The Effect of Post Weld Heat Treatment on Mechanical Properties of Friction-Welded Alloy 718 and SNCRW Stainless Steel

Abstract

The effect of post weld heat treatment on mechanical properties of friction welded Alloy 718 and SNCRW was investigated. Friction welding tests were carried out at a constant rotation speed and pressure. Optimum friction condition was found to be the friction pressure of 25kg/cm2, friction time of 40sec, upset pressure of 80 kg/cm2, and dwell time of 5sec. After friction welding tests, post weld heat treatments were performed in the temperature range of 500-900°C for 8hrs in order to investigate the microstructure and mechanical properties of weld joint. Specimens with the post weld heat treatment at 720°C for 8hrs show optimal mechanical properties. Residual stress of post weld heat treated specimens was measured to weld joint in the same temperature range. After friction welding tests on samples with a diameter of 80mm, tensile properties of post-weld-heat-treated and non-heat-treated samples were compared.

Microstructure and mechanical properties of friction welded alloy 718

“…Bu et al [16] reported that with increasing friction time, the temperature gradient in the axial direction decreases mainly due to very high energy given in the initial stage and low heat conduction of alloy 718. Kim et al [17] have observed that an aging treatment after friction welding improves hardness and tensile properties of friction welded alloy 718 and SNCrW stainless steel (chemical composition (in wt. %) of SNCrW stainless steel is 0.2 C, 1.4 Si, 19.8 Cr,9.5 Ni and 68.3 Fe).…”

Rotary friction welding of Inconel 718 – AISI 304 stainless steel dissimilar joint

“…The formation of less flash on the Inconel 718 side may be attributed to the high strength of Inconel 718 at higher temperatures than SS304 during friction welding. On the contrary, SS304 experiences a sharp decrease in flow stress at higher temperatures which softens the alloy enabling it to undergo plastic deformation [29].…”

“…A reduction in impact toughness was observed upon subjecting the joint to a post-weld heat treatment. In a similar study, residual stresses were reduced [29] after subjecting an Inconel 718 – SNCrW friction weld to a post-weld heat treatment. Hence, a post-weld heat treatment could significantly influence the microstructure and the mechanical properties of a dissimilar joint.…”

Influence of Microstructure and Mechanical Properties of Dissimilar Rotary Friction Welded Inconel to Stainless Steel Joints

“…This is due to the generation of precipitates during PWHT. Kim et al [27] explored the effect of PWHT on the mechanical properties of friction-welded Alloy 718 and SNCrW (in wt% 20 Cr, 10 Ni, 2 W, 1.4 Si, and 66.6 Fe) stainless steel. They found that PWHT samples resulted in good mechanical properties due to the formation of the γ" phase.…”