ABSTRACT Electrolytic hard chrome (EHC) methods are still widely utilized in the printing, automo... more ABSTRACT Electrolytic hard chrome (EHC) methods are still widely utilized in the printing, automotive and off-shore industries. Alternative methods to EHC have been widely developed in the past decade by conventional HVOF processes and more recently HVAF systems, which are processing at higher kinetic energy and more particularly at lower temperature, significantly increasing wear and corrosion resistance properties. A dedicated internal diameter HVAF system is here presented, and coatings characteristics are compared to the one obtained by standard HVAF coatings. Specially R&D designed fixtures with inside bore of 200 mm have been manufactured for this purpose, with a possibility to spray samples at increasing depth up to 400 mm while simulating closed bottom bore spraying. WC-based and Cr3C2-based powder feedstock materials have been deposited onto high-strength steel substrates. Respective coating microstructures, thermally induced stresses and corrosion resistance are discussed for further optimization of coating performances. The fact that the ID-HVAF system is utilized both for spraying and gritblasting procedures is also given a particular interest.
ABSTRACT Replacement of electrolytic hard chromium method by thermal spray technology has shown a... more ABSTRACT Replacement of electrolytic hard chromium method by thermal spray technology has shown a growing interest in the past decades, mainly pioneered by depositing WC-based material by conventional HVOF processes. Lower thermal energy and higher kinetic energy of sprayed particles achieved by newly developed Supersonic Air Fuel system, so-called HVAF-M3, significantly reduces decarburization, and increases wear and corrosion resistance properties, making HVAF-sprayed coatings attractive both economically and environmentally. In the present work, full factorial designs of experiments have been extensively utilized to establish relationships between hardware configurations, process and engineering variables, and coatings properties. The relevance of those process factors is emphasized and their significance is discussed in the optimization of coatings for improved abrasion wear and corrosion performances.
Residual stress buildup in thick thermal spray coatings is a property of concern. The adhesion of... more Residual stress buildup in thick thermal spray coatings is a property of concern. The adhesion of these coatings to the substrate is influenced by residual stresses that are generated during the coating deposition process. In the HVOF spray process, significant peening stresses are generated during the impact of semimolten particles on the substrate. The combination of these peening stresses together with quenching and thermal mismatch stresses that arise after deposition can be of significant importance. Both numerical method, i.e., Finite Element Method (FEM), and experimental methods, i.e., the Modified Layer Removal Method (MLRM) and Neutron Diffraction, to calculate peening and quenching stresses have been utilized in this work. The investigation was performed on thick Inconel 718 coatings on Inconel 718 substrates. Combined, these numerical and experimental techniques yield a deeper understanding of residual stress formation in the HVOF process and thus a tool for process optimization. The relationship between the stress state and deposit/substrate thickness ratio is given particular interest.
ABSTRACT This paper provides a comprehensive assessment of the sliding and abrasive wear behaviou... more ABSTRACT This paper provides a comprehensive assessment of the sliding and abrasive wear behaviour of WC-10Co4Cr hardmetal coatings, representative of the existing state-of-the-art. A commercial feedstock powder with two different particle size distributions was sprayed onto carbon steel substrates using two HVOF and two HVAF spray processes.
ABSTRACT Electrolytic hard chrome (EHC) methods are still widely utilized in the printing, automo... more ABSTRACT Electrolytic hard chrome (EHC) methods are still widely utilized in the printing, automotive and off-shore industries. Alternative methods to EHC have been widely developed in the past decade by conventional HVOF processes and more recently HVAF systems, which are processing at higher kinetic energy and more particularly at lower temperature, significantly increasing wear and corrosion resistance properties. A dedicated internal diameter HVAF system is here presented, and coatings characteristics are compared to the one obtained by standard HVAF coatings. Specially R&D designed fixtures with inside bore of 200 mm have been manufactured for this purpose, with a possibility to spray samples at increasing depth up to 400 mm while simulating closed bottom bore spraying. WC-based and Cr3C2-based powder feedstock materials have been deposited onto high-strength steel substrates. Respective coating microstructures, thermally induced stresses and corrosion resistance are discussed for further optimization of coating performances. The fact that the ID-HVAF system is utilized both for spraying and gritblasting procedures is also given a particular interest.
ABSTRACT Replacement of electrolytic hard chromium method by thermal spray technology has shown a... more ABSTRACT Replacement of electrolytic hard chromium method by thermal spray technology has shown a growing interest in the past decades, mainly pioneered by depositing WC-based material by conventional HVOF processes. Lower thermal energy and higher kinetic energy of sprayed particles achieved by newly developed Supersonic Air Fuel system, so-called HVAF-M3, significantly reduces decarburization, and increases wear and corrosion resistance properties, making HVAF-sprayed coatings attractive both economically and environmentally. In the present work, full factorial designs of experiments have been extensively utilized to establish relationships between hardware configurations, process and engineering variables, and coatings properties. The relevance of those process factors is emphasized and their significance is discussed in the optimization of coatings for improved abrasion wear and corrosion performances.
Residual stress buildup in thick thermal spray coatings is a property of concern. The adhesion of... more Residual stress buildup in thick thermal spray coatings is a property of concern. The adhesion of these coatings to the substrate is influenced by residual stresses that are generated during the coating deposition process. In the HVOF spray process, significant peening stresses are generated during the impact of semimolten particles on the substrate. The combination of these peening stresses together with quenching and thermal mismatch stresses that arise after deposition can be of significant importance. Both numerical method, i.e., Finite Element Method (FEM), and experimental methods, i.e., the Modified Layer Removal Method (MLRM) and Neutron Diffraction, to calculate peening and quenching stresses have been utilized in this work. The investigation was performed on thick Inconel 718 coatings on Inconel 718 substrates. Combined, these numerical and experimental techniques yield a deeper understanding of residual stress formation in the HVOF process and thus a tool for process optimization. The relationship between the stress state and deposit/substrate thickness ratio is given particular interest.
ABSTRACT This paper provides a comprehensive assessment of the sliding and abrasive wear behaviou... more ABSTRACT This paper provides a comprehensive assessment of the sliding and abrasive wear behaviour of WC-10Co4Cr hardmetal coatings, representative of the existing state-of-the-art. A commercial feedstock powder with two different particle size distributions was sprayed onto carbon steel substrates using two HVOF and two HVAF spray processes.
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Papers by C. Lyphout