Modified Nozzle for the Atmospheric Plasma Spraying
A modified Laval-like-contour for a convergent-divergent nozzle is presented for the Atmospheric Plasma Spraying (APS). The influence of the nozzle design on the thermal and deposition efficiency as well as on the arc voltage fluctuations and the sound level of the plasma torch are investigated and compared with former investigations [1, 2]. The improvements of the quality of DC-Plasma sprayed Al2O3 coatings by the nozzle design is shown by the coating porosity, adhesive and breakdown strength. A 2D-model presents the gas dynamics inside the nozzle. The intention of this study is to promote the industrial application of convergent-divergent nozzles for the APS in conjunction with the optimisation of the plasma gas dynamics.
A. Schwenk, G. Nutsch
Technische Universität Ilmenau, Germany
H. Gruner
MEDICOAT AG, Mägenwil, Switzerland
)Wear and corrosion resistant coatings on aluminium alloys obtained by thermal spraying
With the aim to elaborate a coating technology for improved wear resistance of AA2017 alloy surfaces Cr3C2/Ni20Cr 75/25 top coats and Ni5Al, Ni5Ti as well as Ni20Cr bond coats are produced. Bond coats are deposited by arc spraying as well as HVOF and top coats by HVOF only. Optimum spraying parameters are determined. The resulting adhesion of bond coats to AA2017 is in the order of 50 MPa. Microscopic investigations point at metallurgical reactions at interfaces both between bond and top coats and between bond coats and substrates. In oscillating wear tests on top coats with alumina balls as counterbody only the coatings are worn, while hardened 100Cr6 steel balls cause no wear of the coatings.
Krystian Butkiewicz, Witold Milewski, Lech Kwiatkowski Institute of Precision Mechanics, 01-796 Warsaw, Duchnicka Str. 3, Poland Bernhard Wielage, Andreas Wank, Hanna Pokhmurska
Institute of Composite Materials, Chemnitz University of Technology, 09107 Chemnitz, Germany
CGS sprayed filler coatings for brazing of light weight alloys
Application of cold gas spraying for deposition of braze filler coatings is investigated. Different light weight alloy substrates, i.e. aluminum AA1050, AA3005, AA5754 and AA7022, magnesium AZ91 and titanium TiAl6V4, are used. Filler coating materials depend on the substrate melting temperature. So for aluminum alloys Al12Si and zinc based fillers, for AZ91 pure zinc and for Ti6Al4V different Cu-Ni blends are applied. CGS process parameters are varied with regard to process gas (nitrogen) temperature and pressure, powder feed rate and spray distance. Correlation to process characteristics and economical aspects are given. The usability of the produced filler coatings is shown by different optimized brazing/soldering processes. In case of aluminum braze joints a full metallographical investigation is carried out by optical and scanning electron microscopy as well as EDXS analyses. The gathered results are compared with those of conventional filler material addition, i.e. wire, roll plating and foil.
B. Wielage, T. Grund, S. Ahrens, A. Wank, F. Trommer, Chemnitz / D
Thermally sprayed solder/braze filler alloys for the joining of light metals
Generally the established thermal spray technologies like flame or arc spraying can be used for the defined deposition of solder/braze filler metal layers. But for those processes used under atmospheric conditions the achieved quality of the solder/braze joints is low. A high density of defects like inclusions or oxides, pores and contaminations are not avoidable. The novel technique of the cold gas spraying (CGS) works with very low process temperatures. Therefore the heating of spray particles is reduced to a minimum. The produced coatings are free of oxides and show very low porosity. So investigations concerning the potential of CGS for the application of solder/braze filler metals are self-evident. In this work, substrates of different aluminium alloys (AA1050, AA3005, AA5754 and AA7022) are chosen. Depending on their particular solidification temperature, the used solder/braze filler materials are Al-, Zn- and Sn-based alloys.
B. Wielage, A. Wank, Th. Grund
Institute of Composite Materials, Faculty of Mechanical Engineering, TU Chemnitz