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Micrographs showing different degrees of decarburization. (a) Total decarbu...

in Failures Related to Heat Treating Operations > Failure Analysis and Prevention
Published: 01 January 2002
Fig. 72 Micrographs showing different degrees of decarburization. (a) Total decarburization caused by a furnace leak during gas carburizing of AISI 1018 steel. 500×; 1% nital etch. (b) Partially decarburized specimen. 190×. Source: Ref 30 More
Book Chapter

Cracking in Carbon-Molybdenum Desulfurizer Welds

Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.chem.c0048835
EISBN: 978-1-62708-220-4
... by metallurgical examination of a cross section of a longitudinal crack. It was concluded that the damage was caused by a form of hydrogen attack. Installation of a used Cr-Mo steel vessel with a type 347 stainless steel weld overlay was suggested as a corrective action. Decarbuization Desulfurizer reactors...
Abstract
Welds in two CMo steel catalytic gas-oil desulfurizer reactors cracked under hydrogen pressure-temperature conditions that would not have been predicted by the June 1977 revision of the Nelson Curve for that material. Evidence of severe cracking was found in five weld-joint areas during examination of a naphtha desulfurizer by ultrasonic shear wave techniques. Defect indications were found in longitudinal and circumferential seam welds of the ASTM A204, grade A, steel sheet. The vessel was found to have a type 405 stainless steel liner for corrosion protection that was spot welded to the base metal and all vessel welds were found to be overlaid with type 309 stainless steel. Long longitudinal cracks in the weld metal, as well as transverse cracks were exposed after the weld overlay was ground off. A decarburized region on either side of the crack was revealed by metallurgical examination of a cross section of a longitudinal crack. It was concluded that the damage was caused by a form of hydrogen attack. Installation of a used Cr-Mo steel vessel with a type 347 stainless steel weld overlay was suggested as a corrective action.