INVESTIGATION OF FORMATION OF WEAR-RESISTANT ALLOY STRUCTURE IN SURFACING USING FLUX-CORED STRIP PL-AN-111

摘要

The investigations of temperature-time conditions of formation of microstructure of the alloy produced by electric arc surfacing of austenitic alloy of the type 500Kh40N40S2G1RTs using flux-cored strip PL-AN-111 were carried out. The investigation of structure formation of deposited bead over the height was carried out by modeling in the environment of the software product ProCAST. The modeling results were compared with the real microstructure of wear-resistant layer produced by electric arc surfacing using flux-cored strip PL-AN-111. The microstructure of a deposit was investigated on transverse microsections, etched with 4 % nital for a long time, using the optical microscope Nikon Eclipse M200 and the electron scanning microscope JSM-6510 LV, equipped with the EDS-analyzer of Oxford Instruments Company. The application of finite element modeling allowed establishing that the cooling rate of the bead of 10 mm height and 25 mm width, deposited applying the flux-cored strip PL-AN-111 on the plate 09G2S of 15 mm thickness, varies from 27.8 to 0.6 °C/s, decreasing with the increase in cooling time and removal from the fusion zone with the base. The crystallization of 500Kh40N40S2G1RTs type alloy takes place in the temperature range of 1332-1195 °C, starting with evolution of the primary carbides M_7C_3 and completing by the eutectic ?liquid → austenite + M_7C_3? transformation. The increase in cooling rate up to 27.8 °C/s suppresses the crystallization process of primary carbides M_7C_3, as a result of which a gradient structure is formed over the deposited layer height, varying from austenitic non-carbide (near the fusion boundary with the base) to the hypereutectic (in the upper part of the bead). At the cooling rate of 6.6 °C/s, the primary carbides M_7C_3 from the liquid are evolved in the interval of 1332—1274 °C, containing in average 57.6 % Cr and 2.7 % Ni, which corresponds to the thermodynamically stable state of the alloy of the 500Kh40N40S-2G1RTs type. 12 Ref, 6 Figures.