In this study, WC-CoCr coatings are deposited on grit-blasted steel substrates by high-velocity airfuel (HVAF) spraying. A cross-sectional image of the feedstock powder shows that the WC grains are evenly distributed in the Co-Cr matrix. As-sprayed coating cross-sections are examined under different levels of magnification, coating hardness is measured, and coating and powder phases are analyzed by XRD. In addition, the corrosion behavior of coated and uncoated substrates is analyzed and compared with a reference hard chrome coating.

This study investigates the effect of gas composition on the flow characteristics of a three-cathode air plasma torch. A numerical model that couples fluid dynamic, electromagnetic, and thermal relationships is used to simulate temperature and velocity fields at the outlet of the torch. Different gases, including argon, nitrogen, and hydrogen, and gas mixtures are examined in the context of the study. The results show that the use of N 2 or H 2 as a secondary gas improves the output power and efficiency of the torch.

New developments in the field of thermal spraying systems (increased particle velocities, enhanced process stability) are leading to improved coating properties. At the same time innovations in the field of feedstock materials are supporting this trend. The combination of modern thermal spraying systems and new material concepts has led to a renaissance of Fe-based feedstocks. Using modern APS or HVOF systems, it is now possible to compete with classical materials for wear and corrosion applications like Ni basis (e.g. NiCrBSi) or metal matrix composites (MMC, e.g. WC/Co or Cr 3 C 2 /NiCr). The work described in this paper focuses on that combination and intends to give an analysis of the in-flight particle and spray jet properties achievable with two different modern thermal spraying systems (kerosene driven HVOF system K2, 3- cathodes APS system TriplexPro-200/-210) using Fe-based powders. The velocity fields are measured with the Laser Doppler Anemometry (LDA). Additionally, resulting coatings are analyzed metallographically with regard to their properties and a correlation with the particle in-flight properties is given. The experimental work is accompanied by computational fluid dynamics (CFD) simulations of spray jet and particle velocities, leading to a comprehensive analysis and characterization of the achievable particle properties with state-of-the-art HVOF and APS systems.

Within the High Velocity Oxygen Fuel Process (HVOF-Process) various fuels can be used to provide the needed thermal and kinetic energy such as ethene, propane, methane or kerosene. Modelling the combustion in a HVOF-System poses a challenge concerning chemical kinetics of the kerosene reaction process. In this work a reduced reaction mechanism and a model describing chemical reactions as well as governing fluid dynamics are presented to simulate kerosene driven HVOF-Process. The kerosene combustion process within a HVOF-System usually takes place above temperatures of 2000 K, where some species dissociate. Therefore, accruing species have to be included in the reaction mechanism. The combustion process is described with a reduced reaction mechanism. The reaction rate is described by a finite rate model in form of Arrhenius. The gas flow is considered as a first phase and the kerosene droplets injected into the combustion chamber become a second phase. Afterwards simulation results are presented and discussed.