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Additive Manufacturing Additive Manufacturing

Measuring the Thermal Conductivity of Powders for Additive Manufacturing and Powder Metallurgy Applications

Additive Manufacturing (AM) is the process in which an object or desired part is manufactured through the additive deposition of individual layers of material. AM processes pertaining to metals and ceramics include selective laser sintering, electron beam melting, and laser powder bed fusion. For plastics, these and other techniques such as extrusion may be employed. In all cases, a feedstock (typically a powder) is melted into the desired position in a localized manner using a heat source – which may be physical such as a heating element or arc of electricity, or may be a high energy beam such as a laser or electron beam. The localized melt is then allowed to re-solidify before the next layer is deposited. 

The thermodynamics of these processes are extremely complex, and are highly dependent on feedstock composition and quality, process chemistry, ambient atmosphere, deposition rate, and to some extent the part being machined. Therefore, AM process optimization can be challenging. Metals have additional challenges as it is often desirable to control the quenching of the metal to control the phase distribution in the alloy – particularly when working with shape-memory alloys. Ceramics tend to be relatively brittle and prone to thermal strain effects, so care must be taken not to allow too much of a thermal gradient to form in the material to avoid cracking of the finished part. Polymers require tight temperature control to ensure good quality of the finished part and to avoid things like density gradients forming in the work item.  

  • Components Made Through Additive Manufacturing Processes

    Components Made Through Additive Manufacturing Processes

  • Powder Blend with Unmixed Particles

    Powder Blend with Unmixed Particles

Why Is Thermal Conductivity Important?

Efficient optimization of these processes requires a thorough understanding of the thermophysical properties of the system and a consistent, well characterized powder feedstock. Thermal conductivity is particularly important in terms of modelling the thermal management of these processes and the cooling kinetics involved.  

How Do You Measure the Thermal Conductivity of Additive Manufacturing Feedstocks? 

To understand how quickly heat can be dissipated from the hot zone of an AM process, a thorough understanding of the thermal conductivity of the part, the melt, and the feedstock is needed. Thermal conductivity measurement provides this understandingC-Therm’s Trident offers MTPS for rapid and easy characterization of feedstock materials and parts, requiring only one sample of the material. Trident’s TPS anisotropic utility enables characterization of anisotropically deposited parts. Finally the TLS module enables testing of the melt phase of polymers, all on a single testing platform. This understanding can also benefit from a multi-technique approach – TGA and calorimetric techniques to understand thermal stability, heat capacity, and heats of phase change will aid in measuring the amount of heat that is absorbed and how quickly the materials will heat and cool. 

  • Trident is able to measure thermal conductivity using MPTS, TPS, and needle probe methods

    Trident is able to measure thermal conductivity using MPTS, TPS, and needle probe methods

  • MTPS sensor technology only requires one point of contact

    MTPS sensor technology only requires one point of contact

  • National Aeronautics and Space Administration (NASA)

    We purchased the C-Therm Thermal Conductivity Analyzer after seeing a demonstration of how fast and easy it is to operate. The instrument provides unequivocal results and provides the flexibility to test powders and liquids. In terms of our satisfaction with the purchase, I’d give it a 10 out of 10 - extremely satisfied.

    Dr. Enrique Jackson,
    Aerospace Polymeric Engineer

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  • University of Alicante (Spain)

    We have been using C-Therm for the last 10 years. During this period of time we have been able to analyse a great variety of materials due to the equipment's versatility: from solids to powders, liquids and pastes. This is a vital feature for us, as a central analysis service for researchers of our own university, other education and research institutions and companies in Spain and abroad.

    Dr. Ion Such Basáñez,
    Thermal Analysis and Porous Texture Characterization Unit

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Case Highlights

How Do You Use Thermal Effusivity in Powder Metallurgy and Powder Blending?
Powder blend

Figure 1. MTPS sensors can be applied in testing powder blend uniformity.

 

C-Therm’s MTPS thermal effusivity method can be applied in the testing of powders for blend uniformity monitoring.

Figure 2. Blending behavior can be unknown (left), stable (middle), or sensitive (right). Unerstanding of blending behavior is critical for good-quality test results.

  C-Therms MTPS method can be integrated into blenders can be applied in-line or at-line for blend uniformity testing in generation of feedstocks. By placing multiple sensors in different positions, thermophysical uniformity of the blend can be assured.  

Figure 3. Thermal effusivity in identifying regions of stable blend and de-mixing.

As seen in the image above, C-Therm’s MTPS sensors enable easy identification of regions of stable blend properties and de-mixing following over-blending.  

How Do You Measure the Thermal Conductivity of Finished Parts?

The MTPS sensor requires only an 18mm in diameter flat portion of the finished product to be able to measure the thermal conductivity. 

Modified Transient Plane Source Sensor testing thermal conductivity of reference ceramic.

SIMPLIFYING THERMAL CONDUCTIVITY

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