DEBACOAT PROJECT: LASER CLADDING OF WC REINFORCED NiCr ALLOY ON INNER WALLS OF EXTRUSION BARRELS

摘要

In polymer injection, the melted plastic fed along the screw causes high deterioration on the different machine components. As a consequence, the inner wall of the barrel is subjected to severe wear and corrosion mechanisms. To counterbalance this phenomenon existing in injection tools, barrels are coated by thick and hard coatings. The aim of this work is to use laser cladding technique to produce coatings of a NiCr matrix reinforced with WC particles inside the extrusion barrels. In order to optimize the deposition process, different aspects were studied. The effect of the size and shape of the carbide particles was researched, in order to select the best cladding powders for the final coatings. On the other hand, two effective methods to avoid stress concentration and cracks were used: the preheating of the barrels before and during the laser cladding process and the use of a softer buffer layer between the base metal and the hard layer. The coatings produced in this study were analysed by NDT, optical microscopy and microhardness tests. As a result of the present study, crack free coatings were produced with thickness of roughly a millimetre.