• Guilemany, Josep Maria

Abstract

BRIEF SUMMARYThe present book covers the main aspects relating to fundamentals and applications of HVOF spraying. The first chapter deals with the basic methods of characterisation of materials structure, which include optical microscopy, transmission electron microscopy and scanning electron microscopy. There are many references in literature relating to the standard methods of characterisation, however, we guess that a very simple general view on theses issues would help the readers to refresh their memories.The issues related to powders for HVOF spraying (powder materials and methods of powder manufacturing and evaluation) are described in the second chapter. The third chapter is devoted to the methods of coating evaluation and includes evaluation of the coating structure and properties.The systems of HVOF spraying are presented in the fourth chapter, which deals with the description of the process, gaseous and liquid fuels for HVOF spraying, HVOF spray guns and future trends in HVOF spraying. The in-flight behaviour of the powder particles during the spray process is considered in the fifth chapter, which includes combustion and spraying gas dynamics, fundamentals of the in-flight behaviour and the results of mathematical modelling. The sixth chapter is dedicated to the coating deposition, flattening of droplets and formation of splats on the substrate surface and covers the issues related to the influence of solidification and surface roughness, effect of wetting and surface phenomena, influence of substrate deformation, flattening of the composite powder particles, splat-substrate mechanical interaction, dynamics of splashing, spraying at off-normal angles and influence of oxidation on the splat formation. The coating solidification and formation of the coating structure are considered in the seventh chapter which is related to the coating-substrate thermal interaction, formation of the interfacial region, development of the coating crystalline and amorphous structure, formation of the coating gas and shrinkage porosity and chemical in homogeneity. The development of the substrate-coating adhesive bonds is described in the eighth chapter, which includes different mechanisms of adhesion (mechanical, thermal, diffusive and chemical), influence of oxidation and residual stresses on the substrate-coating bonding. The theoretical results obtained are compared with the experimental data for the HVOF sprayed coatings. When these data are available the obtained analytical results (e.g., those established in the chapter 6) which are valid for the deposits developed by different types of thermal spraying, are compared with the experimental data for the plasma sprayed coatings. The chapter 9-12 deal with the structure-property relationships the coatings formed by HVOF spraying of the different cermet powders (WC-Co, WC-Co-Cr, Cr3C2-NiCr and TiC-Ni). Microstructure of the substrate interfacial region developed during HVOF spraying of these coatings is analysed in the thirteenth chapter. The results on the structure-property relationships in the coatings manufactured from metals (stainless steel and superalloys), ceramic and polymers are presented in the chapters 14 and 15. The chapter 16 is devoted to a new technology HVOF spray forming and describes preparation of the powders for forming, experimental procedure, results on evaluation of the structure and properties of the formed components. Some engineering applications of HVOF sprayed coatings are considered in the final chapter 17.

Topics

• Deposition
• impedance spectroscopy
• surface
• polymer
• amorphous
• stainless steel
• scanning electron microscopy
• composite
• combustion
• transmission electron microscopy
• forming
• porosity
• ceramic
• optical microscopy
• solidification
• superalloy