Wear-resistant cobalt-based coatings for injection moulds by cold spray

In this study, cold spray and high-velocity oxy fuel processes were respectively used in applying cobalt-based and nickel-based alloys on steel injection moulds. Effects of changes in the main cold spray deposition parameters and in powder composition of the cobalt-based alloy were optimised in terms of machinability and hardness improvements. A four-cavity mould was configured to allow the comparison of wear resistance between coated and heat-treated inserts in severe operating conditions. Real parts were produced by injection moulding, using a glass-fibre-reinforced polymer. Surface topography of the inserts was characterised in defined key-zones after polishing and at each scheduled stop of the moulding process. Experimental results showed that steel mould inserts coated by thermal spray and then polished can be a valid alternative to heat-treated steel for most applications.