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No wear in the nozzle: TZM for plastic injection molding

No wear in the nozzle: TZM for plastic injection molding

Date posted: May 27, 2014 // Plansee

11/03/2014, Small quantities of titanium and zirconium improve the dimensional stability of molybdenum at high temperatures. But it is not only at temperatures above 1000 °C that the properties of the TZM alloy prove their worth.One important application is plastic injection molding.

Hot_runner_nozzlePlastic injection molding is a process used for the manufacture of plastic products. Liquid plastic is transported through a hot runner. This plastic is injected into a mold through the hot runner.

The nozzle material is subject to high levels of mechanical stress at temperatures of 400 °C. One critical factor is the plastic that is being used. Many types of plastics contain extremely hard additives such as glass fibers or pigments.

This means that the wear resistance of the nozzle material is of particular importance alongside good thermal conductivity to the tip of the nozzle.

To increase the lifetime and keep tooling times and downtimes to a minimum, Plansee uses the molybdenum alloy TZM to manufacture its hot runner nozzles. Plansee has developed this molybdenum alloy. Solid solution hardening of molybdenum and titanium coupled with titanium-zirconium carbides improve the mechanical properties at high temperatures. This is good for applications in high-temperature furnaces, but plastic injection molding is carried out at moderate temperatures in comparison.

But TZM also has its strengths here. The outstanding thermal conductivity and corrosion resistance of TZM compared with other materials offer decisive advantages for the hot runner process. Not only that, the hardness and tensile strength of the alloy are greater than that of pure molybdenum. This makes the material much more resilient.

HV10_Mo_TZM Tensile_strength

Surface hardening increases the service life of hot runner nozzles.

Wear resistance is particularly important when processing plastics that contain highly abrasive components. To extend the service life of hot runner nozzles even further, Plansee offers its own special surface hardening for its TZM nozzles. Unlike traditional PVD hard material coatings, which often have poor adhesion, the coating developed by Plansee is a well-bonded diffusion layer with a thickness of just 10 µm. In this way, Plansee increases the surface hardness up to 2,000 HV, thus ensuring good resistance to highly abrasive plastics. Components that are ready for use can be hardened without any impact on the dimensional tolerances.

As well as TZM, Plansee offers a wide range of other alloys based on molybdenum, tungsten, tantalum and niobium. Find out more about our materials and their fields of application.