Turnbull, A.; Crocker, L.; Zhou, S. (2018) Do corrosion pits eliminate the benefit of shot-peening? International Journal of Fatigue, 116. pp. 439-447. ISSN 01421123

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Abstract

The impact of corrosion pits on the beneficial effect of shot-peening of 12Cr steam turbine blade steel has been evaluated under fatigue loading conditions in air. The fatigue limit was measured for pits of depth in the range 50 µm to 300 µm, typical of depths to be expected in a reasonably well-managed operating plant but with occasional transient excursions in water chemistry. XRD measurements indicated that the compressive residual stress approached zero at a depth of about 250 µm, yet a significant benefit of this residual stress on the fatigue limit was still retained with the pit of depth 300 µm. An explanation could be found in finite element analysis, which predicted a reduced net tensile stress range and mean stress at the base of the pit in the shot-peened specimen. The fatigue crack growth rate from a corrosion pit was also reduced by the residual stress, until the crack attained a depth of 0.9 mm, with the crack shape indicating constraint to lateral crack propagation near the surface.

Item Type:	Article
Keywords:	pitting, fatigue, shot peening, finite element
Subjects:	Advanced Materials > Corrosion
Divisions:	Engineering, Materials & Electrical Science
Identification number/DOI:	10.1016/j.ijfatigue.2018.07.004
Last Modified:	13 Dec 2018 15:08
URI:	http://eprintspublications.npl.co.uk/id/eprint/8186

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