Failure analysis of a 2.25Cr-1Mo-0.25V steel heavy wall-thickness multi-pass welded component

Pekka Nevasmaa, Sanni Yli-Olli, Olli Kortelainen, Arto Kiiski

Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientificpeer-review

Abstract

Crack-like defects were found in a low-alloy 2.25Cr-1Mo-0.25V steel multipass welded heavy wallthickness component prior to its usage. After welding, the component had been subjected to local Intermediate Stress Relief (ISR) heat treatment at 600-650°C, with the aim at removing diffusible hydrogen and enhancing partial tempering of the weldment microstructure before the final PWHT. The objective of the present paper was to investigate the actual fracture micromechanism of the discovered damage associated with the manufacturing stage of the component, in order to explain the inherent causes of failure. The metallographic and fractographic studies demonstrated (i) cracks propagating through the weld solidification structure as quasi-cleavage fractures, (ii) the presence of micro-cracks at thereby 'opened' solidification boundaries, as well as (iii) occasional appearance of ductile 'ridges' at the fracture surface; all that were characteristic of hydrogen-induced cold cracking. In line with this, Vickers hardness measurements revealed maximum hardness as great as 381-382 HV and 371-378 HV in cases of the CGHAZ and weld metal microstructures, respectively. Furthermore, hardness traverses in the weld thickness direction revealed higher hardness values in the weld intermediate thickness than closer to the surface or the root, which was ascribed to inadequacy of the thermal effects of the ISR heat treatment. The occurrence of hydrogen cracking was attributed to simultaneous co-existence of several adverse factors: (i) excessively high weldment hardness, (ii) accidentally high initial hydrogen content of the applied SMAW electrode and (iii) inherently high structural rigidity and restraint of the component.
Original languageEnglish
Title of host publicationBaltica X
Subtitle of host publicationInternational Conference on Life Management and Maintenance for Power Plants
EditorsPertti Auerkari
Place of PublicationEspoo
PublisherVTT Technical Research Centre of Finland
Number of pages12
ISBN (Electronic)978-951-38-8436-9, 978-951-38-8435-2
Publication statusPublished - 2016
MoE publication typeA4 Article in a conference publication
EventBALTICA X - International Conference on Life Management and Maintenance for Power Plants - Cruise, Helsinki-Stockholm, Finland
Duration: 7 Jun 20169 Jun 2016

Publication series

NameVTT Technology
PublisherVTT
Volume261
ISSN (Electronic)2242-122X

Conference

ConferenceBALTICA X - International Conference on Life Management and Maintenance for Power Plants
Abbreviated titleBaltica X
CountryFinland
CityHelsinki-Stockholm
Period7/06/169/06/16

Fingerprint

Failure analysis
Welds
Hardness
Hydrogen
Stress relief
Steel
Cracks
Solidification
Heat treatment
Microstructure
Vickers hardness
Tempering
Rigidity
Thermal effects
Welding
Defects
Electrodes
Metals

Cite this

Nevasmaa, P., Yli-Olli, S., Kortelainen, O., & Kiiski, A. (2016). Failure analysis of a 2.25Cr-1Mo-0.25V steel heavy wall-thickness multi-pass welded component. In P. Auerkari (Ed.), Baltica X: International Conference on Life Management and Maintenance for Power Plants Espoo: VTT Technical Research Centre of Finland. VTT Technology, Vol.. 261
Nevasmaa, Pekka ; Yli-Olli, Sanni ; Kortelainen, Olli ; Kiiski, Arto. / Failure analysis of a 2.25Cr-1Mo-0.25V steel heavy wall-thickness multi-pass welded component. Baltica X: International Conference on Life Management and Maintenance for Power Plants. editor / Pertti Auerkari. Espoo : VTT Technical Research Centre of Finland, 2016. (VTT Technology, Vol. 261).
@inproceedings{048754b070604b989f01ac2a60f1d3e3,
title = "Failure analysis of a 2.25Cr-1Mo-0.25V steel heavy wall-thickness multi-pass welded component",
abstract = "Crack-like defects were found in a low-alloy 2.25Cr-1Mo-0.25V steel multipass welded heavy wallthickness component prior to its usage. After welding, the component had been subjected to local Intermediate Stress Relief (ISR) heat treatment at 600-650°C, with the aim at removing diffusible hydrogen and enhancing partial tempering of the weldment microstructure before the final PWHT. The objective of the present paper was to investigate the actual fracture micromechanism of the discovered damage associated with the manufacturing stage of the component, in order to explain the inherent causes of failure. The metallographic and fractographic studies demonstrated (i) cracks propagating through the weld solidification structure as quasi-cleavage fractures, (ii) the presence of micro-cracks at thereby 'opened' solidification boundaries, as well as (iii) occasional appearance of ductile 'ridges' at the fracture surface; all that were characteristic of hydrogen-induced cold cracking. In line with this, Vickers hardness measurements revealed maximum hardness as great as 381-382 HV and 371-378 HV in cases of the CGHAZ and weld metal microstructures, respectively. Furthermore, hardness traverses in the weld thickness direction revealed higher hardness values in the weld intermediate thickness than closer to the surface or the root, which was ascribed to inadequacy of the thermal effects of the ISR heat treatment. The occurrence of hydrogen cracking was attributed to simultaneous co-existence of several adverse factors: (i) excessively high weldment hardness, (ii) accidentally high initial hydrogen content of the applied SMAW electrode and (iii) inherently high structural rigidity and restraint of the component.",
author = "Pekka Nevasmaa and Sanni Yli-Olli and Olli Kortelainen and Arto Kiiski",
year = "2016",
language = "English",
series = "VTT Technology",
publisher = "VTT Technical Research Centre of Finland",
editor = "Pertti Auerkari",
booktitle = "Baltica X",
address = "Finland",

}

Nevasmaa, P, Yli-Olli, S, Kortelainen, O & Kiiski, A 2016, Failure analysis of a 2.25Cr-1Mo-0.25V steel heavy wall-thickness multi-pass welded component. in P Auerkari (ed.), Baltica X: International Conference on Life Management and Maintenance for Power Plants. VTT Technical Research Centre of Finland, Espoo, VTT Technology, vol. 261, BALTICA X - International Conference on Life Management and Maintenance for Power Plants, Helsinki-Stockholm, Finland, 7/06/16.

Failure analysis of a 2.25Cr-1Mo-0.25V steel heavy wall-thickness multi-pass welded component. / Nevasmaa, Pekka; Yli-Olli, Sanni; Kortelainen, Olli; Kiiski, Arto.

Baltica X: International Conference on Life Management and Maintenance for Power Plants. ed. / Pertti Auerkari. Espoo : VTT Technical Research Centre of Finland, 2016. (VTT Technology, Vol. 261).

Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientificpeer-review

TY - GEN

T1 - Failure analysis of a 2.25Cr-1Mo-0.25V steel heavy wall-thickness multi-pass welded component

AU - Nevasmaa, Pekka

AU - Yli-Olli, Sanni

AU - Kortelainen, Olli

AU - Kiiski, Arto

PY - 2016

Y1 - 2016

N2 - Crack-like defects were found in a low-alloy 2.25Cr-1Mo-0.25V steel multipass welded heavy wallthickness component prior to its usage. After welding, the component had been subjected to local Intermediate Stress Relief (ISR) heat treatment at 600-650°C, with the aim at removing diffusible hydrogen and enhancing partial tempering of the weldment microstructure before the final PWHT. The objective of the present paper was to investigate the actual fracture micromechanism of the discovered damage associated with the manufacturing stage of the component, in order to explain the inherent causes of failure. The metallographic and fractographic studies demonstrated (i) cracks propagating through the weld solidification structure as quasi-cleavage fractures, (ii) the presence of micro-cracks at thereby 'opened' solidification boundaries, as well as (iii) occasional appearance of ductile 'ridges' at the fracture surface; all that were characteristic of hydrogen-induced cold cracking. In line with this, Vickers hardness measurements revealed maximum hardness as great as 381-382 HV and 371-378 HV in cases of the CGHAZ and weld metal microstructures, respectively. Furthermore, hardness traverses in the weld thickness direction revealed higher hardness values in the weld intermediate thickness than closer to the surface or the root, which was ascribed to inadequacy of the thermal effects of the ISR heat treatment. The occurrence of hydrogen cracking was attributed to simultaneous co-existence of several adverse factors: (i) excessively high weldment hardness, (ii) accidentally high initial hydrogen content of the applied SMAW electrode and (iii) inherently high structural rigidity and restraint of the component.

AB - Crack-like defects were found in a low-alloy 2.25Cr-1Mo-0.25V steel multipass welded heavy wallthickness component prior to its usage. After welding, the component had been subjected to local Intermediate Stress Relief (ISR) heat treatment at 600-650°C, with the aim at removing diffusible hydrogen and enhancing partial tempering of the weldment microstructure before the final PWHT. The objective of the present paper was to investigate the actual fracture micromechanism of the discovered damage associated with the manufacturing stage of the component, in order to explain the inherent causes of failure. The metallographic and fractographic studies demonstrated (i) cracks propagating through the weld solidification structure as quasi-cleavage fractures, (ii) the presence of micro-cracks at thereby 'opened' solidification boundaries, as well as (iii) occasional appearance of ductile 'ridges' at the fracture surface; all that were characteristic of hydrogen-induced cold cracking. In line with this, Vickers hardness measurements revealed maximum hardness as great as 381-382 HV and 371-378 HV in cases of the CGHAZ and weld metal microstructures, respectively. Furthermore, hardness traverses in the weld thickness direction revealed higher hardness values in the weld intermediate thickness than closer to the surface or the root, which was ascribed to inadequacy of the thermal effects of the ISR heat treatment. The occurrence of hydrogen cracking was attributed to simultaneous co-existence of several adverse factors: (i) excessively high weldment hardness, (ii) accidentally high initial hydrogen content of the applied SMAW electrode and (iii) inherently high structural rigidity and restraint of the component.

M3 - Conference article in proceedings

T3 - VTT Technology

BT - Baltica X

A2 - Auerkari, Pertti

PB - VTT Technical Research Centre of Finland

CY - Espoo

ER -

Nevasmaa P, Yli-Olli S, Kortelainen O, Kiiski A. Failure analysis of a 2.25Cr-1Mo-0.25V steel heavy wall-thickness multi-pass welded component. In Auerkari P, editor, Baltica X: International Conference on Life Management and Maintenance for Power Plants. Espoo: VTT Technical Research Centre of Finland. 2016. (VTT Technology, Vol. 261).