Steel

This project looks to determine the most effective tempering heat-treatment parameters to optimize the mechanical properties of the golf club and mitigate potential defects surrounding the AISI 4140/8620 weld-interface. The published work on this weld is minimal, although TaylorMade’s prior investigation of prematurely-failed clubs proved there to be cracking in the weld’s heat-affected zone (HAZ). The study analyzes a range of tempering parameters to ascertain the effect on the microstructural and mechanical properties of the welded joint. There were four test groups assigned specific parameters; Group 1, Group 2, Control, and Group 3. To determine each group’s mechanical properties, tensile testing was performed on bar-stock and welded material. The failure-modes of all samples were categorized according to ductile and brittle behavior. Microstructures for the tested samples were characterized using metallography to discover regions of interest for microhardness testing so the localized mechanical properties could be recorded. The tensile testing concluded that the control group displayed the highest degree of toughness, maintaining high strength and appropriate elongation in both the bar stock and welded materials; the microhardness testing and metallography supported this conclusion from tensile testing. Group 2 and Group 3 performed well in the tensile testing and showed appropriate microstructures, but fell short in comparison to the control group indicating that the control test group consisted of the most appropriate parameters.