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Khodamoradi, Zahra

University of British Columbia

In industrial applications, particularly those involving high temperatures and corrosive environments, weld overlays play a crucial role in enhancing component durability. This thesis investigates the influence of Gas Metal Arc Welding (GMAW) process parameters on residual stress and distortion in Inconel 686 weld overlays, a material chosen for its excellent corrosion resistance and crack mitigation properties. While Inconel 686 shows promise, the formation of residual stresses and distortion during welding processes remains a challenge, potentially leading to material failure or increased post-weld processing requirements. Through systematic experimentation and analysis of six welded plates using Electronic Speckle Pattern Interferometry (ESPI) and Coordinate Measuring Machine (CMM), this research examines the effects of key GMAW parameters: arc voltage, travel speed, wire feed speed, bead overlap, and heat input. The findings reveal complex relationships between welding parameters and resultant stress states. Increasing heat input from 426.37 J/mm to 533.07 J/mm led to a 22% increase in transverse residual stress, reaching tensile stresses of 184 MPa due to non-uniform thermal contraction. Notably, two of the samples (RS6 and RS14) showed extreme cases with transverse residual stress peaks of 614.9 MPa and 693.4 MPa, respectively, exceeding the material's yield strength (421-399 MPa). Higher arc voltage (25V compared to 19V) resulted in more uniform but elevated stress distributions, while increased wire feed speed (from 99.9 mm/sec to 166.3 mm/sec) amplified thermal gradients, leading to a 56% increase in parallel distortion. This increase is attributed to greater heat introduction in the weld zone, accelerating base and filler material melting and depositing more materials. Decreasing the bead overlap ratio from 1/2 to 1/3 led to an 11% elevation in transverse residual stress, accompanied by substantial increases in distortion magnitude: 63% transversely and 45% longitudinally. Distortion measurements consistently showed greater deformation perpendicular to the weld line, particularly under high heat input conditions. These results underscore the critical balance between heat input and other process parameters to minimize residual stress and distortion, leading to more durable and reliable weld overlays. These findings offer practical insights for industries seeking to enhance equipment performance while minimizing post-weld treatments and operational downtime.

Text

2025-01-27

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/90210

Mechanical Engineering

University of British Columbia

UBCO

http://creativecommons.org/licenses/by-nc-nd/4.0/