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07421 Fabricating Nickel Alloy Products to Avoid Stress Relaxation Cracking

Picture for 07421 Fabricating Nickel Alloy Products to Avoid Stress Relaxation Cracking
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Various alloys subjected various heat treatments were examined in-service and tested to determine their susceptibility to stress relaxation cracking.

Product Number: 51300-07421-SG
ISBN: 07421 2007 CP
Author: Lewis E. Shoemaker, Gaylord D. Smith, Brian A. Baker, and Jon Poole
Publication Date: 2007
Industry: Materials Selection and Design
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Nickel-chromium alloys for service at elevated temperatures are generally solution annealed prior to service to coarsen their grain size to enhance their high temperature strength and resistance to creep and rupture. Alloys for high temperature are often supplied from the producing mill as solution annealed. However, this large grain condition is not optimum for fabrication as it can compromise weldability and the large grain material is subject to stress relaxation cracking when annealed after heavy cold forming. Ideally these alloys are supplied after a lower temperature heat treatment that anneals the product but avoids substantial grain growth. Such fine grain material is more readily formed and much more resistant to stress relaxation cracking when solution annealed after forming. While the example of alloy 800HT is used to demonstrate the advantage of this processing sequence, the technique can be applied to essentially any alloy or stainless steel that is to be used for applications at highly elevated temperatures.

Key Words: Alloy 800HT, UNS N08811, Alloy 800H, UNS N08810, Alloy 617, UNS N06617, Alloy 601, UNS N06601, Cracking, Fabrication, Welding, Heat Treatment, Annealing, Stress Relaxation, Pipe, Strain-Age Cracking, SAGBO

 

Nickel-chromium alloys for service at elevated temperatures are generally solution annealed prior to service to coarsen their grain size to enhance their high temperature strength and resistance to creep and rupture. Alloys for high temperature are often supplied from the producing mill as solution annealed. However, this large grain condition is not optimum for fabrication as it can compromise weldability and the large grain material is subject to stress relaxation cracking when annealed after heavy cold forming. Ideally these alloys are supplied after a lower temperature heat treatment that anneals the product but avoids substantial grain growth. Such fine grain material is more readily formed and much more resistant to stress relaxation cracking when solution annealed after forming. While the example of alloy 800HT is used to demonstrate the advantage of this processing sequence, the technique can be applied to essentially any alloy or stainless steel that is to be used for applications at highly elevated temperatures.

Key Words: Alloy 800HT, UNS N08811, Alloy 800H, UNS N08810, Alloy 617, UNS N06617, Alloy 601, UNS N06601, Cracking, Fabrication, Welding, Heat Treatment, Annealing, Stress Relaxation, Pipe, Strain-Age Cracking, SAGBO

 

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07423 Control of Relaxation Cracking in Austenitic High Temperature Components

Product Number: 51300-07423-SG
ISBN: 07423 2007 CP
Author: Hans Van Wortel
Publication Date: 2007
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The research was focused to assess the key factors concerning relaxation cracking and how to control it. It included the effect of chemical composition of the base materials (both Fe and Ni base alloys), heat to heat variation, grain size, cold deformation, welding, operating temperature and heat treatments.
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51318-11046-The investigation of Incoloy 800H Relaxation Crack Mechanisms

Product Number: 51318-11046-SG
Author: Yunjo Ro / Ihho Park / Gyutae Park / Jaewoong Kim
Publication Date: 2018
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In the present study, detailed microstructure of the crack-tip region of a failed tube was examined using SEM, TEM and EBSD to clarify the relaxation crack mechanism.  Details of the microstructural findings and a proposed mechanism of stress relief cracking will be discussed.

 
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08454 Stress Relaxation Cracking Of Welded Joints In Thick Sections Of Type-347 Stabilized Grade Of Stainless Steel

Product Number: 51300-08454-SG
ISBN: 08454 2008 CP
Author: Christian E. van der Westhuizen
Publication Date: 2008
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This paper discusses reactors in hydrocarbon service that experienced numerous cracking problems over a 8-year period, where cracks were confined to the welded zones.  The material is  TP347 stainless steel, welded with E347-16 consumables.
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