Institute of Fundamental Technological Research

In the article, as a result of comparative tests, it is established that steel samples with a coating applying the electrospark alloying method (ESA) with a BK6 hard-alloy electrode with the use of a special technological environment (STE) with a composition of 0.5%Si + 0.5%B + 2%Cr + 7%Ni + 90% vaseline, the wear of which after 24 hours of testing is of 221 mg that is 122% less than that for samples without coating and 15% and 31% for samples with coatings applying the nichrome-electrodes’ wire X20H80 using STE composition of 0.5%Si + 0.5%B + 59%BK6 + 40% vaseline and STE composition of 5%Si + 5%B + 90% vaseline, respectively, and by 22% and 47% less than with coatings applying the electrodes made by the method of powder metallurgy (PM), the composition of which is of 90%BK6 + 10%1M and 1M, respectively. For P6M5 steel, better resistance against hydroabrasive wear is possessed by samples with a coating applying the ESA method with an electrode made of hard alloy BK6 using STE composition of 0.5%Si + 0.5%B + 2%Cr + 7%Ni + 90% vaseline, the wear of which after 24 hours of testing is of 188 mg that is 43% less than in samples without coating and by 6% and 15% in samples with a coating applying the ESA method with an electrode made of nichrome wire of the composition X20H80 using STE composition of 0.5%Si + 0.5%B + 59%BK6 + 40% vaseline and STE composition of 5%Si + 5%B + 90% vaseline, and by 24% and 27% less than with coatings applying the electrodes produced by the PM method with a composition of 90%BK6 + 10%1M and 1M, respectively. In ESA with electrodes-tools made both by the PM method and by the new technology of wire X20H80 and hard alloy BK6 and STE, parts made of steel 45 and steel P6M5 have a decrease in the strength limit and yield limit, respectively, and both the relative elongation and the relative narrowing increase. With further abrasive-free ultrasonic finishing (AFUF), both the strength limit and the yield strength increase, and both the relative elongation and the relative narrowing decrease. For practical implementation, wear-resistant coatings formed according to the new technology, using tool electrodes made of X20H80 wire and hard alloy BK6 and STE in two stages with the following AFUF are proposed, the growth of the strength limit and the yield limit of which increase for steel 45 and steel P6M5 by 4.9% and 4.6% and 3.5% and 2.7%, respectively, and relative elongation and relative contraction decrease by 1.7% and 1.3% and 2.0% and 1.7%, respectively. At the same time, the surface roughness is Ra = 1.1 μm, and the integrity is of 100%

electrospark alloying, electrode tool, coating, white layer, microhardness, roughness, integrity

The article substantiates the importance and relevance of increasing problem of the performance and service life of babbitt sliding bearings (SB), which are the rotors supports of a large number of centrifugal pumps, compressors, turbines and other dynamic equipment operating at high operating parameters (speeds, loads and temperatures), as well as in conditions of corrosive, abrasive and other types of working environment’s influence. The analysis of the babbitt SBs production technology and operating conditions showed that the reason for the decrease in their durability are factors that are formed both at the stage of manufacture and during operation. SB failure under normal operating conditions is a consequence of wear various types: cavitation, abrasive wear, damage due to plastic deformations, fatigue damage, etc. The antifriction layer wear resistance depends on the mode of operation and design of the bearing, the physical properties of the connection between the layer and the base, the rigidity of the shaft and the bed under the bearings. As established, the bearing anti-friction layer quality must be evaluated according to the following criteria: adhesion strength of the coating to the base, cohesive strength of the anti-friction layer, porosity, and homogeneity of the structure. As established, during the production of SBs, the formation by the method of electrospark alloying (ESA) of a copper intermediate layer, firmly bonded with steel substrate, and tin layer (formation of solid substitution solutions) and babbitt provides a stronger (by 35%) of adhesion, compared to traditional technology (steel 20 + babbitt), steel substrate with babbitt, as well as more intensive removal of heat from the friction zone. As determined, a new technology in which all operations are carried out by the ESA method can be a reserve for improving the babbitt coatings formation quality, which significantly affects the durability of the SB. As determined, in order to determine a more rational technology for applying babbitt coatings, it is necessary to develop a physically based mathematical model that relates the wear of a certain amount of babbitt to the frictional work spent on it.

sliding bearing, babbitt, coating, wear, structure, transition layer, adhesion strength, electrospark alloying, mathematical model

In the article, a direct choice system of the most rational technology for applying a babbitt coating on the liners of sliding bearings (SB) is developed, which takes into account both economic and environmental requirements. On the basis of the performed research, a physically substantiated mathematical model of the babbitt-coatings’ wear process (wear equation) is proposed, which allows solving both the direct problem of determining weight and linear wears based on the known work of friction, as well as the inverse problem of finding the necessary work of friction to obtain the required amount of weight or linear wears. With knowing the time to reach a certain amount of wear, it becomes possible to operate the products more rationally, timely assigning the repair time and friction-surface catastrophic-wear preventing. In the course of research, a methodology is developed for determining the constants of the wear equation: activation energy (EA) as well as maximum weight (Δmб.п.н) and linear (Δhб.п.н) wears, which can be used as selection criteria for the most rational technology of applying a babbitt coating.

sliding bearing, babbitt, coating, wear, structure, transition layer, adhesion strength, electrospark alloying, mathematical model