Application fields:
Induced and forced draft fans in boilers and kilns, cement and lime dust handling, biomass and waste-to-energy plants, steel plant dust extraction, and chemical process blowers.
Technical principles and processes:
Blades and the inlet cone are grit blasted and, where erosion has thinned the profile, rebuilt before coating. A tungsten carbide or alumina-titania ceramic layer is applied by HVOF or atmospheric plasma spray depending on the gas temperature and dust chemistry. The impeller is then balanced to the original grade.
Coating performance:
- Erosion resistance improved 3-6 times over mild steel blades
- Coating thickness 0.15-0.40 mm on blade faces and leading edges
- Withstands continuous service up to roughly 540 degrees C with ceramic
- Impeller balanced after coating to control vibration
- Extended intervals between blade replacement and rebalancing
风机叶轮耐磨涂层加工：针对含尘、腐蚀性烟气工况，对叶片与进气锥做碳化钨或陶瓷涂层，减缓冲刷磨损，延长风机检修周期。
Coating selection
| Duty | Coating | Thickness |
|---|---|---|
| Fine dust, moderate temperature | Al2O3-TiO2 | 0.20-0.35 mm |
| Coarse abrasive particles, impact | WC-Co (HVOF) | 0.15-0.30 mm |
| Hot gas with ash | Cr3C2-NiCr or YSZ depending on temperature | 0.20-0.40 mm |
| Wet corrosive gas | NiAl bond + Al2O3, sealed | 0.25-0.40 mm |
Where blades actually wear
Not uniformly. On a centrifugal fan handling dust, the leading edge of each blade and the blade-to-backplate fillet erode first, because that is where the particle stream turns and impacts at the highest angle. Coating the whole impeller at uniform thickness wastes money in the low-wear areas and under-protects the one place that matters. We map the wear pattern on the returned impeller and thicken the leading edges accordingly.
Balance after coating
An impeller running at 1,500-3,000 rpm cannot tolerate uneven coating mass. Blades are coated in matched pairs and the assembly is dynamically balanced after finishing, to ISO 1940 G6.3 or better. This step is not optional - an unbalanced coated impeller destroys its bearings within weeks.
Frequently asked questions
Can the impeller be coated without removing it from the fan?
Small impellers are removed. Large induced-draft fan rotors are usually sprayed in place with the rotor barred round by hand and local extraction, which avoids a crane lift.
How much life does the coating add?
In cement and biomass dust service, two to four times the life of an uncoated mild steel impeller is typical. On already-hardened wear plate the gain is smaller but still significant at the leading edges.
Does coating increase fan power consumption?
Negligibly. A 0.3 mm layer changes the profile far less than the roughness caused by erosion it replaces.
Further reading: HVOF vs plasma spraying.
