Thermal stability of nanocrystalline electrodeposited nickel–iron


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During the serial production process of a microgearbox, nickel–iron coatings are electrodeposited onto copper discs using various current densities and are subsequently annealed in a vacuum furnace in the temperature range between 200 and 800 °C. The microstructure (grain size and lattice strain) is characterised via X-ray diffraction (XRD) measurements. Following electrodeposition, nanocrystalline microstructures result whose grain sizes range from 8 to 12 nm. The iron content of the investigated coatings amounts to 5.7, 8.8 and 17.7 wt.%. By means of an annealing treatment, a reduction in the lattice strain and subsequent grain growth are observed. The change of the microstructural parameters is shifted to higher temperatures in the case of increasing iron content. Light microscope and scanning electron microscope (SEM) images show the formation of precipitations at about 400 °C. The indentation hardness and the indentation modulus change considerably after annealing.