The Avinit duplex technology has been developed by means of plasma precision nitriding of Avinit N and the subsequent application of a multifunctional antifriction coating Avinit C on the surfaces of rubbing bodies and perceives power loads. The influence of the duplex process on the dimensions of the parts was investigated; the properties of the nitrided layer and the parameters of Avinit coatings were studied. Avinit duplex technology ensures the application of highly adherent, high-quality multifunctional anti-friction wear-resistant Avinit C coatings on complex-profile parts. Using the developed Avinit duplex technology, a pilot batch of separators for the freewheel of the main gearbox of the helicopter was manufactured. All parameters of the separator, manufactured using the Avinit duplex technology, fully comply with the technical, metallurgical and metallographic requirements of design documentation (thickness and microstructure of the nitrided layer, no brittleness, thickness and hardness of the coating, preservation of geometric parameters with an accuracy of 0.5 microns). The Avinit coated freewheel separator has been successfully tested as part of the main gearbox for a helicopter at a full-scale stand. As shown by the test results, the use of the developed Avinit duplex technology ensures the complete absence of fretting wear of the working surfaces, which is common for serial separators.
The effect of nitriding of VT5 alloy (3.7115) in the plasma of a glow discharge excited in a hollow cathode on its tribological characteristics in pairs with different materials in jet fuel TS-1 and under dry sliding conditions has been studied. For research and tribological tests, samples of VT5 alloy were nitrided in the plasma of a glow discharge excited in a hollow cathode at a temperature of 975 ± 15 °C and a pressure of 58 ± 2 Pa in a nitrogen-argon gas mixture with a nitrogen content of 78 vol. %. Tribological tests were performed on a friction machine 2070 SMT-1 according to the scheme "cube-roller". Tests under conditions of sliding with jet fuel TS-1 were performed at a load of 200 N. The sliding speed during the tests was 1.3 m/s, and the test time was 75 s. The test under dry sliding conditions was carried out at a load of 100 N and a sliding speed of 0.785 m/s. The test time was 30 minutes. It is shown that the nitrided VT5 alloy in friction pairs with several materials has rather low wear values (≤ 2.26 × 10–6 mm3/Nm), as well as a coefficient of friction at the level of 0.08 to 0.12.
This paper reports comparative tribotechnical tests of surfaces, hardened by cementation and plasma nitridingAvinit N, for contact fatigue strength at friction in rolling with slipping. Following the cementation, the samples' hardened layer thickness was 1.2 mm; on nitriding, the thickness of the hardened layer was 0.25 mm. The tests were carried out using an acoustic emission method, which is extremely sensitive when registering the transition of tribosystems' operation from the normal (mechanochemical) wear to the initial surface destruction of a fatigue nature. The tests have shown that the average number of cycles before the initial destruction due to fatigue for the samples hardened by the Avinit nitriding technology is 1.82-time higher compared to the cementation-hardened samples. The depth of damage at the surface of the cemented samples could vary between 0.01 and 0.027 mm depending on the diameter of the damage. For the nitrided surfaces, the depth of damage did not exceed 0.003 mm. The samples' resistance to the fatigue wear (destruction) was determined by tests based on 1,000,000 cycles at contact loads σ max =1,140 MPa, typical of medium-loaded surfaces. The test results demonstrated that the integrated multicyclic resistance to fatigue wear (destruction) of the samples, hardened by nitriding, is more than 10 times higher than that of the cementation-hardened samples.The study reported here confirms the effectiveness of using the Avinit ion-plasma nitriding technology instead of cementing, to improve the contact strength of the parts' surfaces. At the same time, worth noting are the advantages of this technology to maintain the size and high quality of surface treatment, which eliminates the need to mechanically finish them after hardening
One of the modern methods of improving operating characteristics of titanium and titanium-based alloys under conditions of friction and increased contact loads is the method of ion-plasma nitriding. The effect of nitriding of VT5 alloy (Al 4,5-6,7 %, V to 1,2 %, Mo to 0,8 % − analogue 3.7115) in the plasma of a glow discharge excited in a hollow cathode on its tribological characteristics in pairs with different materials in T-1 fuel and under dry friction conditions has been studied. For research and tribological tests, samples of VT5 alloy were nitrided in the plasma of a glow discharge excited in a hollow cathode at a temperature of 975 ± 15°C and a pressure of 58 ± 2 PA in a nitrogen-argon gas mixture with a nitrogen content of 78 %. Studies of samples of VT5 alloy after nitriding showed that the surface roughness Ra was in the range of 0.58-0.64, and the surface hardness HV5 was 525 ± 20 kgf/mm² at a base hardness of 325 ± 15 kgf/mm². Tribological tests were performed on a friction machine 2070 SMT-1 according to the scheme "cube - roller". Tests under conditions of friction with oil were performed at a load of 200 N. The sliding speed during the tests was 1.3 m/s, the test time was 75 sec. The test under dry friction conditions was carried out at a load of 100 N and a sliding speed of 0.785 m/s, the test time was 30 minutes. Low wear ability in relation to the nitrided titanium alloy VT5 (<2.4x10-4 mm3/s), as well as friction coefficients at the level of 0.08 to 0.12 in the order of their growth had bronze VB-23NTS (Pd 18–22 %, Ni 3–4 %, Zn 3–4 %, Sb 3–4 %, P 0.15–0.3) r.O10C2N3, VB-24 (Sb 4.7–6, 2 %, P 0.4–0.9), steel 1.3505, cast iron GGG80, cemented steel 20Cr3MoWV
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