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Influence of Particle Velocity When Propelled Using N2 or N2-He Mixed Gas on the Properties of Cold-Sprayed Ti6Al4V Coatings

1
[email protected] Corporate Lab, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
2
School of Mechanical & Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
3
Facility for Analysis, Characterisation, Testing and Simulation (FACTS), Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
4
Singapore Institute of Manufacturing Technology (SIMTech), 73 Nanyang Drive, Singapore 637662, Singapore
5
Advanced Technology Centre, Rolls-Royce Singapore Pte Ltd., 1 Seletar Aerospace Crescent, Singapore 797575, Singapore
6
School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
*
Author to whom correspondence should be addressed.
Coatings 2018, 8(9), 327; https://doi.org/10.3390/coatings8090327
Received: 12 July 2018 / Revised: 30 August 2018 / Accepted: 7 September 2018 / Published: 18 September 2018
(This article belongs to the Special Issue From Metallic Coatings to Additive Manufacturing)
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Abstract

Cold-spraying is a relatively new low-temperature coating technology which produces coatings by the deposition of metallic micro-particles at supersonic speed onto target substrate surfaces. This technology has the potential to enhance or restore damaged parts made of light metal alloys, such as Ti6Al4V (Ti64). Particle deposition velocity is one of the most crucial parameters for achieving high-quality coatings because it is the main driving force for particle bonding and coating formation. In this work, studies were conducted on the evolution of the properties of cold-sprayed Ti64 coatings deposited on Ti64 substrates with particle velocities ranging from 730 to 855 m/s using pure N2 and N2-He mixture as the propellant gases. It was observed that the increase in particle velocity significantly reduced the porosity level from about 11 to 1.6% due to greater densification. The coatings’ hardness was also improved with increased particle velocity due to the intensified grain refinement within the particles. Interestingly, despite the significant differences in the coating porosities, all the coatings deposited within the velocity range (below and above critical velocity) achieved a high adhesion strength exceeding 60 MPa. The fractography also showed changes in the degree of dimple fractures on the particles across the deposition velocities. Finite element modelling was carried out to understand the deformation behaviour of the impacting particles and the evolutions of strain and temperature in the formed coatings during the spraying process. This work also showed that the N2-He gas mixture was a cost-effective propellant gas (up to 3-times cheaper than pure He) to deliver the high-quality Ti64 coatings. View Full-Text
Keywords: high-pressure cold spray; Ti6Al4V powder/coating/substrate; particle velocity; N2-He gas mixture; adhesion strength; finite element modelling high-pressure cold spray; Ti6Al4V powder/coating/substrate; particle velocity; N2-He gas mixture; adhesion strength; finite element modelling
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Tan, A.W.; Lek, J.Y.; Sun, W.; Bhowmik, A.; Marinescu, I.; Song, X.; Zhai, W.; Li, F.; Dong, Z.; Boothroyd, C.B.; Liu, E. Influence of Particle Velocity When Propelled Using N2 or N2-He Mixed Gas on the Properties of Cold-Sprayed Ti6Al4V Coatings. Coatings 2018, 8, 327.

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