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Streszczenie:
The paper investigated the effect of electrospark alloying (ESA) on the formation of wear-resistant molybdenum disulfide (MoS2) based coatings for use in face impulse seal (FIS) of pumping equipment operating under conditions of high temperatures, pressure, aggressive environments and radiation exposure. The coatings were obtained on samples of austenitic AISI 321 steel. Two sulfomolybdenation methods have been developed: the first method involves the preliminary application of a sulfur-containing paste before ESA processing with a molybdenum electrode; the second one involves applying the MoS₂ powder and subsequent ESA processing with a molybdenum electrode. The microstructure, microhardness, phase composition and tribological properties of the coatings have been investigated. It was established that the formed coating had a structure comprised of three layers. Those are a porous surface layer, a strengthened layer and a diffusion zone. The maximum microhardness reached 1127 HV at Wp = 3.4 J. The results of tribological tests according to the “ball-disk” scheme showed a decrease in the friction coefficient to 0.0078 on samples obtained by the first ESA method. The obtained results confirm the feasibility of using the ESA methods with the inclusion of molybdenum disulfide in order to increase the operational reliability and durability of FIS units under extreme operating conditions. The proposed technologies can be implemented in production of pumping equipment for nuclear, chemical and energy industries

Słowa kluczowe:
Electrospark alloying, Molybdenum disulfide, Face impulse seal, Tribotechnical coatings, AISI 321 steel

Streszczenie:
In article we present the results of studies of the local x-ray spectral analysis of coatings formed by the electrospark alloying (ESA) method at the discharge energy Wp = 0.13, 0.52 and 0.9 J by anodes from nickel and stainless steel X10CrNiTi18-10 on the cathode surface from X10CrNiTi18-10 steel. During ESA by stainless steel X10CrNiTi18-10 anode with an increase Wp in characteristic points and from the entire investigated surface of the coating, the quantitative elemental composition is not changed. The analysis of elements distribution over the depth of the formed layer is showed that when using the electrode tool from steel X10CrNiTi18-10 with an increase in Wp, there are a slight decrease in chromium and an increase in nickel and titanium in the surface layer. When steel X10CrNiTi18-10 is replaced by nickel with an increase in Wp, the concentration of nickel on the coating surface decreases from 95.38 to 89.04%. As the recession deepens from the coating surface, the concentration of nickel gradually decreases, respectively, at Wp = 0.13, 0.52 and 0.9 J from 96.29, 90.29 and 89.04% on the surface to 9.0, 10.30 and 9.9% at depth: 120, 165 and 240 μm. At the same time, the concentration of chromium, titanium and iron gradually increases.

Słowa kluczowe:
electrospark alloying, nickel, steel, x-ray spectral analysis, scan step, topography, spectrum

Streszczenie:
The paper analyzes the works devoted to solving problems affecting the bearing life of rolling bearings (RB) and to revealing reserves for its increase. There proposed a new technology for forming a protective coating on the shaft bearing journal or on the surface of a sleeve pressed thereon, which consists in the use of a combined technology comprising a process for stage-by-stage aluminizing by the method of electrospark alloying (A ESA ) followed by a process of ion nitriding (IN). Such a coating has a 100% continuity, the greatest thickness of the increased hardness zone of 300 µm, the surface microhardness of 7700 MPa, and the roughness (Ra) after non-abrasive ultrasonic finishing (NAUF) of 0.5 µm, The results of the X-ray microanalysis indicate that an increased content of aluminum is observed in the surface layer at the distance of up to 40 µm after the stage-by-stage AESA process. The research results have shown that in order to restore the shaft bearing journal neck surface layer hardness, which had been lost because of the repair work, the step-by-step AESA technology is more preferable. Thus, when removing the surface layer to a depth of 0.15 mm and subsequently carburizing by the method of electrospark alloying (C ESA ), the maximum microhardness of the surface layer is 7250 MPa, and the thickness of the zone of the increased hardness is 150 µm, At subsequently processing by the AESA method, these quality parameters of the surface layer are, respectively, 7350 MPa and 210 µm. The use of the NAUF method, both after C ESA and AESA processes, makes it possible to reduce the surface roughness up to Ra = 0.5 µm. To decrease the surface roughness of the RB housing seat, it is advisably to practice burnishing with a diamond tool (DB) after the A ESA process