activation energy of oxidation at temperatures below 1173 K has been estimated to be 93 kJ mol −1 . At 1173 K, two successive parabolic periods have been found, followed by a breakaway oxidation behavior. The oxide scale of the boronized steel is composed of different iron oxides and iron borates. The oxidation mechanisms of boride coatings are discussed and implications towards high temperature stability are provided.K e y w o r d s : boronizing, high temperature oxidation, X-ray diffraction, thermogravimetric analysis

The fabrication of polylactic acid (PLA)-carbonated hydroxyapatite (cHAP) composite material from synthesised phase pure nano-cHAP and melted PLA by mechanical mixing at 220-235 °C has been developed in this study. Topographical structuring of PLA-cHAP composite surfaces was performed by direct laser writing (DLW). Microstructured surfaces and the apatite distribution within the composite and formed grooves were evaluated by optical and scanning electron microscopies. The influence of the dopant concentration as well as the laser power and translation velocity on the composite surface morphology is discussed. The synthesis of carbonated hydroxyapatite (cHAP) nanocrystalline powders via wet chemistry approach from calcium acetate and diammonium hydrogen phosphate precursors together with crosslinking and complexing agents of polyethylene glycol, poly(vinyl alcohol) and triethanolamine is also reported.Thermal decomposition of the gels and formation of nanocrystalline cHAP were evaluated by thermal analysis, mass spectrometry and dilatometry measurements. The effect of organic additives on the formation and morphological features of cHAP was investigated. The phase purity and crystallinity of the carbonated apatite powders were evaluated by X-ray diffraction analysis and FT-IR spectroscopy.2

In this work, the high temperature oxidation behavior of Al71Co29 and Al76Co24 alloys (concentration in at.%) is presented. The alloys were prepared by controlled arc-melting of Co and Al granules in high purity argon. The as-solidified alloys were found to consist of several different phases, including structurally complex m-Al13Co4 and Z-Al3Co phases. The high temperature oxidation behavior of the alloys was studied by simultaneous thermal analysis in flowing synthetic air at 773–1173 K. A protective Al2O3 scale was formed on the sample surface. A parabolic rate law was observed. The rate constants of the alloys have been found between 1.63 × 10−14 and 8.83 × 10−12 g cm−4 s−1. The experimental activation energies of oxidation are 90 and 123 kJ mol−1 for the Al71Co29 and Al76Co24 alloys, respectively. The oxidation mechanism of the Al-Co alloys is discussed and implications towards practical applications of these alloys at high temperatures are provided.

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