Practical Failure Analysis

, Volume 2, Issue 4, pp 39–46 | Cite as

Alloy 430 ferritic stainless steel welds fail due to stress-corrosion cracking in heat-recovery steam generator

  • H. Krafft
Peer Reviewed Articles

Abstract

Alloy 430 stainless steel tube-to-header welds failed in a heat recovery steam generator (HRSG) within one year of commissioning. The HRSG was in a combined cycle, gas-fired, combustion turbine electric power plant. Alloy 430, a 17% chromium (Cr) ferritic stainless steel, was selected because of its resistance to chloride and sulfuric acid dewpoint corrosion under conditions potentially present in the HRSG low-pressure feedwater economizer. Intergranular corrosion and cracking were found in the weld metal and heat-affected zones (HAZs). The hardness in these regions was up to 35 HRC, and the weld had received a postweld heat treatment (PWHT). Metallographic examination revealed that the corroded areas contained undertempered martensite. Fully tempered weld areas with a hardness of 93 HRB were not attacked. No evidence of corrosion fatigue was found. Uneven temperature control during PWHT was the most likely cause of failure.

Keywords

alloy 430 alloy 439 ferritic stainless steel intergranular stress corrosion postweld heat treatment sensitization 

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Copyright information

© ASM International - The Materials Information Society 2002

Authors and Affiliations

  • H. Krafft
    • 1
  1. 1.Bechtel CorporationFrederick

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