Mitigation of stress corrosion and fatigue by surface conditioning

a surface conditioning and stress corrosion technology, applied in the direction of flexible wheel, grinding machine components, manufacturing tools, etc., can solve the problems of re-freshing degraded surfaces, micro-structural, micro-chemical, or micro-geometrical susceptibility, and conventional peening methods do nothing to remove existing degraded surface conditions

Inactive Publication Date: 2009-01-29
GENERAL ELECTRIC CO
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Benefits of technology

[0007]It has now been discovered, surprisingly, according to the present invention, that it is possible to effect surface conditioning of a metal surface by rubbing the metal surface with a surface conditioning means comprising a plurality of abrasive bristles. The stretching action of the abrasive in the bristles on the metal surface during the rubbing causes tensile stress reduction in the metal surface.
[0008]In one aspect there is provided a method of conditioning a metal surface, comprising rubbing the metal surface with a

Problems solved by technology

Conventional peening and burnishing processes, including water-jet peening, laser shock peening, shot peening, hammer peening, and roller or ball burnishing, are known to locally reduce surface stresses, but do not reduce the micro-structural, micro-chemical, or micro-geometrical susceptibility of the material surface, and do not refresh degraded surfaces due to abusive fabrication practices or to service in an aggressive environment.
Conventional peening methods do nothing to remove existing degraded surface conditions, such as from frequently abusive fabricatio

Method used

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  • Mitigation of stress corrosion and fatigue by surface conditioning
  • Mitigation of stress corrosion and fatigue by surface conditioning
  • Mitigation of stress corrosion and fatigue by surface conditioning

Examples

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example 1

[0087]Referring to FIG. 21, there is shown a perspective view of a vessel penetration mockup block 80 for surface improvement evaluation in 0.6 inch diameter machine bore (Inconel 600 base material). The results are discussed below.

[0088]FIG. 22 shows residual stress depth profile measurements before surface improvement (baseline condition) in 0.6 inch diameter bore (Inconel 600 base material). FIG. 23 shows the residual stress depth profile measurements after surface improvement using a flexible hone abrasive in 0.6 inch diameter bore, and FIG. 24 shows the residual stress depth profile measurements after surface improvement using a flexible abrasive brush in 0.6 inch diameter bore.

example 2

[0089]FIGS. 25a, b, c, d and e show perspective views of a full size mockup of a PWR vessel bottom head instrument housing penetration attachment weld 82. The mockup was completed on one side with SCC-susceptible Inconel 132 (see Figures b and c) and on the other side with SCC-susceptible Inconel 182 (see Figures d and e), each joined to an Inconel housing stub. Half of each weld was measured for residual stress in the as-welded condition and the other half was measured in the surface improved condition.

[0090]FIG. 26 shows the residual stress depth profile before surface improvement using flexible brush abrasive (measurements made on outside diameter of the vessel penetration attachment weld mockup, Inconel 600 base material, Inconel 182 weld material). FIG. 27 shows the residual stress depth profile before surface improvement using flexible brush abrasive (measurements made on outside diameter of the vessel penetration attachment weld mockup, Inconel 600 base material, Inconel 132 ...

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Abstract

Method and apparatus for surface conditioning a metal surface typically having irregular surface contours, by rubbing the metal surface with a surface conditioning device having a plurality of bristles which contact the metal surface during the rubbing and effect tensile stress reduction or degraded layer removal in the metal surface.

Description

[0001]The present invention relates to a method and apparatus for providing mitigation of stress-corrosion cracking (SCC) and fatigue initiation in metallic components, including for example base metals and welds in austenitic stainless steels and nickel-base alloys. In particular, the invention provides a method and apparatus for mechanical surface conditioning of metals to mitigate susceptibility to crack initiation or growth of small cracks due to tensile surface stresses.BACKGROUND OF THE INVENTION[0002]Stress-corrosion cracking (SCC) in metals is generally known to be caused by the simultaneous presence of a susceptible material, an aggressive environment, and tensile stresses. In the past, mitigation of SCC has focused on reducing or eliminating one or more of these causes, either in the bulk state or locally at the exposed work surface.[0003]Conventional peening and burnishing processes, including water-jet peening, laser shock peening, shot peening, hammer peening, and rolle...

Claims

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Application Information

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IPC IPC(8): B24B1/00B24B7/00B24B41/00
CPCB24D13/10B24D13/20B24D13/145
Inventor OFFER, HENRY PETERSANDUSKY, DAVID WESLEYPAO, HSUEH-WEN
Owner GENERAL ELECTRIC CO
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