THE STUDIES OF COATINGS ON STEEL PRODUCTS APPLIED BY USING THE GAS POWDER LASER SURFACING
The application of wear-resistant coatings is purposed to solve the problem of restoration the parts subject to intensive wear. Various technological processes of applying metal coatings, including laser surfacing, are used. The use of laser beams for surfacing provides a small dissolution of the substrate in the welded layer, good adhesion to the base metal and high quality of the deposited layer. The peculiarities of the processes of obtaining surface coatings depend, to a large extent, on the type and form of the filler material and on the methods of its introducing into the zone of laser treatment. As a result of the study on applying the PG-C3P2, PN77X15S3R2-4Fe, BH, PG-FBX-6-2 and PG-US25 powders in the process of surfacing, there were determined the treatment modes and coating properties, without the influence of the base metal. The special rollers were welded on the samples, with the power of 1.0-1.5 kW and speeds of 10, 15 and 20 m/h. The beam was scanned along the circular trajectory, which left a spiral trace on the surface of the sample, taking into account the translational motion. Evaluation of the welding and microhardness quality was carried out on the cross-section of the metallographic grinding, with pores, cracks, non-melting, nonmetallic inclusions having been identified. The most qualitative surfacing was obtained, using PG-US25 powder. It differed from BX and PG-FBX-6-2 because it did not contain boron, but included 1.0-1.8% nickel. With this combination of chemical elements, the hardness of the surfacing was somewhat lower (8-9 GPa), but its formation was of higher quality. The pores and cracks in the deposited layer were in those cases, when the welded-on powder was mixed with the base metal.