On deposition of Waspaloy coatings by cold spray

Abstract

he deposition of pore free and highly adhered Ni and Co superalloy coatings is of great interest for engine design and gas turbine applications, both in oase of maintenance repair and overhaul operations as well for mechanical and chemical protection purposes in aeronautics and energy applications. This study would like to give a wide overview about the capability of cold spray technology on this topic: two different commercially available deposition systems, Sulzer-CGT Kinetiks 4000 and Plasma Giken PCS-1000, were compared, and deposition processes with both nitrogen and helium as carrier gas have been explored. Microstructural investigation, microhardness and adhesion results are reported to depict a preliminary scenario of coating properties. Fully dense coatings with thickness >1 mm and adhesion >50 MPa are obtained using helium, while quite porous, 20 MPa adhered coatings are obtained using nitrogen. Finally, general considerations about the potential applicability of those coatings for repair purpose in aerospace applications are pointed out.

A perspective review on the bonding mechanisms in cold gas dynamic spray

“…Generally speaking, the particles impact velocity and temperature mainly depend on the initial parameters of the propellant gas [86]; Schmidt et al [87] showed that optimised particle injection and the high propellant gas temperature significantly increase the particle impact velocity and the temperature. In the last two decades a lot of studies have been carried out to better explain the interfacial bonding mechanisms as well as the effect of the deposition parameters on cold-sprayed coatings quality and microstructure [88][89][90][91][92][93]; the present review paper aims to summarise the main studies carried out up to now on the phenomena of the coating formation and the particle deformation mechanisms in cold spray processes.…”

Wear-resistant cobalt-based coatings for injection moulds by cold spray

“…b Microporosity due to lack of particle-particle bonding; micrography of Waspaloy coatings deposited by cold spray. 9 (c) Porosity due to particle removal during preparation of a specimen coated by Stellite 31 + 10 wt-% of AISI 316L. Red dots emphasise each kind of defects multi-alloy coatings as in this case, a certain lack of cohesion in coating microstructure leads to particle abrasion and removal during preparation.…”

“…5 In recent years, cold gas dynamic spray (CS) is receiving an increasing consideration because of its low spraying temperature and opportunities in the deposition of both metal-based oxygen sensitive and high strength metal-based materials, such as Stellite 6, Inconel 718, Waspaloy and aluminium. [6][7][8][9] CS is a thermal-spray technique but it remains a solidstate powder deposition process avoiding melting or partial melting of spraying particle and preventing the heat-affected zone. 10 Thanks to this advantage, ductile metallic coatings as copper and aluminium were used in restoring application for aircraft structural parts and injection moulding dies.…”

Effect of Pulsed Waterjet Surface Preparation on the Adhesion Strength of Cold Gas Dynamic Sprayed Aluminum Coatings

“…However, radially injected particles can either be directed into the gas in the upstream (high-pressure) section or the downstream (lowpressure) section of the nozzle, relative to the throat. Generally, CGDS processes can operate at temperatures between room temperature up to~1000°C and pressures up to 5 MPa ( Ref 7,9).…”