Microstructural stability of titanium-modified type 316 and type 321 stainless steel

Journal Article · Sat Nov 01 00:00:00 EST 1975 · Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science

DOI:https://doi.org/10.1007/BF03161827· OSTI ID:4072850

Grot, Arnold S.; Spruiell, Joseph E.

Optical metallography, transmission electron microscopy, and X-ray diffraction from bulk extracted residues were used to investigate the microstructural stability in the temperature range 450°C to 950°C of a titanium-modified type 316 stainless steel and to compare this steel to a type 321 heat. The effect of cold deformation prior to aging was also investigated. Compared to standard type 316 stainless steel, the nucleation of M₂₃C₆ was delayed and its growth retarded in the titanium modified alloy due to early formation of TiC and Ti₄C₂S₂ which reduced the carbon content in the matrix. Precipitation of the intermetallic σ and χ phases was faster in the titanium modified alloy. The type 321 material formed both M₂₃C₆ and the intermetallic phases less rapidly than either standard or titanium-modified type 316 steels. The relative tendencies toward intermetallic compound formation in various austentic stainless steels are discussed in terms of an “effective equivalent Cr content” remaining in the austenitic matrix after carbide precipitation. Cold work accelerated the precipitation rate of M₂₃C₆ and σ, but it suppressed χ formation due to preferential early σ formation. Early sigma formation was often associated with recrystallization of the cold worked matrix. Finally, mechanisms accounting for this behavior are discussed.

• Research Organization: Pratt and Whitney Aircraft, East Hartford, CT
• Sponsoring Organization: USDOE
• NSA Number: NSA-33-015289
• OSTI ID: 4072850
• Journal Information: Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science, Vol. 6, Issue 11; Other Information: Orig. Receipt Date: 30-JUN-76; ISSN 1073-5623
• Publisher: ASM International
• Country of Publication: United States
• Language: English

Related Subjects

N50230* -Metals
Ceramics
& Other Materials-Metals & Alloys-Properties
Structure & Phase Studies
360102* -Materials-Metals & Alloys-Structure & Phase Studies
*STAINLESS STEEL-316- MICROSTRUCTURE
*STAINLESS STEEL-321- MICROSTRUCTURE
AGING
COLD WORKING
DEFORMATION
ELECTRON MICROSCOPY
HIGH TEMPERATURE
RECRYSTALLIZATION
TITANIUM ADDITIONS
TITANIUM CARBIDES
VERY HIGH TEMPERATURE
X-RAY DIFFRACTION