Study of the Mechanical Behaviour of Al-Cu-Fe Quasicrystalline Coatings Across a Broad Range of Temperatures

The mechanical behavior of Al63Cu25Fe12 quasicrystalline coatings in the temperature range of 77-1073 K was studied by the microindentation method. Coatings with a thickness of 350 mu m were obtained on the substrate of steel 45 by high-speed air-fuel spraying of water-atomized powders with a size fraction of 40-80 mu m. The content of the icosahedral quasicrystalline phase in the coatings after production was 75 wt.%. Annealing at 998 K for 20 min made it possible to obtain 100% of the quasicrystalline phase in the coating. The microhardness of the studied coatings at a temperature of 77 K and room temperature (293 K) is similar to 7 GPa and slightly decreases to a level of similar to 4.5 GPa at a temperature of 725 K, followed by a sharp decrease to 1.5-1 GPa at 923-973 K. Analysis of the temperature dependence of the plasticity characteristic delta(H), determined by the indentation method, showed that up to a temperature of 873 K, the quasicrystalline coatings of the Al-Cu-Fe system have the brittleness during compression/tension tests, and above 873 K they start to possess a macroplasticity. Calculation of the value of delta(H) in a wide temperature range makes it possible to predict the mechanical properties of brittle, at standard test methods, quasicrystalline coatings of the Al-Cu-Fe system.