Friction Hydro Pillar Processing
Friction hydro-pillar processing (FHPP) is a solid-state joining technology which can be used for filling of surface and sub-surface cracks in thick metals. For example, FHPP was attempted for the first time to repair cracks in space shuttle external components of high-strength aluminum alloys. FHPP is also considered in repairing surface cracks in steam turbine rotors of a high-strength, high-temperature-resistant steel (grade 26NiCrMoV14-5) (Ref). Alternative methods such as fusion welding processes for in-service repairing of cracks in components of these high-strength steels remained difficult because of their high hardenability and mandatory need of pre-heating and post-weld heat treatment. In contrast, initial FHPP trials could achieve joint strengths up to 90% of the base materials in high-strength steel components, especially those used for petrochemical and thermal power plants. In particular, pressurized pipes and vessels of AISI 4140 steel are widely used in the power ge ...
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