Advanced Residual Stress Analysis in Thermal Spray and Cold Spray Processes
- PDF / 1,201,850 Bytes
- 7 Pages / 595.276 x 790.866 pts Page_size
- 29 Downloads / 205 Views
GUEST EDITORIAL
Advanced Residual Stress Analysis in Thermal Spray and Cold Spray Processes
ASM International 2020
Vladimir Luzin
Seiji Kuroda
The theme of this special issue focuses on the studies and discussions of residual stress found in thermal spray and cold spray deposited microstructures. In bulk cast materials, it is normally accepted that the tensile residual stress will accelerate the initiation of surface cracks and their growth, therefore, significantly reducing the fatigue lifetime. In a different scenario, the phenomenon of stress corrosion cracking explicitly requires compressive surface residual stress to cause crack propagation and development leading to the overall failure of the material at its surface. The theoretical concepts provided in these two examples are applicable more broadly to coatings and deposits produced by thermal spray and cold spray; as well the papers in this special issue present case exemplars that demonstrate the influence of coating residual stress on the performance of components.
Shuo Yin
Andrew S.M. Ang
It is important to appreciate the unique and lamellar microstructure produced by thermal spraying or cold spraying of ‘splats’; typical microstructure features can include macro- and micro-porosity, as well as other defects (e.g. weak splat-to-splat interfaces with potential or actual cracking). Stresses will tend to concentrate at those defects, locally intensifying the average stress by a factor of three or higher. Thus, if the residual stress in a coating is tensile, this can be detrimental and lead to the failure of the coating prematurely in its service life or even failure of coating during spraying (Ref 1). This can manifest through the coating or deposit cracking, delamination, or spalling, and these occurrences are likely familiar to those who have practical experience in thermal spray or cold spray (see Fig. 1a).
123
J Therm Spray Tech
Why is Residual Stress in Thermal Spray and Cold Spray Materials Important? For thermal spray or cold spray coatings used in prime reliant applications, any risk of premature failure due to detrimental residual stress in the sprayed coating is maybe even more significant than the actual bulk component. Similarly, detrimental residual stress can also limit the volume of material that can be additively deposited by thermal spray or cold spray techniques for 3D printing applications without major defects overwhelming the process with flaws or warping. The realization of these limitations is perhaps the main motivation behind the collective academic efforts to provide a reliable framework to study residual stresses in sprayed coatings and deposits; initially by means of experimental and theoretical analyses, and later by finite element modelling approaches. The collection of articles found in the current special issue of the journal are good examples to demonstrate the important role of residual stress in its various aspects and applications. While the two earlier examples that were mentioned, namely fatigue fracture an
Data Loading...
