Technological Parameters of Production and Properties of Babbit-Based Composite Surfacing Rods and Deposited Antifriction Coatings

Abstract

A method for production of Sn–Sb–Cu alloy (babbitt) based composite coatings reinforced with micron-sized SiC and B4C particles on a steel substrate has been developed. A combined action of uniformly distributed high-modulus reinforcements and plastic matrix increases the strength and durability, reduces the wear rate, and significantly improves the antifriction properties of the coating. The surfacing rods based on B83 babbit containing reinforcing particles for arc welding of coatings on steel substrate were produced by the extrusion method. These rods were characterized by lack of porosity and discontinuities in the internal volume as well as by defect-free surface. The density and hardness of the rods are comparable with the same characteristics of the cast babbitt. Arc welding of coatings was performed in the AC mode with a non-consumable tungsten electrode in an argon atmosphere. Welding current I = 160–170 А, arc voltage U = 16–18 V, welding rate Vw = 4.2 m/h, and protective gas (Ar) flow rate VAr = 12–14 L/min. The structure and tribological properties of the composite rods and coatings deposited were investigated with the help of electron and optical microscopy methods and under dry sliding friction tribological tests. The size of SnSb intermetallic compounds in the rods after extrusion and in the coatings deposited was determined. It was found that the size of intermetallic phases decreased by a factor of two after introduction of SiC and B4C particles into the babbitt alloy. The results of wear tests show that reinforcing and modifying the structure of the surfacing rods by introduction of high-strength micron- and submicron-sized ceramic SiC and B4C particles improves the antifriction properties of surfaced composite coatings. The friction coefficient of the composite coating was the same throughout the load interval, while for the unmodified babbit coating its value was by two times higher than that for the composite coating under a load up to 39 N and 20% higher under loads greater than 39 N. The coatings with high-strength SiC and B4C particles have a low coefficient of friction (0.4) and a high coefficient of the friction process stability (0.8).