PSI - Issue 32

M.A. Eryomina et al. / Procedia Structural Integrity 32 (2021) 284–290 Eremina/ StructuralIntegrity Procedia 00 (2019) 000 – 000

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1. Introduction High hardness (up to 17 GPa) and wear resistance of η -carbides (Fe,W) 6 C and (Fe,W) 12 C make it possible to use them as a hardening additive in the production of high-speed steels and alloys, and electrode materials. The carbides of these stoichiometries are mainly obtained using high- temperature (above 1000°C) remelting of the initial ingredients. Mechanical alloying of tungsten, iron, and graphite powders allows one to reduce the temperature of the η -carbide formation down to 700 –1000°C and to obtain powders with micron-sized particles in nanostructured state as it shown by Matteazzi et al. (1991), Wang et al. (1996), Tsuchida et al. (2001), Barona Mercado et al. (2007), and Zhang et al. (2017). The most effective and facile way of producing (Fe,W) 6 C and (Fe,W) 12 C carbides has been previously shown to be mechanical alloying of tungsten and iron powders in liquid hydrocarbon followed by annealing at 900°C (see Eryomina et al. (2020)). The as-synthesized carbide powders can be compacted and sintered to form parts of mechanisms, and also applied to the surface of various products as hard and wear-resistant coatings. The work is focused on the phase composition and wear resistance of compacts and coatings based on (Fe,W) 6 C and (Fe,W) 12 C carbides mechanosynthesized in a liquid hydrocarbon. 2. Experimental details The powders of W and Fe were mechanically alloyed in petroleum ether for 6 h in a planetary ball mill Fritsch P 7. The vials and balls are made of ShKh15 steel (C - 1, Cr - 1.5 wt%). The W:Fe mass ratios were 80:20 (Sample 1), 74:26 (Sample 2), 72:28 (Sample 3) and 70:30 (Sample 4). The milled powders were compacted by magnetic-pulse compacting at 500°C followed by annealing at 900°C for 1 h in argon (see Eryomina et al. (2020)). The coatings were formed on Armco iron plates using selective laser sintering with a Nd:YAG laser (  μ m, average power of 50 W, frequency100 kHz, pulse duration 100 μ s) in argon (seeKharanzhevskiy et al. (2014) and Kostenkov et al. (2012)). Thescanningspeedwasof 100 mm/s. The spot size at focus point was of 30  m. The structural-phase state of the samples was analyzed on a MiniFlex diffractometer (Rigaku Corp.) with the Co K α radiation over the 2  range of 1 0° to 140°. The microstructure of comp acts was studied using a VEGA 3 LMN scanning electron microscope and MIM 8M optical microscope. The density of compacts was measured by hydrostatic weighing. The Vickers microhardness was evaluated with PMT-3 at a load of 0.98 N, with ten measurement tests being conducted for each specimen for 10 s. Tribological tests were performed in three different ways. First, the abrasive wear resistance of samples was analyzed on a three-axis CNC milling machine PROFI "KKhZA" (PROFI, Germany).

Fig. 1. XRD patterns for compacts of (1) Sample 1 and (2) Sample 4.

Fig. 2.SEM image of compact for Sample 4.