voestalpine eifeler Coatings provides state-of-the-art, Physical Vapor Deposition (PVD) coatings for a variety of applications including Die Casting. eifeler’s patented, two-stage process includes an initial hardening of the surface via Plasma/Ion Nitriding, followed by the application of a mono-layered PVD coating. Referred to as Duplex-TIGRAL®, this treatment creates a hard, wear resistant barrier that reduces or eliminates the effects of soldering, erosion and wear of the tool steel surface.
In die casting, melts of different alloys are injected with pressure into a die set and then solidified. Depending on the melt alloy, the dies are subjected to different high thermal and mechanical stresses.
Typical die failures
Die casting dies are exposed to severe thermal and mechanical cyclic loading, which puts high demands on the die material. Thus, there are some phenomena, which restrict die life.
- Thermal fatigue cracking: The most common die failure in die casting is thermal fatigue cracking. During the die casting process the dies are subjected to alternate heating and cooling leading to high thermal stresses. This gives rise to severe strains in the surface layer of the die, gradually leading to thermal fatigue cracks (known as “heat checking”). Factors influencing thermal fatigue are basic material properties, design, die manufacturing and heat treatment (surface treatment), production parameters and maintenance.
- Gross cracking: Gross cracking is a temporarily thermal and/or mechanical over loading of the die. It may lead to large cracks and even total failure of the die. Fractures influencing gross cracking are basic material properties, design, die manufacturing and heat treatment, production parameters and maintenance.
- Indentation: Indentation in the parting lines or cavity surface are a matter of production parameters and basic die material properties.
- Corrosion: In cases where the cavity surface lacks a protective layer, the cast metal will diffuse into the die surface. At the same time, alloying elements within the die, will diffuse from the die surface into the cast metal. These processes can create both dissolution of the steel and intermetallic compounds between the cast metal and the die surface. In cases where severe formation of intermetallic compounds occurs, the cast metal will solder to the die surface. Factors influencing corrosion are production parameters, die design and surface treatment.
- Erosion: This is a form of hot mechanical wear on the die surface, often in and near the gating area. Erosion depends to a high degree on production parameters and die design. Most commonly a combination of corrosion and erosion damages occur on the die surface.
Die material properties
For the best die performance, the following basic die steel values and properties should be high and good:
- Hot yield strength
- Temper resistance
- Creep strength