Film surface characterization in cold spray using advanced numerical modeling and simulation techniques
- Authors: Moonga, Kando Hamiyanze , Jen, TienChen
- Date: 2017
- Subjects: Multiple particle impact , Cold spray , Surface roughness
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/241971 , uj:24946 , Citation: Moonga, K.H. & Jen, T.C. 2017. Film surface characterization in cold spray using advanced numerical modeling and simulation techniques.
- Description: Abstract: In cold spray, even when the initial properties are within the critical values for deposition, the multi-impact process is much more complex to ensure a 100% deposition. In inelastic impact, part of the initial kinetic energy of the particles at impact is lost through plastic deformation. After impact and subsequent restitution, unbounded particles will be ejected through rebound forces or material jetting at erosion. Observation of the final kinetic energies achieved in the particles after impact was used as criteria for a rough estimate of the coating process. The surface roughness increased with reduced deposition efficiency. The interface roughness was less affected by this process. Qualitative comparison to experimental results shows some closer correlations with some of the surfaces of experimentally obtained surfaces in cold spray. This could provide some of the answers to the underlying mechanisms in which the cold spray surfaces are generated.
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Numerical analysis of the cold gas dynamic spray surface coating process
- Authors: Moonga, Kando Hamiyanze , Jen, Tien-Chen
- Date: 2017
- Subjects: Cold spray , Numerical analysis , Multiple particle impact
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/243771 , uj:25199 , Citation: Moonga, K.H & Jen, T.C. 2017. Numerical analysis of the cold gas dynamic spray surface coating process. Advances in Engineering Research (AER), volume 102, Second International Conference on Mechanics, Materials and Structural Engineering (ICMMSE 2017).
- Description: Abstract: In Cold Spray, bonding is formed between substrate and the particles and between particles by impact which causes material deformation and temperature rise. During impact process, plastic deformation and frictional interaction of materials generate heat and strains/stresses. In this paper, a numerical study on multiple particles deposition process show that the plastic equivalent strain (von misses stress) and the temperature values, compare to a single particle impact under same conditions, are higher in multiple particles compared to a single particle impact. Based on this observation, there is a possibility of the bonding mechanism for the whole film coating better explained using the multiple particles modeling than is predicted using single particle analysis However the actual impacting mechanism in the multiple particle interaction is not yet fully understood and still requires further investigation.
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Residual stress characterization from numerical analysis of the multi-particle impact behavior in cold spray
- Authors: Moonga, Kando Hamiyanze , Jen, Tien-Chien
- Date: 2017
- Subjects: Multiple particle impact , Cold spray , Residual stress
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/259242 , uj:27273 , Citation: Moonga, K.H. & Jen, T.C. 2017. Residual stress characterization from numerical analysis of the multi-particle impact behavior in cold spray.
- Description: Abstract: In cold spray, bonding is created between a substrate and the particles and between particles through impact deformation at high strain rates. A prominent feature of the cold spray process is the compressive residual stress that arises during the deposition process. Compressive residual stress on the surface can be beneficial for fatigue resistance. As a post processing technique several applications require surface treatment processes that produce this state of stress on component surfaces such as shot peening, laser shock peening, ultrasonic impact treatment, low plasticity burnishing, etc. In all of these methods the compressive stress is produced through plastic deformation of the surface region. In a similar manner, the cold spray process induces compressive stress by high speed impact of the sprayed particles on the surface, causing a peening effect. The effects of these variations in the properties of the coatings are rarely reported. Moreover there are some applications which require minimal residual stresses in the components such as in optics. In this study, we have investigated the residual stress using numerical analysis of the multi-particle impact behavior in cold spray.
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Microstructural and mechanical evaluation of laser-assisted cold sprayed bio-ceramic coatings : potential use for biomedical applications
- Authors: Tlotleng, Monnamme , Akinlabi, Esther Titilayo , Shukla, Mukul , Pityana, Sisa
- Date: 2014
- Subjects: Titanium , Laser power , Cold spray , Laser-assisted cold spray , Hydroxyapatite
- Type: Article
- Identifier: uj:5135 , ISSN 1544-1016 , http://hdl.handle.net/10210/14101
- Description: Bio-composite coatings of 20 wt.%, HAP and 80 wt.%, HAP were synthesized on Ti-6Al-4V substrates using LACS technique. The coatings were produced with a laser power of 2.5 kW, powder-laser spot trailing by 5 s. The coatings were analyzed for the microstructures, microhardness, composition, and bio-corrosion using SEM-EDS, XRD, hardness tester, and Metrohm PGSTAT101 machine. SEM images indicated least pores and crack-free coating with dark-spots of Ti-HAP for the 20 wt.%, HAP as opposed to the 80 wt.%, HAP coating which was solid, porous and finely cracked and had semi-melted Ti-HAP particles. The EDS mappings showed high content of HAP for the 80 wt.%, HAP coating. The diffraction patterns were similar, even though the Ti-HAP peak was broader in the 80 wt.%, HAP coating and the HAP intensities were lower for this coating except for the (004) peak. The hardness values taken at the interface inferred that the 80 wt.%, HAP coating was least bonded. It was possible to conclude that when this phase material increased the hardness dropped considerably. The bio-corrosion tests indicated that the presence of HAP in coating leads to a kinetically active coating as opposed to pure titanium coating.
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