MEJORAMIENTO DE LA EFICIENCIA DE LOS MOLDES DE INYECCIÓN MEDIANTE LA APLICACION DE RECUBRIMIENTOS DE CrN/TiN

Abstract

The injection molding process for polymer manufacturing requires mirror finish mould surfaces for the fabrication of a lot of products. A problem is the adherence of the injected products to the core, which negatively affects the product  quality.  This fact  leads  to  expensive  inserts mould  fabrication,  which can represent up to 20% of the productivity costs. Other disadvantage is the wear of many mould parts. An alternative to reduce mould wear and product adherence is the application of hard coatings. Thereby CrN/TiN hard coatings with 10, 40, 80 and 100 bilayers were deposited on AISI H13 steel samples, which are widely utilized for injection moulds fabrication. The deposition technique was the magnetron sputtering. For all cases the total thickness of the coating was approximately 4 µm. Properties like hardness, adherence, wear resistance and phase composition were evaluated by microindentation measurements, scratch test, micro wear test and X- ray diffraction, respectively. An enhancement of the coated sample’s properties was observed with the increase of the bilayer number, so that an improvement of around 70% was obtained for the samples coated with 100 bilayers compared to the uncoated ones. Finally, two coated injection moulds and four slide plates are been evaluated at Industrias ESTRA S.A. Company in Medellín City, without failure after 3 months of the tools operation.