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CRM had previously developed the jet vapour deposition (JVD) concept to evaporate metals on steel strip. In this research two new concepts were developed to mix vapours. - The 'dual JVD' based on two separate JVD's collecting vapours in one making chamber. However, it was not possible in this system to prevent fluctuation of the alloy across the strip width. - The 'twin JVD' based on two co-focal JVD systems (without mixing chamber). The heat of condensation induced some inter-diffusion of the two metals. Without additional post-diffusion treatment, the coating was characterised by a compact multi-layer structure. The concept of JVD with graphite crucibles was confirmed for Zn, Mg, Zn-Mg alloy and copper. Graphite reacts with more reactive metals (Cr, Mn and AI) to dramatically reduce the evaporation rate. Various coatings were applied to improve the crucible lifetime but more developments are still necessary to fulfil industrial requirements. This research out-lined the importance of thermal pattern on projection efficiency. A wide evaporator (700 mm) was designed, constructed and successfully tested with less than 5 % thermal loss, 82 % electrical yield and more than 95 % metal efficiency. The Zn-Mg alloys produced gave outstanding corrosion resistance and friction behaviour. Continuous annealing is a proper way to prepare the steel surface prior to JVD coating (no etching). The strip temperature at the exit of the annealing line improves Zn-Mg interdiffusion (no additional calorie costs). An economical evaluation was made for a 4µm Zn-Mg coating: integrated JVD line is EUR 12/t cheaper than a stand alone PVD line.

Additional information

Authors: SCHMITZ B, CRM - Centre de recherches métallurgiques, Angleur (BE);CHOQUET P, Arcelor (IRSID), Maizières-lès-Metz (FR);PETITJEAN J, Arcelor (Sollac-Ledepp), Florange (FR)
Bibliographic Reference: EUR 21783 EN (2005), 100 pp. Euro: 15
Availability: Katalogue Number: KI-NA-21783-EN-S The paper version can be ordered online and the PDF version downloaded at:
ISBN: ISBN: 92-894-9901-x
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