Tungsten Heavy Alloys from Mixed Feedstock by RF Plasma

• Published in: Journal of thermal spray technology Vol. 32; no. 8; pp. 2747 - 2762
• Main Authors: Kovarik, Ondrej, Cizek, Jan, Klecka, Jakub, Karlik, Miroslav, Cech, Jaroslav, Kozlik, Jiri, Lauschmann, Hynek
• Format: Journal Article
• Language: English
• Published: New York Springer US 01-12-2023
• Subjects: Analytical Chemistry; Characterization and Evaluation of Materials; Chemistry and Materials Science; Corrosion and Coatings; Machines; Manufacturing; Materials Science; Original Research Article; Processes; Surfaces and Interfaces; Thin Films; Tribology; stress-strain; additive manufacturing; fatigue crack growth rate; fracture toughness; inert atmosphere
• ISSN: 1059-9630; 1544-1016
• DOI: 10.1007/s11666-023-01647-6

Tungsten heavy alloys (WHA) are particulate composites of spherical W particles embedded in a ductile Ni-rich matrix. In our study, pre-treated W and Ni feedstock powders were used to prepare three different compositions (all wt.%) for spraying: W-10Ni, W-20Ni for two different WHA, and W-65Ni for a matrix-only material without the reinforcing W particles. Using radio frequency inductively coupled plasma spraying (RF-ICP) method, low porosity deposits were obtained with ductility exceeding 5%. By a detailed study of the microstructure and the particle-matrix interfaces, the mechanism of the composite formation was identified: a rapid dissolution of W in the liquid Ni and a subsequent W particle solidification followed by the solidification of the matrix. The mechanical properties of the composites are defined by the Ni-rich matrix (tough and significantly stronger than pure Ni) with well bonded stiff W particles. The elastic behavior was related to the W content following the Reuss model, describing a layered composite modulus in a serial configuration. Contrary to this, in the plastic regime, all WHA exhibited nearly identical behavior regardless of the W content. In this regime, the deformation of the W particles reached several percent, indicating an extremely strong particle-matrix bonding. Last, the failure mechanisms of the materials were investigated, with the matrix behavior governing the fatigue failure, and particle-matrix decohesion dominating in the static loading at higher loads.