D Project D2: Surface coatings and cladding
Project Leader: Dr. Ming-Xing Zhang - University of Queensland
Staff/students
D3.1 Kinetic Metallization  
Zhang, Ming-Xing
Spencer, Kevin
Soria, Julio
Han, Joe
Li, Shuo
Redressing the lack of understanding of the physical bonding mechanism between the substrates and the coatings generated by kinetic metallization (KM) through TEM examination. To investigate the effects of KM treatment parameters, including powder particle flow velocity, particle size, treatment temperature (below 250C), time, distance between the supersonic nozzle and the substrate surface and the composition of the coating powder mixture, on the quality of coatings. Based on these results to deposit various high quality surface coatings on light metals in order to improve their wear resistance and corrosion resistance.
D3.2 Cold Spray
“Cold sprays” or more properly, cold-gas dynamic-spray process, is a high-rate coating and free-form fabrication process in which fine, solid powder particles, typically 1-50 µm in diameter, are accelerated via drag to velocities ranging between 500 and 1000 m/s using a supersonic gas jet. The solid particles are directed toward a substrate, where upon impact, they undergo plastic deformation and bond to the surface, rapidly building up a layer of the depositing material. One of the critical parameters in cold spray coating is the impinging particle velocity of the coating particle on the substrate. As the cold spray process control depends entirely on the supersonic particle-laden gas flow, the geometric arrangement and parameters of the nozzle and the substrate, it is imperative to understand the flow physics of the compressible two-phase flow within the converging-diverging nozzle and the supersonic two-phase gas flow outside the nozzle and its impingement on the substrate including interaction with shock waves.
Understanding the complex compressible flow and the trajectories of the powder particles is essential in the development of realistic physical models that describe the evolution history of the powder particles and their interaction with the substrate. The understanding of the complex physics and the models are crucial in the design and efficient application of cold spray technology to complex geometric components and in free-form fabrication processes. This requires prior knowledge of the gas flow field. It is clear from the literature review that current understanding of the fluid dynamics behind the process is still in a state of infancy. The aim of the current project is to employ computational fluid dynamics as a research tool for providing insight into the fluid dynamics behinds the compressible two-phase flow impinging onto the substrate.