A one-dimensional penetration model has been developed to analyze the cold-gas dynamic spray process in hopes of establishing a constant minimum normalized penetration depth for particle adhesion. The simple model was in disagreement with results extrapolated from published copper-on-steel impact data. Possible reasons for the disagreement are discussed. A possible bonding mechanism is proposed that is dependent on the flow properties of both the particle and substrate.
A one-dimensional penetration model has been developed to analyze the cold-gas dynamic spray process in hopes of establishing a constant minimum normalized penetration depth for particle adhesion. The simple model was in disagreement with results extrapolated from published copper-on-steel impact data. Possible reasons for the disagreement are discussed. A possible bonding mechanism is proposed that is dependent on the flow properties of both the particle and substrate.
Your Guide to Advanced Cold Spray TechnologyCold Gas Dynamic Spray centers on cold gas dynamic spray (or cold spray-CS) technology, one of the most versatile thermal spray coating methods in materials engineering, and effectively describes and analyzes the main trends and developments behind the spray (coating) techniques. The book combines theory
The topic of this book is Cold Spray technology. Cold Spray is a process of applying coatings by exposing a metallic or dielectric substrate to a high velocity (300 to 1200 m/s) jet of small (1 to 50 μm) particles accelerated by a supersonic jet of compressed gas. This process is based on the selection of the combination of particle temperature, velocity, and size that allows spraying at the lowest temperature possible. In the Cold Spray process, powder particles are accelerated by the supersonic gas jet at a temperature that is always lower than the melting point of the material, resulting in coating formation from particles in the solid state. As a consequence, the deleterious effects of high-temperature oxidation, evaporation, melting, crystallization, residual stresses, gas release, and other common problems for traditional thermal spray methods are minimized or eliminated. This book is the first of its kind on the Cold Spray process. Cold Spray Technology covers a wide spectrum of various aspects of the Cold Spray technology, including gas-dynamics, physics of interaction of high-speed solid particles with a substrate as well as equipment, technologies, and applications. Cold Spray Technology includes the results of more than 20 years of original studies (1984-2005) conducted at the Institute of Theoretical and Applied Mechanics of the Siberian Division of the Russian Academy of Science, as well as the results of studies conducted at most of the research centres around the world. The authors' goal is threefold. The first goal is to explain basic principles and advantages of the Cold Spray process. The second goal is, to give practical information on technologies and equipment. The third goal is to present the current state of research and development in this field over the world. The book provides coverage and data that will be of interest for users of Cold Spray technology as well as for other coating experts. At the present time the Cold Spray method is recognized by world leading scientists and specialists. A wide spectrum of research is being conducted at many research centres and companies in many countries. New approach to spray coatings Results are exceptionally pure coatings Low spray temperature without degradation of powder and substrate materials High productivity, high deposition efficiency High operational safety because of absence of high temperature gas jets, radiation and explosive gases Excellent thermal and electrical conductivity Wide spectrum of applications because of important advantages of the process
In engineering, there are often situations in which the material of the main component is unable to sustain long life or protect itself from adverse operating environments. Moreover, in some cases, different material properties such as anti-friction and wear, anti-corrosive, thermal resistive, super hydrophobic, etc. are required as per the operating conditions. If those bulk components are made of such materials and possess those properties, the cost will be very high. In such cases, a practical solution is surface coating, which serves as a protective barrier to the bulk material from the adverse environment. In the last decade, with enormous effort, researchers and scientists have developed suitable materials to overcome those unfavorable operating conditions, and they have used advanced deposition techniques to enhance the adhesion and surface texturing of the coatings. Advanced Surface Coating Techniques for Modern Industrial Applications is a highly sought reference source that compiles the recent research trends in these new and emerging surface coating materials, deposition techniques, properties of coated materials, and their applications in various engineering and industrial fields. The book particularly focuses on 1) coating materials including anti-corrosive materials and nanomaterials, 2) coating methods including thermal spray and electroless disposition, and 3) applications such as surface engineering and thin film application. The book is ideal for engineers, scientists, researchers, academicians, and students working in fields like material science, mechanical engineering, tribology, chemical and corrosion science, bio-medical engineering, biomaterials, and aerospace engineering.
Proceedings of a symposium sponsored by Association for Iron and Steel Technology and the Process Technology and Modeling Committee of the Extraction and Processing Division and the Solidification Committee of the Materials Processing and Manufacturing Division of TMS (The Minerals, Metals & Materials Society) Held during the TMS 2012 Annual Meeting & Exhibition Orlando, Florida, USA, March 11-15, 2012
This book combines the contributions of experts in the field to describe the behavior of various materials, micromechanisms involved during processing, and the optimization of cold-spray technology. It spans production, characterization, and applications including wear resistance, fatigue, life improvement, thermal barriers, crack repair, and biological applications. Cold spray is an innovative coating technology based on the kinetic energy gained by particles sprayed at very high pressures. While the technique was developed in the 1990s, industrial and scientific interest in this technology has grown vastly in the last ten years. Recently, many interesting applications have been associated with cold-sprayed coatings, including wear resistance, fatigue life improvement, thermal barriers, biological applications, and crack repair. However, many fundamental aspects require clarification and description.
This book is a highly practical and useful ""go-to"" resource that presents an in-depth look at the high pressure cold spray process and describes applications in various industries. Cold spray continues to be the fastest developing spray technology over the last decade, and a significant number of scientists, engineers, and technologists are joining the cold spray community around the globe. The technology is relatively young and work is being simultaneously pursued in universities, research centers, and in many high tech industries. As this novel technology spreads quickly into many new application areas, there is a large need for an authoritative source of information. This new book addresses this need and will be indispensable to universities, libraries, and those involved in thermal spray. It presents baseline information on design and modeling, materials science of engineered coatings, and specific applications in various high tech industries, and is also a hands-on resource for cold spray operators.
Polyethylene particles of diameter 53-75 ̦um and density 0.94g/cm3, were cold spray deposited onto a metallic substrate. The particles were accelerated in air through a converging-diverging nozzle. Dense deposits were formed at temperatures substantially below the melting point of the polymer, and the critical impact velocity for deposit growth was found to be about 180 m/s. No apparent melting of the polymer particles was observed. The present study deals with the numerical and experimental investigation of the cold spray gas dynamic effects for spraying of polyethylene powder onto aluminum 7075-T6 substrates. A number of Computational Fluid Dynamics (CFD) models were created for various nozzle geometries and flow conditions. These models were used to provide insight into the detailed gas dynamic processes attendant to cold spray process and in particular the interaction of the carrier gas flow with the particle flow. A schlieren optical system was designed and implemented to visualize the density gradients in the supersonic free jet and impingement regions. Based on results from the CFD models it was determined that a diffuser placed into the carrier gas flow at the exit of the nozzle would create a lower particle impact velocities and more significantly, lower shear stresses in the substrate boundary layer, preventing inadvertent removal of previously deposited material. Experimental testing of the concept resulted in successful deposition of polyethylene power onto the 7075-T6 aluminum substrate with much improved deposition efficiency. Because of the complex interaction between the carrier gas dynamics and the particle dynamics, the CFD models were essential in creating new nozzle designs for the heretofore unsprayable polymer materials. In addition, the CFD models were used to suggest improved designs for spraying other types of powder materials, where increased particle impact velocity is required. Refinements to these concepts are currently under investigation and patent disclosure for the idea is pending.
This book first presents different approaches to modeling of the cold spray process with the aim of extending current understanding of its fundamental principles and then describes emerging applications of cold spray. In the coverage of modeling, careful attention is devoted to the assessment of critical and erosion velocities. In order to reveal the phenomenological characteristics of interface bonding, severe, localized plastic deformation and material jet formation are studied. Detailed consideration is also given to the effect of macroscopic defects such as interparticle boundaries and subsequent splat boundary cracking on the mechanical behavior of cold spray coatings. The discussion of applications focuses in particular on the repair of damaged parts and additive manufacturing in various disciplines from aerospace to biomedical engineering. Key aspects include a systematic study of defect shape and the ability of cold spray to fill the defect, examination of the fatigue behavior of coatings for structural applications, and a novel working window at subcritical conditions to obtain porous structures. This book is exceptional in scope, and its review of finite element modelling at different length scales sheds light on future design and process improvement in emerging applications such as structural repair, metal additive manufacturing and metal foam design.
