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INFLUENCE OF NITRIDING ON MICROSTRUCTURE AND FATIGUE BEHAVIOUR OF A SOLUTE‐RICH BETA TITANIUM ALLOY
Author(s) -
Müller C.,
Holzwarth U.,
Gregory J. K.
Publication year - 1997
Publication title -
fatigue and fracture of engineering materials and structures
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.887
H-Index - 84
eISSN - 1460-2695
pISSN - 8756-758X
DOI - 10.1111/j.1460-2695.1997.tb01519.x
Subject(s) - nitriding , materials science , microstructure , metallurgy , alloy , tin , ultimate tensile strength , titanium alloy , titanium , ductility (earth science) , toughness , composite material , layer (electronics) , creep
— The solute‐rich beta titanium alloy Ti‐3Al‐8V‐6Cr‐4Mo‐4Zr was subjected to 1500 bar nitrogen pressure at elevated temperatures (500–920°C), leading to a diffusion layer with a high surface hardness. Microstructural, crystallographic and compositional analyses indicate that TiN (δ) and Ti 2 N (ε) are formed at temperatures exceeding 815°C. The increased concentration of nitrogen, which is a potent α‐stabilizer in titanium, also causes α‐Ti to form near the surface. The nitriding treatment does not significantly alter the tensile properties or fatigue limit in solution heat treated material. A subsequent ageing treatment of 72 h at 440°C and 16 h at 500°C reduces toughness significantly, allowing cracks induced by nitriding to propagate more easily into the bulk. Tensile ductility and fatigue performance of aged nitrided Ti‐3Al‐8V‐6Cr—4Mo‐4Zr are thus significantly lower than in the untreated reference condition.