TWI Industrial Member Report Summary 951/2010
By J G Perrett
TWI Member Report 915 (Perrett, 2008), describes work carried out on the evaluation of tool materials for the friction stir welding (FSW) of 6mm AISI 304L austenitic stainless steel. The aim was to test and compare the leading candidate FSW tool materials and provide a measure of the performance of these materials. The report concluded that there were two very different leading candidate materials, polycrystalline boron nitride (PCBN) and a tungsten-rhenium alloy. Since Perrett (2008) was published, there have been major tool material developments, due to the ongoing research drive into high-softening temperature (>800°C) FSW around the world. These materials include composite refractory metal/ceramic materials containing tungsten-rhenium (W-25%Re) and cubic boron nitride (cBN) developed by MegaStir Technologies, and tungsten-rhenium with hafnium carbide (HfC) additions developed by Rhenium Alloys Inc in the USA.
This report continues the work in Perrett (2008), by studying the worn surfaces of the two FSW tool materials found to be the most effective. The report then briefly describes the effect tool wear when welding with coated low cost ceramic materials. Also a preliminary study into the effect of preheating the workpiece using an induction preheating system is described. The latest tool materials and designs are discussed, and a full FSW performance assessment of these tool materials is provided, using 6mm thickness AISI 304L austenitic stainless steel plate as the weld test material.
- Assess the worn surfaces of the PCBN and W-25%Re FSW tools used in Perrett (2008).
- Investigate the influence of coating low cost ceramic FSW tools with respect to increasing tool longevity.
- Preliminary study to determine whether preheating the workpiece increases tool lifetime when compared with the baseline data for a W-25%Re tool.
- Test, compare and evaluate the performance of the latest composite and refractory metal tool materials for the FSW of 6mm thickness AISI 304L austenitic stainless steel plate.