Characteristics of Conventional and Cascaded Arc Plasma Spray-Deposited Ceramic Under Standard and High-Throughput Condi
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Characteristics of Conventional and Cascaded Arc Plasma Spray-Deposited Ceramic Under Standard and High-Throughput Conditions Ramachandran Chidambaram Seshadri1 • Sanjay Sampath1
Submitted: 29 October 2018 / in revised form: 23 January 2019 / Published online: 4 February 2019 ASM International 2019
Abstract Cascaded arc plasma torches have now become mainstream in thermal spray industry incorporating both multiple and single cathode configurations. Although there are anecdotal descriptions available for cascaded arc torches in terms of enhanced melting capability and overall process reliability, a critical and direct comparison of material interaction between the two technologies (cascaded arc and conventional torch configurations) through robust scientific methods is not available. In this article, two commercially available APS torches, namely, the conventional torch (F4MB) and the cascaded arc plasma torch (Sinplex Pro), were compared in the same spray cell using the same control equipment by adopting a systematic set of experiments involving voltage measurements, particle behavior, deposit formation dynamics, and infraredbased spray footprint heat flux quantification. The analysis of the data has led to quantitative correlations between torch configurations. The powder loading study indicated the enhanced melting capability of cascaded arc at equivalent parameters along with expanded and more uniform particle temperature over larger feed rates. The combination of higher feed rate and melt efficiency leads to distinction in coating stress evolution and microstructure. The integrated measurements suggest a scaling parameter that can establish process equivalency parameters to guide the transition from conventional to cascade torches.
& Sanjay Sampath [email protected] Ramachandran Chidambaram Seshadri [email protected] 1
Center for Thermal Spray Research (CTSR), Stony Brook University, Stony Brook, NY 11790, USA
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Keywords atmospheric plasma spray (APS) diagnostics in-situ monitoring on-lineparticle behavior spray efficiency stability ofTS process zirconia
Introduction Among the thermal spray processes, the atmospheric plasma spray (APS) process is the most flexible and widely used technology for depositing alloys, composites, and ceramics. Despite being a well-established industrial technology, the reliability and reproducibility of APS coatings are limited due to the transient and dynamic nature of the process (Ref 1). The properties of an APS coating can be a function of three interdependent subsystems: (1) the formation of the plasma jet, (2) injection and processing of the powder material in the plasma jet issuing from the torch and mixing with the surrounding gas, and (3) impact and solidification of the particles on the substrate (Ref 2). These subsystems must be diligently monitored, finely controlled, and made to work in a synergistic manner to obtain reliable and repeatable coating deposits. It is well known that the electrode life, thermal efficiency, and
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