Friction surfacing and cold spray deposition for surface crack repair in austenitic stainless steels

Abstract

Two technologies, friction surfacing (FS) and cold spray deposition (CSD), have been investigated for field repair of cracks in 304 L austenitic stainless steel. Both technologies are low-heat-input, solid-state technologies that do not introduce the detrimental effects of solidification, such as compositionally segregated microstructures and shrinkage stresses. Friction surfacing was performed using a 304L stainless steel rod over the substrate of the same material. The process was performed at a high spindle speed of 20,000 RPM allowing for process forces below 500 N to be used effectively. Spherical gas-atomized 304L stainless steel powder, in size range of 25-44 mu m, was used as feedstock powder for the cold spray process for deposition on 304L substrates. Both technologies showed leak-tight crack repair capabilities on similar to 30-50 mu m wide simulated through-crack specimens based on helium leak tests.