Evaluation of Polycrystalline Diamond (PCD) Materials for FSW Tooling

Recently, techniques have been developed to fabricate friction stir welding tools using polycrystalline diamond (PCD) as the base material. Methods used to fabricate PCD tools are proprietary to the supplier and are unique due to its high hardness (4500 Vickers). However, it is this high hardness that makes PCD a strong candidate for long life FSW tools. To achieve appropriate metal flow during friction stir welding (FSW), FSW tools can require fine features on both the tool shoulder and tool pin. With conventional FSW tool materials, e.g., H13 tool steel or MP159, a multiphase alloy, etc., fine features can wear via abrasion resulting in limited FSW tool life and contamination of the weld zone. Conversely, PCD tools offer exceptional abrasion resistance. To date, no quantitative study has been performed to evaluate the potential of PCD for long life FSW tools. This study documents experimental results that evaluated PCD tool performance both for a large number (100) of initial plunges and for FSW in AA7075 up to 2,400 feet.