Initiation and growth of small fatigue cracks in a nickel-base superalloy Mei, Z., Krenn, C.R. and Morris, J.W. Jr. Metall. Mater. Trans. A (1995) 26A (8), 2063–2073

High temperature low cycle fatigue properties and fracture behavior of Inconel 625 nickel-base superalloy welding joint at 760oC were investigated under fully reversed total strain-controlled mode. The fatigue life and cyclic stress-strain data were analyzed to determine the individual strain fatigue parameters. It is noted that the welding joint exhibits the cyclic strain hardening and stability. The fatigue cracks initiate predominantly on the free surface of fatigue specimens and propagate in an intergranular mode or a mixed transgranular and intergranular mode.

Download Full-text

Braze Repair of MA754 Aero Gas Turbine Engine Nozzles

Volume 5: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls, Diagnostics and Instrumentation; Education; General ◽

10.1115/89-gt-235 ◽

1989 ◽

Cited By ~ 3

Author(s):

J. E. Elder ◽

R. Thamburaj ◽

P. C. Patnaik

Keyword(s):

Fatigue Cracks ◽

Oxide Dispersion Strengthened ◽

Experimental Program ◽

Nickel Base Superalloy ◽

Turbine Engine ◽

Repair Procedure ◽

Brazed Joints ◽

Nickel Base ◽

Thermal Fatigue Cracks ◽

Base Superalloy

MA754, an oxide-dispersion strengthened nickel-base superalloy, is the vane material being used in the High Pressure Turbine (HPT) Nozzle of the F404-400 turbofan engine. Thermal fatigue cracks are known to develop in the nozzle vanes during service and the component replacement costs can, in general, be very high. Attempts to demonstrate the feasiblity for braze repair of MA754 have thus far yielded little success. An experimental program aimed at developing a braze repair procedure for healing cracks in MA754 HPT nozzles is described. Thirteen different braze compositions, using two different brazing times and gap widths, are evaluated. Experimental results are described detailing the microstructure, degree of oxide agglomeration and porosity in the region of the brazed joints. The feasibility of applying a braze repair procedure to the nozzle component is discussed.

Download Full-text

Improvement of Thermal Fatigue Resistance of A Wrought Nickel-Base Superalloy by Laserglaze

MRS Proceedings ◽

10.1557/proc-58-415 ◽

1985 ◽

Vol 58 ◽

Author(s):

Zhao Qi ◽

Ge Yunlong ◽

Hu Zhuangqi ◽

Jiang Ming ◽

Shih Changshu

Keyword(s):

Heat Treatment ◽

Fatigue Resistance ◽

Thermal Fatigue ◽

Fatigue Cracks ◽

Nickel Base Superalloy ◽

Post Heat Treatment ◽

Thermal Fatigue Resistance ◽

Nickel Base ◽

Thermal Fatigue Cracks ◽

Base Superalloy

ABSTRACTLaserglaze with appropriate post heat treatment has improved the thermal fatigue resistance of a wrought nickel-base superalloy. It was found that laserglaze was able to eliminate the blocky MC phase, refine grains and form a very interesting microstructure of serrated grain boundaries. Careful selection of post heat treatment markedly increased the strength in the laser irradiated region. The initiation and propagation of thermal fatigue cracks were suppressed by this novel microstructure.

Download Full-text

Dependence of Intergranular Fracture on Boundary Topography and Cohesion

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100071193 ◽

1973 ◽

Vol 31 ◽

pp. 150-151

Author(s):

J. E. Doherty ◽

A. F. Giamei ◽

B. H. Kear ◽

C. W. Steinke

Keyword(s):

Grain Boundary ◽

Room Temperature ◽

Nickel Base Superalloy ◽

Boundary Shear ◽

Room Temperature Ductility ◽

Solid Solution Matrix ◽

Nickel Base ◽

Solution Matrix ◽

Different Levels ◽

Base Superalloy

Recently we have been investigating a class of nickel-base superalloys which possess substantial room temperature ductility. This improvement in ductility is directly related to improvements in grain boundary strength due to increased boundary cohesion through control of detrimental impurities and improved boundary shear strength by controlled grain boundary micros true tures.For these investigations an experimental nickel-base superalloy was doped with different levels of sulphur impurity. The micros tructure after a heat treatment of 1360°C for 2 hr, 1200°C for 16 hr consists of coherent precipitates of γ’ Ni3(Al,X) in a nickel solid solution matrix.

Download Full-text

Characterization of Coherent, Ordered Precipitates in Nickel-Base Alloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100071168 ◽

1973 ◽

Vol 31 ◽

pp. 144-145

Author(s):

B. H. Kear ◽

J. M. Oblak

Keyword(s):

Stable Phase ◽

Nickel Base Superalloy ◽

Alloy 718 ◽

Commercial Alloy ◽

Precipitate Morphology ◽

Continuous Precipitation ◽

Nickel Base ◽

Base Superalloy ◽

Strengthening Precipitate

A nickel-base superalloy is essentially a Ni/Cr solid solution hardened by additions of Al (Ti, Nb, etc.) to precipitate a coherent, ordered phase. In most commercial alloy systems, e.g. B-1900, IN-100 and Mar-M200, the stable precipitate is Ni3 (Al,Ti) γ′, with an LI2structure. In A lloy 901 the normal precipitate is metastable Nis Ti3 γ′ ; the stable phase is a hexagonal Do2 4 structure. In Alloy 718 the strengthening precipitate is metastable γ″, which has a body-centered tetragonal D022 structure.Precipitate MorphologyIn most systems the ordered γ′ phase forms by a continuous precipitation re-action, which gives rise to a uniform intragranular dispersion of precipitate particles. For zero γ/γ′ misfit, the γ′ precipitates assume a spheroidal.

Download Full-text