Characterization and Optimization of Ni-WC Composite Weld Matrix Deposited by Plasma-Transferred Arc Process
- PDF / 6,342,211 Bytes
- 11 Pages / 593.972 x 792 pts Page_size
- 43 Downloads / 202 Views
NTRODUCTION
HARDFACING by plasma transferred arc welding (PTAW) is widely used in deposition of wear-resistant coatings on to the surface of metals with applications ranging from machinery components operating under harsh working conditions up to aeronautical applications.[1] PTAW has many beneficial features: low cost, low heat input, high efficiency, easy operation, synchronized powder-feeding mechanism and automation simplicity.[2–5] The most widely used materials for wear resistant overlays are nickel- and iron-based powders mixed with tungsten carbide (WC) particles, providing M7 C3 carbide phase during solidification. Nickel-based alloys allow achievement of better abrasion and corrosion resistance at reasonably low material/processing cost. The majority of WC phases in conventional hardfacing are eutectoid W2 C/WC particles with about 3.7-4.1 wt pct of carbon[2] with high combined impact/ abrasion properties.[6] However, this phase has poor oxidation resistance under T >823 K ð550 C).[7] The dissolution of carbide particles favors formation of
ALI TAHAEI, MATTIA MERLIN, and GIAN LUCA GARAGNANI are with the Department of Engineering, University of Ferrara, Via G. Saragat 1, 44122 Ferrara, Italy. PAUL HORLEY, DAVID TORRES-TORRES, and ANA ARIZMENDIMORQUECHO are with Centro de Investigacio´n en Materiales Avanzados S.C. (CIMAV), UNIDAD Monterrey, Alianza Norte 202, 66628 Parque PIIT, Apodaca, Nuevo Leo´n, Mexico. Contact e-mail: [email protected] ROLANDO PRAGA and FELIPE J. GARCI´A VA´ZQUEZ are with the Corporacio´n Mexicana de Investigacio´n en Materiales S.A. de C.V. (COMIMSA), Ciencia y Tecnologı´ a 790, 25290 Saltillo-400, Saltillo, Coahuila, Mexico. Manuscript submitted March 30, 2016. METALLURGICAL AND MATERIALS TRANSACTIONS A
secondary phases, elongated tungsten-rich precipitates, and a small concentration of W ending up in solid solution.[8, 9] Adding Cr (about 14 wt pct) to the matrix alloy causes a significant fraction of secondary carbides to precipitate during WC dissolution process.[10,11] The major issues in achieving optimal performance of the Ni-WC composite overlays are nonuniform distribution and degradation/dissolution of the carbide particles. The importance of dilution is paramount, as it significantly alters the substrate properties and considerably reduces overlay wear resistance. The dilution in welds is directly related to the heat input during the welding process.[6] When depositing Ni-WC overlays, the settling of carbides produces a zone of low wear resistance on top of the hardfacing. Therefore, the final microstructure and phases are influenced by many technological parameters including welding current, nozzle travel speed and oscillation amplitudes, substrate preheating, and choice of a welding gas. Important studies had been dedicated to modeling and prediction of molten pool dimensions in PTAW process, aiming to understand the influence of deposition parameters (including weld bead width, height, aspect ratio, and dilution).[3,12–17] Despite these achievements, the question of
Data Loading...
