Application of shot peening in wind power gears

1. Why wind power gears need shot peening?

China has advantages in geographical and climatic conditions, where has vigorously developed wind power in recent years as a clean renewable energy source. Although it started late comapred with other countries, however, the installed wind power capacity of China ranks the third in the world now, behinding the United Kingdom and Germany. Furthermore, the common height of wind turbines reaches 120 meters, the volume and weight of components are large, leading to the fact that the costs of maintenance and repair are a great concern. Therefore, the operating life of the wind power gearbox needs to be guaranteed.

After the heat treatment of wind power gears, there left the oxidized layer on the surface. Before the finished product, the oxidazation layer needs to be completely cleaned to ensure the adhesion of the subsequent painting. To improve the fatigue life of wind power gears, the shot peening process has also been gradually introduced around the world. In addition to the removal of the oxidized layer, the surface is also further strengthened, and the residual compressive stress is introduced leading to an improved fatigue life.

2.Where are the failure positions of wind power gears?

Wind turbine gear failure positions:

a)Wheel body (rarely occurs)-fracture-structure

b)Tooth surface-pitting /scuffing-contact fatigue               

3、Commonly used wind power gear shot peening process

3.1Oxide layer removal via shot blasting  
a)Cleanup level：Sa2.5）

b)Recommended shot: S390 / HRC44-52

c)Shot blasting position: whole gear

3.2 Sandblasting of tooth surface-improve surface roughness

a)Cleanup level：Sa2.5

b)Recommended shot: Glass shot/ B40

d)Shot blasting position: Tooth root of gear

3.3Tooth surface strengthening (enable to be treated together with oxide layer cleaning)

a)shot intensity：0.38-0.46mmA

b)coverage（Test piece saturation method）：200%

c)surface roughness：≤Ra2.0 μm

d)Recommended shot: CW41 (1.0mm)/HV640 /G2

e)Shot peening position: Tooth root of gear

f)residual stress：There must be a point exceeding 1000 Mpa between 50-100 μm (normal direction of tooth root 30 ° tangent)

4. Shot blasting machines for wind power gears

4.1 Strengthening of tooth surface of wind power gear (considering cleaning function)

Recommended equipment: OH1717-P380 / 3/15

                                             Hanging shot blasting machine

   
4.2 Sandblasting of gear tooth surface of wind power

Recommended equipment: MT25-G80II / 1 / R

                                             Large rotary table sandblasting machine