Application of shot peening in turbine blades

1.Why turbine blades need shot peening?

Blade is one of the important components of the engine. However, because the blade of the engine is a heteromorphic curved surface, thin in thickness, opearting in high temperature environment, and subjects to alternating fatigue stress, it is necessary to carry out shot peening before coating after manufacturing to improve its fatigue strength, service life and fatigue resistance.

Shot peening process is to use compressed air to spray a large number of shots on the surface of the workpiece, accumulates a large amount of compressive stress on the surface of the workpiece, so that the resistance of crack initiation and propagation under alternating fatigue stress of the blade is improved, thus improving the ability of anti-corrosion and fatigue damage. In addition, in the process of shot peening, dynamic recrystallization will take place in the surface structure under the strong impact of the projectile, the surface structure will be refined and the compressive residual stress magnitude will be increased, which can greatly improve the fatigue strength of the workpiece.

2. Where are the failure positions of turbine blades?  The failure positions of turbine blades：

a） Blade body - alternating stress

B） Tenon - fretting fatigue               

3. Shot peening process commonly used in turbine blades

3.1Blade surface cleaning and sand blasting

a) Coverage (visual or 30 times magnifying glass method): 98%

b) Roughness: ≥ Ra4

c) Recommended shot: green silicon carbide / 16 mesh

d) Treated position:whole blade

3.2 Shot peening of blade surface (different sizes and different materials use different processes)

a) Shot peening intensity: 0.2-0.3mmA

b) Coverage (30 times magnifier method): 98%

c) Roughness: Ra3.2

d) Recommended shot: CW17 (0.4mm) / HV640 / G3

e) Executive standard of shot material: SAE AMS 2431

f) Shot peening position: blade body and leading and trailing edge R

g) Protected position: tenon

3.3 Shot peening of tenon surface (different sizes and materials use different processes)

a) Shot peening intensity: 0.13-0.18mmA

b) Coverage (30 times magnifier method): 98%

c) Roughness: Ra1.6

d) Recommended shot: S110 / HRC55-62

e) Executive standard of shot material: SAE AMS 2431

f) Peening position: tenon working face

g) Protected position: blade body

4. Shot peening machines for turbine blades

4.1Blade surface cleaning and sand blasting

Recommended equipment: 5MT200-G15 / 1 / R

5-position trolley robot shot peening machine

4.2Shot peening on blade surface

Recommended equipment: MT800-G15 / 1 / R

Trolley robot shot peening machine

4.3Shot peening of tenon surface

Recommended equipment: 4MT1200-G15 / 1 / R

4-position large rotating table robot shot peening machine