Thermal processing is a critical step in the preparation of an enormous range of finished and intermediate goods, including automobile parts, aerospace, electronics, oil and gas, even pharmaceuticals. Few final products make it to market without having undergone some level of heat treatment during the development and manufacturing chain. General-purpose and specialized furnaces are now so ubiquitous that thermal processes arguably form the bedrock of industrial-scale manufacturing worldwide.

High-temperature alloys are essential to the plethora of furnace designs and heat treatment techniques that manufacturers now enjoy. Whether they are employed directly in furnace assemblies – from hot zones to the outer shell – or used as supplementary parts like boats, trays and carriers, high-temperature alloys provide superior mechanical properties at severe operating temperatures.

Which High Temp Alloys are Best Suited for Furnaces?

Refractories like molybdenum (Mo), niobium (Nb), tantalum (Ta), and tungsten (W) offer superb temperature performance, retaining their characteristic mechanical qualities at temperatures exceeding 1000°C. These may be used in their pure formats in select instances, for example, electron beam melted (EBM) tantalum rods are often used for heating elements in hot zones with operating temperatures exceeding 1482°C. However, tantalum heating elements must be accompanied by tantalum-based shielding to prevent chemical contamination. Such a configuration cannot be used in a hydrogen atmosphere either.

This dynamic is typical of the furnace design process. Engineers must carefully balance thermodynamic stability with high-temperature performance and an array of additional performance parameters specific to various user objectives. Continuing with the example of heating elements; tungsten heater coils are ideal for extremely high thermal processes with the greatest melting point of the refractory metals group, but it should not be used in air atmospheres.

There is no simple answer to the question, which high-temperature alloys are best suited for furnace design, as the requirements of modern thermal processing are vast. The only correct response is to carefully diagnose the right alloy for the job on a bespoke basis.

High-Temperature Alloys from H.C. Starck Solutions

At H.C. Starck Solutions, we are committed to design and manufacturing excellence and enduring research and development (R&D) into product innovation. Our high-temperature alloys are comprised of high purity refractories with carefully selected additives to yield the greatest performance for specific user objectives. We design and supply furnace components and accessories to users in a broad market cross-section, leveraging our unprecedented refractory metals expertise in the fabrication of boats, furnace assemblies and racks, heating elements and shields, hot zones and more.

Though pure refractories are often employed in hot zones, insulation, and shielding, we offer a wide range of high-temperature alloys based on molybdenum, which can be utilized throughout various furnace types. These include:

  • Titanium-zirconium-molybdenum (TZM): With elevated strength and outstanding creep-resistant properties at high temperatures, TZM alloys can be used for various items of kiln furniture, including brackets and heating elements.
  • Molybdenum-tungsten (MoW): High-density MoW components are ideal for molten metal applications, specifically non-ferrous melts such as zinc.
  • Molybdenum-hafnium-carbide (MHC): With exceptional all-round thermodynamic properties, MHC is typically reserved for extrusion dies.
  • Molybdenum-lanthanum (MoLa): An oxide-dispersion strengthened high-temperature refractory alloy exploited for its outstanding dimensional stability and high strength characteristics for various fabrications in furnace design.

Engineers always have to be very careful when designing specific  furnace elements from refractory and non-refractory metals. The difference between the two is that refractories are not inhibited by the poor thermodynamic and chemical properties of non-refractories, hence their general superiority. Yet it is always important to compare the most important characteristics of each to determine the right metals for individual jobs.

If you have specific user parameters that you are working towards and would like to speak with an H.C. Starck Solutions representative about specific heat treatment solutions, simply contact us today. We are happy to field questions about our high-temperature alloys and customer-first services.