| dc.description.abstract | Abstract. Friction stir welding (FSW) is a robust solid-state joining process increasingly applied to high-melting-point materials such as Cu, Fe, Ti, and their alloys, beyond conventional Al and Mg systems. However, tool life remains a critical limitation, particularly for H13 steel tools subjected to severe thermal and contact stresses that promote plastic deformation and wear. This study examines the influence of six heat treatment conditions on the tribological performance and durability of H13 tools during FSW of CuCrZr alloy by integrating controlled laboratory wear testing with bead-on-plate welding trials. The as-received H13 condition, characterized by a soft ferritic microstructure, exhibited low hardness and strength, resulting in severe plastic deformation and adhesion-plowing dominated wear, with material transfer to the tungsten carbide (WC) counterface. In contrast, quenching produced a fine lath martensitic microstructure, yielding ∼70.7% higher hardness, ∼65% higher yield strength, ∼70% higher ultimate tensile strength, and ∼81% lower wear-rate. Normalizing and tempering treatments caused progressive martensite coarsening, reducing hardness and increasing wear. Tribological analyses of wear scars, debris, and subsurface deformation identified adhesion, abrasion, surface fatigue, plowing, and mechanical mixing as dominant degradation mechanisms under cyclic loading. Welding trials over 120 mm showed that quenched, normalized, and short-duration tempered tools retained pin integrity, whereas others failed by deformation or shearing. Under extended welding (220 mm), only the quenched tool maintained structural integrity. These results establish direct correlations between heat treatment, microstructure, and tribological response, providing a mechanistic basis for optimizing H13 tool performance in FSW of CuCrZr alloys. | |
