Microstructure Study of Nickel-Based Superalloys after Deep Cold Rolling

Abstract:

Mechanical surface treatments are conducted on aerospace components in order to improve their fatigue life through inducing compressive residual stresses, cold work and smoother surface finish. The microstructures of the component surface and subsurface after treatment influence the crack nucleation and crack propagation significantly. This paper studies the effect of Deep Cold Rolling (DCR), a subsurface process using hydrostatically controlled balls, on the resulting microstructure of RR1000, a nickel-based superalloy used in high temperature aerospace applications. In this study, DCR of RR1000 was conducted by varying the diameter of the roller ball with a constant fluid pressure and overlap. Vickers microhardness was measured to characterize the work hardening behavior during DCR. The microstructure of RR1000 subsurface before and after DCR along both the rolling and transverse directions is analyzed further. The results show that deep cold rolling results in a significant variation on the microstructure of RR1000 including elongation of matrix grains and the precipitates, within a depth of 10 μm from the rolling surface. The change in microstructure along the rolling surface is found to be more prominent than along the transverse directions irrespective of the ball diameter.

• Periodical: Materials Science Forum (Volume 879)
• Pages: 169-174
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.879.169
• Online since: November 2016
• Authors: Balasubramanian Nagarajan*, Sylvie Castagne
• Keywords: Deep Cold Rolling, Mechanical Surface Treatment, Nickel Based Superalloy, RR1000

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