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What Is Thermal Cycling?

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  • Written By: Paul Scott
  • Edited By: R. Halprin
  • Last Modified Date: 25 August 2014
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Thermal cycling is a manufacturing process of alternatively cooling and heating material to enhance its strength and performance. This process induces what is known as molecular reorganization, optimizing a material's molecular structure and making it denser and more uniform. Most microscopic manufacturing defects such as fissures and pockets are removed during this process, thereby improving longevity and stress bearing qualities. Metal parts subjected to thermal cycling treatments are also less prone to suffer metal fatigue failures caused by internal corrosion and vibration. External corrosion resistance is also improved as are post-production processes such as brazing and plating when thermal cycling treatments are applied.

Although thermal cycling is a process which is effective on a number of different types of materials including composites, ceramics, and plastics, it is most commonly associated with its beneficial effect on metal parts. Most cast, forged, or machined metal parts feature numerous microscopic flaws such as fine cracks or fissures as well as intermolecular pockets. Although generally too small to be viewed with the naked eye, these imperfections are a common source of part failures due to vibrational or impact stress breaks and metal fatigue caused by internal corrosion. One of the most effective ways of removing a significant number of these flaws is the thermal cycling process. This process involves cooling or, less commonly, heating the part repeatedly, and then allowing it to return to ambient temperature.

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Also known as advanced cryogenics, the temperature modulation process has the effect of tightening or setting the molecular structure of the part and removing many, if not all, of its microscopic flaws. The absence of internal cavities and cracks minimizes the chance of internal corrosion developing, thereby giving the part enhanced stress handling and service life qualities. An additional benefit of denser, more uniform crystalline structures in a metal part is the removal of uneven heating areas or hot spots which ensures optimal cooling characteristics. The removal of internal flaws also makes the part more resistant to vibration and sympathetic resonance which further enhances resistance to metal fatigue.

The benefits of the thermal cycling process do not end there though; a treated part exhibits better surface characteristics as well. This, in turn, means the part is less likely to suffer surface corrosion, and finishes such as plating which are applied prior to thermal cycling adhere better and last longer. The same applies to any silver soldering and brazing carried out prior to cycling which also benefit from the thermal modulation process.

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