Protective coatings for high temperature applications, as present e.g. during cutting and milling operations, require excellent mechanical and thermal properties during work load. The Ti1 − xAlxN system is industrially well acknowledged as it covers some of these requirements, and even exhibits increasing hardness with increasing temperature in its cubic modification, known as age hardening. The thermally activated diffusion at high temperatures however enables for the formation of wurtzite AlN, which causes a rapid reduction of mechanical properties in Ti1 − xAlxN coatings. The present work investigates the possibility to increase the formation temperature of w-AlN due to Hf alloying up to 10 at.% at the metal sublattice of Ti1 − xAlxN films. Ab initio predictions on the phase stability and decomposition products of quaternary Ti1 − x − yAlxHfyN alloys, as well as the ternary Ti1 − xAlxN, Hf1 − xAlxN and Ti1 − zHfzN systems, facilitate the interpretation of the experimental findings. Vacuum annealing treatments from 600 to 1100 °C indicate that the isostructural decomposition, which is responsible for age hardening, of the Ti1 − x − yAlxHfyN films starts at lower temperatures than the ternary Ti1 − xAlxN coating. However, the formation of a dual phase structure of c-Ti1 − zHfzN (with z = y/(1 − x)) and w-AlN is shifted to ~ 200 °C higher temperatures, thus retaining a film hardness of ~ 40 GPa up to ~ 1100 °C, while the Hf free films reach the respective hardness maximum of ~ 38 GPa already at ~ 900 °C. Additional annealing experiments at 850 and 950 °C for 20 h indicate a substantial improvement of the oxidation resistance with increasing amount of Hf in Ti1 − x − yAlxHfyN.

In injection molding wear of components is pronounced in positions with high flow rates of melt. The platelet‐wear‐test is an established method for comparative assessment of wear resistance of tool materials in such regimes. Within this study three metal matrix composites: two hard metals and one powder metallurgical steel were investigated. Results show non‐linear wear rates with increasing amount of plastic melt processed. The reasons were found in the viscous dissipation, which is based on high volumetric flow rates and the small wear gap, leading to a temperature rise, which are detrimental especially for the PM‐steel. Analysis of the processed glass fiber‐filled polymer showed dramatic decrease of fiber length due to the processing through the wear gap. This entails a high amount of free fiber ends, resulting in higher load for the surfaces through micro chipping. POLYM. ENG. SCI., 59:E302–E311, 2019. © 2018 The Authors. Polymer Engineering & Science published by Wiley Periodicals, Inc. on behalf of Society of Plastics Engineers.

Fiber‐reinforced polymers allow for the implementation of plastic materials in structural components. However, increasing incorporation of fibers up to 50 wt% causes accelerated component wear in injection molding machines. In particular, the barrel and screw in the compression zone suffer from increased wear. The abrasive fibers of the compacted polymer pellets in the solid bed protrude from the surfaces of the resin having an abrasive, brush‐like behavior. A modified pin‐on‐disk testing system with specially designed polymer pins was used to emulate the described tribological system in laboratory scale. Through varying contact pressure, temperature, and surface modifications of the counterparts (blank or coated powder‐metallurgical steel), abrasive wear as observed in industrial‐sized extruder screws could be successfully simulated on a laboratory‐scale testing system. Detailed investigations of the pins and disks highlighted that the glass fibers plow and cut the surface leading to abrasion as observed in the real field application. Temperature has been proven to be the most decisive driving force. Surface modifications such as protective physical vapor‐deposited CrN coatings are effective against abrasive wear, clearly outperforming untreated steels. The presented pin‐on‐disk‐test setup will improve screening of materials for extruders, thus enhancing the durability of injection molding machines. POLYM. ENG. SCI., 60:78–85, 2020. © 2019 Society of Plastics Engineers

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