Investigation of the y´ Precipitates Dissolution in a Ni-Based Superalloy During Stress-Free Short-Term Annealing at High Homologous Temperatures

• The equiaxed Ni-based superalloy Rene 108 was subjected to short-term annealing at five temperatures between 900 degrees C and 1100 degrees C. The phase composition, phase lattice parameters, microstructure, stereological parameters, and chemical composition of y´ precipitates were investigated by thermodynamic simulations, X-ray diffraction, scanning and transmission electron microscopy, and energy-dispersive X-ray spectroscopy. Analysis of the y and y´ lattice parameters using the Nelson-Riley extrapolation function showed that the misfit parameter for temperatures 900 degrees C to 1050 degrees C is positive (decreasing from 0.32 to 0.11 pct). At 1100 degrees C, the parameter becomes negative, delta = - 0.18 pct. During the short-term annealing, gamma ‘ precipitates dissolution occurred progressing more rapidly with increasing temperatures. The surface fraction of y´ precipitates decreased with increasing temperature from 0.52 to 0.34. The dissolution of gamma ‘ precipitates did not only proceed through uninterrupted thinning of each individual precipitate, but also included more complex mechanisms, including splitting. Based on transmission electron microscopy, it was shown that after y´ precipitates dissolution, the matrix close to the y/y interface is strongly enriched in Co and Cr and depleted in Al.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Materialteknik -- Bearbetnings-, yt- och fogningsteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering -- Manufacturing, Surface and Joining Technology (hsv//eng)

TEKNIK OCH TEKNOLOGIER  -- Materialteknik -- Metallurgi och metalliska material (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering -- Metallurgy and Metallic Materials (hsv//eng)

NATURVETENSKAP  -- Kemi -- Materialkemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Materials Chemistry (hsv//eng)

Nyckelord

gamma

preciptitate

dissolution

ni-based superalloy

homologogues

temperatures. Rene 108

Production Technology

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