Abstract
It is well known that injection of glass fibre–reinforced plastics (GFRP) causes abrasive wear in moulds’ cavities and runners. Physical vapour deposition (PVD) coatings are intensively used to improve the wear resistance of different tools, also being one of the most promising ways to increase the moulds’ lifespan, mainly when used with plastics strongly reinforced with glass fibres. This work compares four different thin, hard coatings obtained using the PVD magnetron sputtering process: TiAlN, TiAlSiN, CrN/TiAlCrSiN and CrN/CrCN/DLC. The first two are monolayer coatings while the last ones are nanostructured and consist of multilayer systems. In order to carry out the corresponding tribological characterization, two different approaches were selected: A laboratorial method, using micro-abrasion wear tests based on a ball-cratering configuration, and an industrial mode, analysing the wear resistance of the coated samples when inserted in a plastic injection mould. As expected, the wear phenomena are not equivalent and the results between micro-abrasion and industrial tests are not similar due to the different means used to promote the abrasion. The best wear resistance performance in the laboratorial wear tests was attained by the TiAlN monolayer coating while the best performance in the industrial wear tests was obtained by the CrN/TiAlCrSiN nanostructured multilayer coating.
Highlights
Injection moulding is probably the most widely used plastics manufacturing technology.Nowadays, increasing requirements demanded by designers have driven the use of short glass fibers as reinforcements in many parts, namely for the automotive industry
The TiAlSiN film presented some aggregates at the surface, which can originate from tribological problems, both through the generation of preferred sites for crack nucleation and problems related to the release of these large particles in contact the counter-face
The results showed that the wear coefficient was the smallest for the TiAlN coating while it was the greatest for the CrN/TiAlCrSiN coating, corresponding to the better wear resistance (k−1) of the TiAlN coating, which presented a relatively low reduced Young’s modulus
Summary
Injection moulding is probably the most widely used plastics manufacturing technology.Nowadays, increasing requirements demanded by designers have driven the use of short glass fibers as reinforcements in many parts, namely for the automotive industry. Abrasion is a typical phenomenon in the plastic injection moulding process and it becomes even more important when plastics are reinforced with glass fibres [1,2,3,4,5]. New developments in the polymer industry led to the use of new polymer formulations and blends that are more and more aggressive to steel mould cavities due to gases generated into the mould, causing serious corrosion problems, which bring new challenges to the coatings research and industry [7] This problem is magnified by the temperature effect [8], and it is even more important
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