2001

The corrosion resistance of tool steels used for pressure die casting in molten aluminum environment was investigated. Steel AISI H13, steel for combustion valves and raging steel without coating, with TiAlN coating applied by PVD process and with a semi permanent coating named Protalcar were used for the study. The experiment was conducted under conditions of continuous contact between the die and molten alloy to simulate the corrosion behaviour. Corrosion resistance in static immersion was evaluated as a reduction of the external surface plunged in molten aluminum.

The sinterability of two different ceramic wastes coming from the hydrometallurgy processing of zinc ores was investigated in view of their low-cost reuse as porous building materials for heat and sound insulation. Their chemical composition, the phase and mass changes during heat treatment were firstly investigated for setting up the thermal cycle for their densification. The materials demonstrated to sinter to high final density without any sintering aid at temperatures close to 1300 °C.

The oxidation behaviour of a FeCrAl alloy with little rare earth content (Y = 0.01 wt.%) was investigated. Specimens of this alloy were submitted to long-term oxidation treatments (up to 30 days) at 900 and 1200 °C, under gaseous atmospheres containing 21, 10 and 2 vol.% of O2. The weight gain for unit area was measured vs. oxidation time. The alumina scale growth was found to occur, at least during the first days of treatment, according to Wagner's parabolic law. Afterwards, the layer rate growth decreases down to that expected on the basis of this law.

Titanium matrix composites reinforced with continuous fibres are candidate materials for high performance structural components in aerospace applications. The present work has been focussed on the use of a fabrication methodology of composite monotapes alternative to the well known fibre-foil techniques. The same fabrication procedure was also selected to produce composite preforms suitable for secondary consolidation processes, as those based upon diffusion bonding methods, in order to obtain multilayered composites.

Three kinds of turbine blades (made by casting Renè 77, Renè 80 and CMSX-4 nickel based alloys) were submitted to an above pack aluminizing treatment. The suitability of this surface coating for preventing high temperature oxidation and hot salt corrosion was investigated. Oxidation tests were performed in air at 1050°C for 500 and 1000 h; salt corrosion at 950°C was studied by using a NaCl+Na2SO4 mixture. The microstructure of aluminized blades before and after these tests was compared by X-ray diffraction, scanning electron microscopy and electron probe microanalysis.

Forging behaviour of 2124 aluminium alloy containing 26 vol.% of SiC particles (average size 3 μm) was investigated by means of room and elevated temperature tensile tests (range of temperature 20–350°C). The results obtained were utilized to define the forging parameters (deformation ratio 3.5:1, strain rate 0.14 s−1, sample temperature during the hot deformation process ranging from 440 to 340°C). Microstructure of as-fabricated and forged specimens was investigated.