Engineering special purpose components requires careful consideration of material class plus basic manufacturing processes. This is sometimes referred to as finding the appropriate process—material combination to yield parts with the right geometry, shape, size, and other key performance properties.
An Age-Old Process—Material Combination: Isothermal Forging
For example: High-strength near net super alloy shapes are often fabricated through isothermal forging. This closed-die hot working process provides a high level of control over the part deformation behaviour and microstructural evolution, ultimately translating to greater quality finished components. Isothermal forging is used to fabricate parts from super alloys and materials with low forgeability by maintaining the work piece at its maximum elevated temperature throughout the entire process. This can incur high equipment costs as dies are routinely heated to the temperature of the starting workpiece to eliminate cooling and maximise control of the metal’s flow characteristics.
Isothermal forging of superalloys is an ideal process—material combination for a wide range of applications, particularly for engineering parts intended for use in aerospace and defense markets. This is because forging dies offer the ability to fabricate high-strength profiles with fairly complex geometries at high throughput.
What Causes Forging Dies to Fail?
The long-term benefits of forging dies are dependent upon the tool life expectancy. Forging dies fail for numerous reasons, including abrasion to out-of-tolerance conditions, heat checking and spalling, thermal softening, excessive grinding, catastrophic failure, and more.
Wear-out of forging dies is a common issue that can often be readily repaired. However, accelerated wearing and unpredictable failures such as heat-induced fracture can be extremely disruptive to workflows. Even if they aren’t considered catastrophic failures, these issues can cause forging lines to fall off schedule due to increase scrappage and reworking of out-of-tolerance parts.
Even with rigorous maintenance schedules and exceptional process monitoring, all high-alloy forging dies will eventually wear out and will need to be replaced. This could be easily managed, but tool life is not an easy property to accurately predict. The best solution is to choose a forging die material that is inherently impact- and wear-resistant with excellent high-temperature strength.
High-Performance Molybdenum Forging Dies
At H.C. Starck Solutions, we supply high-performance molybdenum blanks for isothermal forging applications. With over 25 years’ experience supplying forging components to industry professionals around the world, we intuitively understand the pain points of isothermal forging and have endeavoured to supply value-added solutions to engineers in the aerospace and defense sectors.
Molybdenum is our first-choice solution for isothermal forging die applications owing to its high thermal conductivity, low thermal expansion, and enviable mechanical strength at high working temperatures. But these properties can be improved using select alloying additives.
Titanium-Zirconium-Molybdenum (TZM) Alloy
Our TZM alloy (0.50 Ti, 0.08 Zr, Bal Mo) benefits from increased strength and creep resistance at high temperatures, courtesy of titanium and zirconium carbides within the alloy matrix. It enhances the long-term strength of molybdenum significantly and enables longer services forging dies.
Molybdenum-Hafnium-Carbide (MHC) Alloy
Our MHC alloy is comprised of molybdenum and hafnium carbide. This is consolidated through a proprietary powder metallurgy process, yielding a finished part with high recrystallization temperatures, excellent strength, low rates of thermal expansion, and high thermal conductivity. This makes it ideal for forging die applications.
Want to learn more? Contact a member of the H.C. Starck Solutions team today for more information about our molybdendum alloys for forging dies.