Researchers Strengthen Machines That Produce “Super Engineering Plastics”

A team of Japanese researchers came up with a new way to make machines that make super engineering plastics more resistant to wear and corrosion.

Industrial and automotive machinery, such as automotive engine parts, contain materials that are, heat-, wear-, and corrosion-resistant. They are known as “super engineering plastics,” and they continue to revolutionize manufacturing processes. While they are actually plastic, they are much stronger than the typical plastics we encounter in everyday life. These materials, however, create a corrosive environment during manufacturing.

That’s changing with a new innovation developed by a team of researchers based in Japan. They designed a new method to improve the wear and corrosion resistance of the machines that produce super engineering plastics. The researchers published their results on August 27, 2019, in npj Materials Degradation, a Nature journal.

Surface appearance of the developed steel containing copper (left) and copper-free counterpart (right). Credit: Kenta Yamanaka et al, Tohoku University

“The global market for super engineering plastics has grown in recent years because they have remarkably high-temperature resistance, good mechanical strength, and exceptional chemical and solvent resistance in high-temperature environments,” said Kenta Yamanaka, paper author and associate professor of deformation processing at the Institute for Materials Research at Tohoku University. “However, during the manufacturing process, the reciprocating screw in the manufacturing apparatus usually suffers from frequent wear loss because the semi-fluid raw materials commonly contain a large number of glass fibers as reinforcement.”

Super engineering plastics also decompose into sulfuric gas, inducing a highly corrosive environment in addition to the high physical wear conditions. The screws in the manufacturing machines cannot withstand such an environment for long.

To correct this issue, Yamanaka and the researchers studied a steel alloy known as high-speed steel, which is currently mainly used for tools. According to Yamanaka, the steel has outstanding mechanical properties at room and elevated temperatures, but it’s vulnerable to corrosion.

The researchers used an alloy based on high-speed steel and treated it with copper.

Screw for plastic injection molding, as fabricated with the developed steel. Credit: Kenta Yamanaka et al, Tohoku University

“The wear and corrosion resistance of steels generally show a trade-off relationship,” Yamanaka said. “In this study, we demonstrate that adding trace copper to high-hardness steels significantly improves the corrosion resistance of the alloys, resulting in an excellent combination of wear and corrosion resistance.”

After analyzing the alloy through imaging and experimental studies, the researchers found that they had successfully developed a highly wear and corrosion-resistant steel. Next, they plan to further investigate the alloy’s properties for application in other fields.

Reference: “Corrosion-resistant carbide-reinforced martensitic steel by Cu modification” by Chen Zhang, Kenta Yamanaka, Huakang Bian and Akihiko Chiba, 27 August 2019, npj Materials Degradation.
DOI: 10.1038/s41529-019-0092-3

This work was supported by the Adaptable and Seamless Technology Transfer Program through Target-Driven Research & Development from the Japan Science and Technology Agency and the ISIJ Research Promotion Grant from the Iron and Steel Institute of Japan.