Fig. 11 Hot corrosion attack of René 77 nickel-base alloy turbine blades. (a) Land-based, first-stage turbine blade. Notice deposit buildup, flaking, and splitting of leading edge. (b) Stationary vanes. (c) A land-based, first-stage gas turbine blade that had type 2 hot corrosion attack. (d More

Fig. 12 Heat-damaged turbine blades. (a) Heat-damaged first- or second-stage turbine blade (A), which remained intact but with a darkened appearance. It is common to have blades that appear to be in relatively good condition but with an underlying overtemperature condition. (b) Two third-stage More

Fig. 13 Flow diagram for remaining life assessment of gas turbine blades More

Fig. 14 Sectioning of turbine blades for metallographic examination. (a) Typical locations for cross sectioning of turbine blades. (b) View of Sectioned blade More

Fig. 3 The evolution of the processing of nickel-base superalloy turbine blades. (a) From left, equiaxed, directionally solidified, and single-crystal blades. (b) An exposed view of the internal cooling passages of an aircraft turbine blade. Source: Ref 5 More

Fig. 8 Two shipboard turbine blades. Pressure side shown facing out of the page. Arrows denote areas where heavy corrosion products are observed. More

Fig. 11 Microstructures of nickel-base Alloy 713C turbine blades. (a) Original structure prior to service. (b) Coarsening of γ' precipitates and elimination of secondary γ' caused by 5000 h of service More

Fig. 1 Macrostructure of three turbine blades: polycrystalline (left), columnar grain directionally solidified (center), and single-crystal directionally solidified (right) More

Fig. 28 (a) Photograph of fourth-stage turbine blades prior to removal. The first blade to fail is indicated with an arrow; an exhaust thermocouple is shown in the foreground. (b) Photograph of blade fracture surface after sectioning. Note the blue discoloration at the trailing edge. (c More

Fig. 12 (a) Photograph showing one of the intact steam turbine blades from the failed stage. The arrow indicates the fracture location. (b) Photograph of the fracture surface. Scale: millimeters. (c) Scanning electron fractograph of the initiation region showing a mixed transgranular More

Fig. 4 Failed second-stage turbine blade. (a) Photograph of failed blade, with fracture at the top of the image. (b) Stereomicroscopic image of fracture surface showing coarse, intergranular topology. (c) Scanning electron fractograph showing void coalescence on fracture surface. (d) Optical More

Fig. 105 Fracture surface of a cast aluminum alloy A357-T6 air-turbine blade. (a) Overall view of the fracture surface showing a large inclusion (dark) near the tip of the blade. Approximately 0.4×. (b) and (c) Decohesion at the interfaces between the inclusion and the aluminum matrix More

Fig. 9 Two portions of a modified type 403 stainless steel steam turbine blade damaged by liquid impingement erosion. The portion at left was protected by a shield of 1 mm (0.04 in.) thick rolled Stellite 6B brazed onto the leading edge of the blade; the portion at right was unprotected More

Fig. 10 Surface appearance at low magnification of a steam turbine blade eroded by water droplets. (a) 12% Cr steel blade material. (b) Stellite 6B shield More

Fig. 9 Corrosion products on the grain facets from SCC of a U-700 turbine blade, presumably from combustion-gas attack that induced SCC, with IG and transgranular modes shown More

Fig. 9 Gamma-prime overaging in a nickel-base alloy turbine blade material. (a) SEM micrograph of the blade material, showing the breakdown of the eutectic gamma prime (5) and the spreading of the coarse gamma prime. Smaller particles of fine aging gamma prime (4), which would appear between More

Fig. 20 Schematic of first-stage gas turbine blade that experienced cracking after 32,000 h in service. (a) Sectioning planes at three locations on the blade airfoil. (b) Cross-sectional view of the blade airfoil showing the cooling holes and numbering sequence More

Fig. 21 Oxidation and cracking at cooling holes in a turbine blade. (a) Trailing edge cooling hole surface showing oxidation and nitridation attack on the surface after 32,000 h of operation. (b) Crack found on the surface of No. 5 cooling hole. Oxidation on the crack surface and hole surface More

Fig. 2 Resulting fracture surface when gas turbine blade trailing edge crack is broken open in laboratory. More

Fig. 4 Metallographic cross section through gas turbine blade. Note differences in etched structure near surfaces. Etch: electrolytic, 20% sulfuric acid in methanol. 28× More