The fracture behavior of tungsten wire reinforced superalloy composites during isothermal forging
- PDF / 3,863,753 Bytes
- 10 Pages / 594 x 774 pts Page_size
- 101 Downloads / 196 Views
I.
INTRODUCTION
INTEREST has emerged in recent years in the development of wire reinforced superalloy composite materials. 1,2In particular, a study was described in 1976 of the processing of composite samples of Mar-M200 nickel-base superalloy reinforced with high strength tungsten wires] These materials were being considered for use in industrial gas turbine engines for hot section blades and vanes. Major efforts were being made to develop net-shape processing technology, using hot isostatic pressing as the primary fabrication process. However, it was suggested that isothermal forging might be necessary to complete the shaping and sizing operations. Accordingly, work was started to examine the isothermal forging of these materials under well-controlled laboratory conditions .4 Some results on the flow and fracture behavior of these composites are described in Reference 5. The purpose of this paper is to examine the fracture of these materials in more detail, and to discuss these results in terms of the practical forging of turbine airfoil shapes.
II.
MATERIALS
The composite material was prepared from -140 mesh argon atomized Mar-M200 powder and high strength thoriated tungsten wire of 0.5 mm diameter. The tungsten wires had a 3 to 4/zm thick coating of hafnium nitride to prevent nickel-induced recrystallization. The volume percentage of wires in the composite was about 40 pct. Samples were consolidated by hot isostatic pressing (hipping) following procedures described in Reference 3. Originally, hipping conditions of 1050 ~ MPa/2 hours were used, but consolidation was not complete. Voids existed in the matrix and cracks were observed in the wires as shown in Figure 1. A. Y. KANDEIL, formerly with Mechanical and Aeronautical Engineering Department, Carleton University, Ottawa, Ontario, Canada, K1S 5B6, is now with Faculty of Engineering, University of Qatar, P.O. Box 2713, Doha, Qatar. J-P. A. IMMARIGEON and W. WALLACE are with National Aeronautical Establishment, National Research Council of Canada, Ottawa, Ontario, Canada, K1A 0R6. M.C. de MALHERBE is with the Mechanical and Aeronautical Engineering Department, Carleton University, Ottawa, Ontario, Canada, K1S 5B6. Manuscript submitted August 20, 1981. METALLURGICALTRANSACTIONS A
Therefore, the temperature was raised to 1150 ~ resulting in much improved consolidation (Figure 2(a)). However, some defects of the type described above could usually be
Fig. 1 --Mar-M200/40 pct W fiber composite pressed at 1050 ~ ing transfiber cracking and interfiber voids.
(a)
show-
(b)
Fig. 2--Cross-sections of composite materials pressed at 1150 ~ showing (a) uniform distribution of fibers, and (b) nonuniform distribution of fibers and matrix voids. VOLUME 15A, MARCH 1984--501
(a)
(b)
Fig. 3--Electron microprobe results from as-pressed composite specimens; (a)X-ray line scan and (b)X-ray image showing large concentrations of hafnium in the surface diffusion barrier and transfiber crack.
400
found in regions containing nonuniform distributions of wire as shown in F
Data Loading...
