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<p>This paper systematically examines the effects of post-weld heat treatment (PWHT) at 600&#xa0;°C for 1 and 10 hours on the microstructural evolution, hardness, and corrosion behavior of shielded metal arc welded (SMAW) 308L/309L/high strength low alloy steel (HSLA) dissimilar metal cladding. Advanced electron backscatter diffraction (EBSD) was the core characterization tool to quantify phase distribution, grain boundary character distribution (GBCD), and local misorientations, complemented by vicker’s hardness testing and potentiodynamic polarization (PDP). In the as-clad state, HSLA consisted of fine equiaxed ferrite (99.7%) with a high fraction of special coincidence site lattice (CSL) boundaries (14.2%); 309L solidified as columnar austenite with δ-ferrite (8.8%) and a strong texture; and 308L exhibited a duplex <b>γ</b>– δ structure with higher skeletal ferrite (26.8%). After PWHT-1&#xa0;hr: HSLA recovery (Low angle grain boundaries (LAGBs) increased); 309L near-complete δ → γ (ferrite ~ 0.5%) with austenite coarsening from the loss of Zener pinning; 308L ferrite network limiting grain growth. After 10&#xa0;hr PWHT: HSLA partial recrystallization with partial CSL restoration; 309L grain boundary secondary precipitation (sigma-like; ~ 4.2%) reimposing pinning and refining grains; 308L continued δ-ferrite decomposition with a modest CSL increase. Hardness trends reflected recovery, tempering of the heat affected zone (HAZ), and the competing effects of ferrite dissolution and precipitation pinning, without requiring large grain growth in 308L. Corrosion performance peaked after the PWHT-1&#xa0;hr due to phase homogenization and stress relief but degraded markedly after 10&#xa0;hr as sensitization promoted intergranular attack in the stainless layers. The results identify a narrow PWHT window—short exposures at 600&#xa0;°C that dissolve δ-ferrite without triggering sensitization or extensive sigma precipitation—as the most effective strategy to balance microstructural stability, mechanical softening, and corrosion resistance in HSLA/309L/308L claddings.</p>

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Effect of Post-Weld Heat Treatment on Microstructural Evolution and Corrosion Performance of SMAW-Deposited 308L/309L Weld Overlays on HSLA Steel

  • 期刊论文

  • 发表日期：

    2026年3月5日

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  • V. Shashikanth,
  • Raffi Mohammed,
  • Arun Kumar Gurrala

摘要

This paper systematically examines the effects of post-weld heat treatment (PWHT) at 600 °C for 1 and 10 hours on the microstructural evolution, hardness, and corrosion behavior of shielded metal arc welded (SMAW) 308L/309L/high strength low alloy steel (HSLA) dissimilar metal cladding. Advanced electron backscatter diffraction (EBSD) was the core characterization tool to quantify phase distribution, grain boundary character distribution (GBCD), and local misorientations, complemented by vicker’s hardness testing and potentiodynamic polarization (PDP). In the as-clad state, HSLA consisted of fine equiaxed ferrite (99.7%) with a high fraction of special coincidence site lattice (CSL) boundaries (14.2%); 309L solidified as columnar austenite with δ-ferrite (8.8%) and a strong texture; and 308L exhibited a duplex γ– δ structure with higher skeletal ferrite (26.8%). After PWHT-1 hr: HSLA recovery (Low angle grain boundaries (LAGBs) increased); 309L near-complete δ → γ (ferrite ~ 0.5%) with austenite coarsening from the loss of Zener pinning; 308L ferrite network limiting grain growth. After 10 hr PWHT: HSLA partial recrystallization with partial CSL restoration; 309L grain boundary secondary precipitation (sigma-like; ~ 4.2%) reimposing pinning and refining grains; 308L continued δ-ferrite decomposition with a modest CSL increase. Hardness trends reflected recovery, tempering of the heat affected zone (HAZ), and the competing effects of ferrite dissolution and precipitation pinning, without requiring large grain growth in 308L. Corrosion performance peaked after the PWHT-1 hr due to phase homogenization and stress relief but degraded markedly after 10 hr as sensitization promoted intergranular attack in the stainless layers. The results identify a narrow PWHT window—short exposures at 600 °C that dissolve δ-ferrite without triggering sensitization or extensive sigma precipitation—as the most effective strategy to balance microstructural stability, mechanical softening, and corrosion resistance in HSLA/309L/308L claddings.