Study of Heat Input Effects on the Microstructure of Lean Duplex 2101 Shielded Metal Arc Weld and Its Effect on Mechanical Properties, Corrosion, and Scratch Behavior

In the present study, shielded metal arc welding (SMAW) with electrode ER2209 was carried out on lean duplex grade LDX2101 by varying heat inputs, low heat (LH) 0.85 kJ/mm, and high heat (HH) 1.3 kJ/mm. The paper’s main objective was to understand the influence of heat inputs on microstructural behavior and its effect on the mechanical properties of weldments. Microstructure and volumetric phase analysis of weldments were done using an optical and scanning electron microscope. Grain boundary austenite, intra-granular austenite and Widmanstatten austenite, along with ferrite were observed in the microstructure of the weld zones. The morphology of the weldment revealed that the ferrite–austenite phase ratio can be adjusted by altering the heat inputs. Important mechanical properties such as tensile strength, impact toughness, micro-hardness and scratch hardness were investigated to understand the weld performance. The SMAW weldments exhibited an increase in micro-hardness, with values changing (from 227 ± 2.8 to 246 ± 5.2 HV₁₀) for LH SMAW and (from 232 ± 3.2 to 242 ± 2.7 HV₁₀) for HH SMAW. The tensile strength of the LH SMAW was slightly higher However, this enhancement in mechanical properties came at the expense of a slight reduction in ductility, as indicated by a fall in the percentage of elongation from 28.07 to 22.86. Impact toughness of the LH SMAW was 88.7% higher than the HH weldments. Electrochemical measurements of weldments were carried out using the potentiodynamic polarization test to estimate the corrosion rate. Scratch hardness was evaluated to understand the tribological characteristics of the weldment surface. The overall performance of the LH input weld exhibited promising results compared to the high heat.