Effect of Post Weld Heat Treatment on the Microstructure and Electrochemical Characteristics of Dissimilar Material Welded by Butter Method

In the present study, the effect of post weld heat treatment (PWHT) on the microstructure and corrosion kinetics of butter welded Nickel Alloy 617 and 12Cr steel was investigated. Buttering was carried out on the 12Cr side with the Thyssen 617 filler metal. Furthermore, post weld heat treatment (PWHT) was conducted at 730 °C with a holding time of 4 h followed by furnace cooling. Optical Microscopy (OM) was conducted to study the microstructural evolution in dissimilar material welding as a result of PWHT. Moreover, Scanning Electron Microscopy with energy dispersive spectroscopy (SEM-EDS) was employed to determine the elemental concentrations in all important regions of the butter weld before and after the PWHT. In addition, the effect of PWHT on the corrosion kinetics of the butter weld was also investigated by potentiodynamic polarization measurements in 5 wt.% NaCl + 0.5 wt.% CH3COOH electrolyte at room temperature, 30 °C, 50 °C and 70 °C. The corrosion activation parameters were also determined for both the samples by using Arrhenius plots. The results revealed the higher susceptibility of corrosion of the butter weld after PWHT, which was attributed to the reduced Cr content in the heat affected zone of the 12Cr region due to the sensitization effect of the heat treatment, resulting in higher corrosion rates.

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Measurement of Residual Stresses in Thick Section Steel Electron Beam Welds

ASME 2010 Pressure Vessels and Piping Conference: Volume 6, Parts A and B ◽

10.1115/pvp2010-25314 ◽

2010 ◽

Cited By ~ 3

Author(s):

E. Kingston ◽

D. J. Smith ◽

G. Zheng ◽

C. Gill ◽

P. Hurrell

Keyword(s):

Heat Treatment ◽

Electron Beam ◽

Residual Stresses ◽

Post Weld Heat Treatment ◽

Hole Drilling ◽

Drilling Technique ◽

Fair Comparison ◽

Before And After ◽

Hoop Stresses ◽

Weld Heat

Residual stresses were measured and predicted in steel electron beam welded samples, one supplied by Rolls-Royce, UK, and a second by CEA, France. In the case of the Rolls-Royce sample, measurements were made before and after post-weld heat treatment. The deep hole drilling technique was applied to obtain measurements across and through the EB welds. It is shown that the tensile residual stresses are confined to a region either side of the EB weld that corresponds to about 20% of the wall thickness. Post-weld heat treatment is shown to substantially reduce the magnitudes of the peak residual stresses. Comparisons between measurements and predicted residual stresses in the Rolls-Royce sample show that predicted hoop stresses are substantially greater than measured although there is a fair comparison between measured and predicted radial stresses.

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Neutron and Synchrotron Diffraction Measurements of Residual Stress in Steel Weldments

Volume 5: High-Pressure Technology; Non-Destructive Evaluation; Student Paper Competition ◽

10.1115/pvp2007-26694 ◽

2007 ◽

Author(s):

Anna M. Paradowska ◽

John W. H. Price ◽

Raafat Ibrahim

Keyword(s):

Heat Treatment ◽

Residual Stress ◽

Stress Distribution ◽

State Of The Art ◽

Mechanical Tests ◽

Post Weld Heat Treatment ◽

Synchrotron Diffraction ◽

Before And After ◽

Strain Stress ◽

Weld Heat

This paper explores the use of state-of-the-art instruments such as neutron and synchrotron diffraction for evaluation of residual stress in carbon steel welded components. The study shows significant variation in transverse residual strain/stress distribution across the length of the weld. Measurements before and after post weld heat treatment are reported together with traditional mechanical tests. The changes in residual stress distribution as weld beads are added in multi-bead welds are also presented. Important practical results are: i) The start and end of the weld are the most critical parts of the weldment. Implementations of run-in and run-out (which are subsequently ground off) can minimize the residual stress at the start and end of the weld. ii) Manipulation of the sequence especially around the weld toes can minimize the value of the residual stress in that region. iii) Post weld heat treatment is very effective at reducing residual stresses.

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