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FRACTURE OF TUNGSTEN MATERIALS V. H. Marynin

UDC 620.197.16

We determine the durability of mono- and polycrystals and various types of coatings under the action of rigidly fixed abrasive particles, cavitation, and multienergy flows of deuterium ions. We study monocrystals whose characteristics and technology of growth are described in [1]. The required crystallographic orientation was realized by using a URS-70 device with an accuracy of ± 1°. We measured the fracture rates of the principal crystallographic planes {100}, {110}, and {111}. The samples of polycrystals were prepared in the form of disks 10–16 mm in diameter and 2.9 – 3.1 mm in thickness according to the technology of production of cermet tungsten. The total amount of admixtures was equal to ∼ 0.15 wt.%. The average grain size in the samples varied from 8 to 130 µm. The coatings were applied by using vacuum-arc and gas-phase technologies. The arc current was equal to 100 A, the negative potential formed on the base made of 1Kh18N10T steel to 50 V, its temperature to (1030 ± 20)°K, its thickness to 2 mm, and the thickness of the applied coating to 25 µm. The samples of gas-phase tungsten (CVD) coatings were applied to the surface of VK6 alloy heated to a temperature of (820 ± 20)°K according to the reaction WF6 + 3H2 = W + 6HF. The WF6 content of a gas mixture was & 35 mol.%. The thickness of the coating was ∼ 1400 µm. The data of X-ray diffraction analysis reveals a texture whose [100]-axis is oriented in the direction perpendicular to the plane of growth of the coatings. The average grain size is ∼ 400 µm in the direction of growth and ∼ 25 µm in the perpendicular direction. We also studied tungsten produced according to the technology of hot pressing [2]. We used PWCh-type powders with the following mean grain-size composition: 40% of (0–1) µm, 35% of (1–2) µm, and 21% of (2–3) µm. The thickness of a layer of tungsten on a copper substrate was ∼ 1 mm. The average grain size was ∼ 1.5 µm. The microhardness measured in a transverse metallographic section under a load of 0.98 N was equal to 5.6 GPa. The intensity of wear was measured according to the weight losses of samples with an accuracy of ± 0.15 µg. The cavitation zone was formed in tap water by using an ultrasonic vibrator of exponential profile with an amplitude of oscillations of its surface of (30 ± 2) µm and a frequency of (21 ± 1.5) kHz. The distance between the end of the vibrator and the surface of the sample was equal to 0.5 mm. The samples were irradiated by a multienergy flow of deuterium ions in a DSM-2 magnetic trap with a magnetic field of mirror configuration. A plasma was created by the method of electron cyclotron resonance. The samples were placed at the outlet of plasma from the magnetic mirror and a negative potential varying from 0.1 to 1.5 kV was applied to these samples. The abrasive wear caused by abrasive particles rigidly fixed on a disk was studied by using the “disk– plane” scheme. The linear velocity of the disk near the surface of the sample was ∼ 3 m / sec, the loa