Electric-spark alloying of VT22 alloy by chromium and tungsten electrode materials
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ELECTRIC-SPARK ALLOYING OF VT22 ALLOY BY CHROMIUM AND TUNGSTEN ELECTRODE MATERIALS О. V. Paustovs’kyi,1 V. І. Novikova,1 І. І. Tymofeeva,1 О. H. Molyar,2 Yu. V. Hubin,1 N. М. Mordovets’,1 L. P. Isaeva,1 and А. D. Kostenko1 We investigate the dependence of the erosion characteristics of Cr and W electrode materials during deposition of an electric-spark coating on VТ22 titanium alloy. The interrelation between the phase composition, structure, and tribological properties of a coating obtained by electric-spark alloying is determined. It is shown that a coating obtained from tungsten has optimal tribological properties: a microhardness of 16 GPa and a wear resistance of 4.9 μm/km at a sliding velocity of 5 m/sec and a load of 0.5 MPa. Keywords: electric-spark alloying, high-strength titanium alloy, structure, tribological properties.
In the modern engineering and aircraft industry, titanium alloys, especially VT22 high-strength alloy, are extensively used. They have increased chemical activity and susceptibility to galling with metals, due to which they exhibit low wear resistance. For this reason, VТ22 alloy is used only with modified surfaces [1]. One of the methods of deposition of protective coatings on its surface is electric-spark alloying (ESA), the main feature of which consists of obtaining an alloyed layer firmly adhering to the substrate. Equipment for ESA is simple and structurally convenient. This method is promising and uses electric pulses of small duration and a high current strength [2–5]. In what follows, we investigate the structure and properties of ESA coatings with Cr and W on VТ22 alloy. Alloying was performed in an ЕFІ-46А sputtering unit in the following mode: I = 1.5 А and C = 300 μF. The tribological characteristics of the compositions were assessed on an М-22М unit [6], which recorded the friction coefficient (f) and wear rate of a specimen ( I , μm/km) by the insert–shaft scheme. The tribological indices were determined in air without feeding lubricant in the contact zone in pair with 65H steel at V = 5 and 10 m/sec under a load of P = 0.5 and 1.0 MPa. We performed a metallographic analysis with a МIМ-9 microscope, a durometric analysis with PMT-3, and an X-ray phase analysis with DRON-3M in CuK α radiation. We investigated the influence of the phase composition of the anode on the main parameters of ESA of the alloy, namely, the specific erosion of the anode Δ a and the specific increment in the weight of the cathode
Δ c , which were measured for each minute of treatment per 1 cm 2 of the surface, the total erosion of the anode ΣΔ a and the total increment in the weight of the cathode ΣΔ c , which were measured for an alloying time of 1
Frantsevych Institute for Problems of Materials Science, Ukrainian National Academy of Sciences, Kyiv, Ukraine. Kurdyumov Institute for Metal Physics, Ukrainian National Academy of Sciences, Kyiv, Ukraine; e-mail: [email protected] (corresponding author). 2
Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 47, No. 1, pp.
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