Diamond coatings on 3D structured steel

Abstract

This paper reports on advancements in micromoulding tool inserts. Different surface coatings were used and their influence was observed in what concerns part dimensional stability and subsequent polymer finishing quality. A set of thermoplastic injection moulding inserts with a simple 3D structured feature and different surface treatments were used to produce HDPE moulded parts. Surface treatments employed included the deposition of two different types of CVD diamond coatings on steel substrates using CrN interlayers and a commercially used CrN. Finally, a bare steel insert was used as a reference sample in order to monitor the influence of the coatings. The as-deposited diamond displayed good quality polycrystalline diamond surface. After 500 injection cycles, the surface of the inserts did not show any signs of detectable degradation. The moulded objects with the diamond coating demonstrated superior dimensional performance, nevertheless, the coated samples displayed a more tarnished surface than those obtained using bare steel or the CrN finished inserts.