Gas-Shielded Tungsten Arc Welding (GTAW) was modified to a Flux-Cored-Double-Wire GTAW (FCDW-GTAW); in this technique, wires of different compositions are used simultaneously to obtain different microstructures. In the modified GTAW, automatic flux-cored double-wire was used with a combination of four different wires deposited in AISI1020 steel, allowing different microstructures. Pin-on-disk wear tests described by ASTM G99 was used to evaluate the wear coefficients of four hardfacing materials combining Fe–Cr–C, Fe-Cr-C-Nb, Fe-Cr-C-Mo-Nb, and Fe-Cr-C-Mo-Ti alloys. The combination of these wires resulted in a hypoeutectic microstructure with niobium and titanium carbides, with an average hardness of 650 HV0.3, and hypereutectic microstructures formed by different niobium contents, with a microhardness range from 820 to 1020 HV0.3. The wear tests were performed without lubrication at room temperature, using a 6.0 mm diameter polished alumina sphere as a counter-body. The total distance covered was 1000 m with a speed of 0.1 m/s, a track radius of 6.0 cm, and an applied load of 10 N. Hardness, microstructure, wear coefficient, and wear mechanisms were compared. The results showed that wear resistance could be differentiated by the predominant wear mechanism: polishing for the hypoeutectic hardfacing and cracking for the hypereutectic ones.

ABSTRACT The hardfacing deposition with the GTAW process is widely studied with the addition of metallic powder or solid wire. This study introduces an original method, flux-cored-double-wire GTAW (FCDW-GTAW), where wires of different compositions are used simultaneously to deposit hardfacing. Because of the complexity in stabilizing the welding system, the combined effects of welding parameters should be investigated, allowing elaborate prediction models for the geometry and dilution of the deposits. These aspects are crucial for the target application, wear-resistant layers based on Fe-Cr-C composition, requiring a low-level of dilution and bead-geometry quality. Five parameters were chosen to model the deposition: the welding current, welding speed, standoff distance, torch angle, and wire feed pulse frequency. Therefore, using Response Surface Methodology with five factors at five levels to plan the experiments, thirty-two deposition conditions were necessary to model responses. Complete and reduced models were presented for width, reinforcement, penetration, and dilution responses. The reduced models showed a better prediction than the complete ones. The welding parameters’ interaction was identified for the reduced models, where the welding current and speed were influential in all responses. Results showed the possibility of obtaining good quality in the beads applying the FCDW-GTAW technique.

Neste trabalho estudou-se a perda de massa de revestimento duro aplicado pelo processo de soldagem com arame tubular com a variação de energia de soldagem, gás de proteção e número de camadas do revestimento. Com arame tubular autoprotegido de liga Fe-Cr-C-Ti foram depositados cordões sobrepostos na formação de camadas de revestimento sobre chapas de aço ao Carbono AISI 1020 para a análise da perda de massa, dureza, microestrutura. Foram realizadas medições de dureza na superfície dos corpos de prova de desgaste. Abrasômetro tipo roda de borracha foi usado para determinar a perda de massa dos revestimentos. Os revestimentos apresentaram microestrutura martensítica e austenita retida com carbonetos finamente dispersos na matriz. Os principais fatores que contribuíram para o aumento na perda de massa foram as trincas devido a maior taxa de resfriamento das amostras depositadas com baixa energia de soldagem, a diluição na primeira camada de todas as amostras também contribuiu para o aumento na perda de massa. As menores perdas de massa foram dos revestimentos de duas e quatro camadas depositados com alta energia de soldagem. A fração volumétrica de carbonetos de Titânio contribuiu para a diminuição do caminho livre médio entre as partículas de carbonetos aumentando a resistência ao desgaste dos revestimentos.

In this papper, have been studied the mass loss of hardfacing applied by flux cored arc welding. Heat input, shielding gás and number of layers coating were changed to application of Fe-Cr-Ti-C self-shielded tubular wire. Beads overlapped were deposited on plates of carbon steel AISI 1020 to analyze the mass loss, hardness and microstructure. For the analysis of mass loss were deposited beads forming overlapped layers coatings. Hardness measurements were performed on the surface of the specimens of wear. Rubber wheel abrasion tester was used to access the mass loss of coatings. The coatings had retained austenite and martensite microstructure with carbides finely dispersed in the matrix. The main factors that contributed to the increase in mass loss were the cracks due to higher cooling rate of the samples deposited with low heat input, the dilution in the first layer of all samples also contributed to the increase in mass loss. The smallest mass losses were those deposited coatings with high heat input the second and fourth layer, the samples AC2, AC4 and AS2. The volume fraction of titanium carbides contributed to the decrease in the mean free path between the particles of carbides increase the wear resistance of the coatings.