Shock-wave induced spraying: Gas and particle flow and coating analysis

• Published in: Surface & coatings technology 2012-08, Vol.207, p.435-442
• Main Authors: Karimi, Mo, Rankin, Gary W., Jodoin, Bertrand
• Format: Article
• Language: English
• Subjects: Applied sciences; Cold spray; Computer simulation; Cross-disciplinary physics: materials science; rheology; Discrete phase modeling; Exact sciences and technology; Gas dynamics; Materials science; Metals. Metallurgy; Modeling; Physics; Production techniques; Shock-wave induced spraying process; Surface treatment; Surface treatments
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2012.07.044

Computational fluid dynamics (CFD) is used to model the shock-wave induced spray process (SISP). SISP is a method of applying coatings of various metallic-based materials onto a substrate. It utilizes the kinetic and thermal energy induced by a moving shock-wave to accelerate and heat powder particles. This process is a new cold gas-dynamic spraying (CGDS or simply cold spray) material deposition technique. The basic principles related to the coating formation and bonding mechanism in this process are hypothesized to be similar to those in traditional Cold Spray processes. The distinguishing feature of SISP is a sequence of moving shock-waves created by the fast opening and closing of a valve. A rate of 30 to 50 pulses per second is presently conceivable. When the valve is rapidly opened and closed, a shock-wave propagates into the spraying gun, accelerating and heating the powder present in the gun. Similar to the cold spray process, the particles then impact the substrate and deform plastically to produce a coating. Individual powder particles may reach the substrate at different velocities and temperatures depending on their location within the unsteady flow regime. An existing correlation for the “critical velocity” for bonding and a CFD model are used to predict whether a particle traveling within this unsteady flow regime will adhere to the substrate upon impact. This information is then used to predict if a coating can be formed under a specific set of spray conditions. ► A new model of the shock-wave induced spraying process is presented and validated. ► Interesting results of the transient gas flow and particle behavior are shown. ► Coating formation is predicted using available correlation for critical velocity. ► Prediction trends agree with experimental results.