João Gandra

Friction stir processing

Abstract: Friction stir processing (FSP) is a recently developed metalworking technology based on the same basic principles as friction stir welding (FSW). Using a non-consumable rigid tool, FSP can be applied for the superficial or bulk processing of metallic materials. Although pioneer investigations studied its application to processing aluminium and magnesium alloys, recent research addresses its application to ferrous, copper and bronze alloys. Most common applications target localized microstructural modification in thin surface layers for specific property enhancement. It has proven to be an effective treatment to achieve major microstructural refinement, densification and homogeneity of the processed zone, as well as elimination of defects from other manufacturing processes. Processed surfaces also have shown an improvement of mechanical properties, such as hardness, tensile strength, fatigue, corrosion and wear resistance. A uniform equiaxial fine grain structure has proven to be essential to enhance material superplastic behaviour. The present chapter presents an overview of process principles and main research topics.

Process Developments in Friction Surfacing for Coatings Applications

The present work focused on the production of coatings of AISI1024, AISI1045 and AISIH13 over mild steel and AA6082-T6 over AA2024-T3 by friction surfacing. Performance criteria were established to quantify material deposition rate and specific energy consumption aiming to compare friction surfacing with most direct concurrent technologies such as laser and arc welding based cladding. Simple analytical models were developed to estimate the rod consumption and the power and energy consumption rates. Friction surfacing is a competitive technology considering energy efficiency and power consumption in comparison with mainstream processes. However, coating processes based on wire or powder feed are more competitive, since they allow continuous feeding of deposited material. The effect of process parameters was also assessed and it was seen they have different impacts on process efficiency and deposition rate for each material combination.