Oxford team lends Hong Kong a hand in toughening injection mould coatings

Researchers in materials science and engineering at the university have developed the new anti-sticking coatings, which they believe could reduce mould tool downtime during production. They feature high corrosion resistance, low friction coefficient, high wear resistance, high temperature resistance, and anti-sticking  epoxy moulding compound.

The work started out with electronic packaging industry but the technology can be easily extended to other areas, said Dr Kwok Yan Li, who is on sabbatical to George Washington University in Virginia, US. Dr Li, who trained in mechanical engineering at Birmingham University in the UK, developed the coatings in Hong Kong with a team of eight researchers.

Isis, the arm of Oxford University that licenses patents for commercial exploitation, is hoping to find partners to develop the coatings, which modify existing coatings of CrN (chromium nitride) with Ni (nickel), to toughen them up. A Japanese firm is believed to be interested in the technology.

Dr Li said injection mould tools typically had to be cleaned after a number of operations which depends on the operation and moulding compound used.  This required machine downtime and the use of cleaning agents. “We want to reduce the number of mould releasing agents used,” he told The Engineer. He said this would help reducing the necessary cleaning cost of products.

“Isis came to us interested in commercialising the technology,” he added.

The research group has successfully fabricated the Cr-Ni-N films with different compositions by varying bias, target power, gas flow rate and so on. Within the mixed phases of the composition and structure of fcc-CrN, hcp-Cr₂N and metallic Ni, the content of Ni in the Ni-Cr-N coating system is between 0-64%, with oxygen < 2%. The incorporation of Ni toughened the composite coatings.