PTA-P process: impact of powder feeding conditions on process characteristics and weld bead morphology

In the Plasma Transferred Arc with Powder (PTA-P) welding process, material feeding is significantly more complex than in conventional wire-based welding processes. The present study aims to elucidate powder feeding behavior as a function of carrier gas flow rate and powder feeding, and its impact on deposit morphology under fixed welding conditions and operational configurations. Carrier gas flow rates (1.0–4.0 L/min) and powder-feed device speeds (1–5 RPM; 0.7–3.6 kg/h) were systematically combined using Inconel 625 and a powder stratification device to characterize distribution across torch channels. Welding tests followed at 130 A welding current, 10 cm/min travel speed, and 1.0 kg/h powder feeding rate with carrier gas flow rates of 0.5, 1.0, and 2.0 L/min. Results reveal three distinct powder distribution patterns for different carrier gas flow rates: uniform at 1.0 L/min; predominantly front channels at 2.0 L/min; and predominantly rear channels at 0.5 L/min. Uniform feeding achieved highest deposition and melting efficiency, process stability, uniform penetration, and consistent weld bead dimensions, while unbalanced patterns proved unsuitable. These findings highlight the critical role of powder distribution—dependent on torch geometry and injection architecture—for PTA-P productivity and reliability.