For the last few years, the HVAF process has been established as a commercially used process and has gained an increasing share in the market of thermal spraying. The main thermal spray materials being used for HVAF spraying have been those based on the tungsten carbide family. Economical aspects and European regulations on chemicals management REACH (Registration, Evaluation and Authorisation of Chemicals) have motivated the demand for thinner WC based coatings, which are still dense and wear resistant. This demand has progressively increased, and the trend shows a further growth in the need for thermal spray feedstock for HVAF sprayed net shape coatings. The challenge for powder producers lies in providing suitable spray powders, with high and consistent quality as well as in considerable volume, to be able to make reliable recommendations to the users of HVAF technology. A deeper understanding of powder requirements for net shape coatings, matching the needs with new powder solutions, and appreciation of the differences in behavior or performance depending on powder type are essential to address the above challenges and constitutes the theme of this paper.

Additive manufacturing with metal powders enables a high degree of design diversity and an enormous material flexibility for components. The development of new products using special alloys requires just a small amount of powder. Therefore, a wire arc spraying process using nitrogen is applied for powder production by atomizing. The remaining oxygen content, the nitrogen temperature and pressure in the atomizing chamber are monitored to ensure consistent quality. The power source enables direct current (DC) and alternating current (AC). Further parameters like basic current Iground, pulse current Ipulse, pulse duration tpulse, impulse frequency fpulse and alternating current frequency fAC can be varied. On the process side, the following parameters are recorded during the tests: current, voltage, wire feed speed and flow rate of the atomizing gas as well as oxygen content and temperature inside the spray chamber. These parameters have an influence on particle size and composition. The aim is to influence the melting behavior by electrical and other process parameters. The investigations are carried out on solid wires made of an iron-based alloy EN ISO 14341-A: G42 4 M21/2 C1 3 Si1, AWS A 5.18: ER 70-6.

This paper addresses a need for information on nanoparticle emissions and related issues such as worker exposure, filtration efficiency, and dustiness. A survey has been conducted on the working conditions and safety measures used in thermal spray companies and the results compared to scientific literature and previous surveys. Responses to questions on matters of health and safety reveal a lack of information and awareness of the risks posed by the emissions of ultrafine particles generated by thermal spraying processes.

This study assesses the quality of flame-sprayed alumina coatings produced from recently developed alumina cord using argon and compressed air as atomizing gases. Coatings of different thicknesses were deposited on aluminum substrates and then analyzed using optical microscopy, X-ray diffraction, and resistivity measurements. The coatings, particularly those sprayed with argon, had fine microstructure and higher surface and volume resistivity than flame-spray coatings made from alumina cord in the past. They were also found to have higher alpha phase content than plasma-sprayed coatings, regardless of the atomizing gas used. The effect of humidity and the possible formation of aluminum hydroxides are also addressed.

Wire atomization processes used to make refractory and high temperature alloy powders are relatively expensive due to the cost of feedstock, energy, and gas. A new process based on Transferred Arc Wire Atomization technology, however, has the potential to overcome these problems. This paper introduces the innovative process which, in combination with hydrogen generation, presents new opportunities for several alloys that can be more easily processed by plasma wire atomization. The new approach shows promise to reduce both fixed and variable costs for certain refractory and high temperature materials.