The use of plasma cladding technology to strengthen the surface of PDC drill bits is an effective means to improve their wear resistance, impact resistance and corrosion resistance.
1. Preparation stage
(1) Determine the cladding material
- Commonly used cladding materials:
- Cobalt-based alloy: high wear resistance and corrosion resistance.
- Nickel-based alloy: resistant to high-temperature oxidation and chemical corrosion.
- Iron-based alloys: cost-effective and suitable for medium wear resistance requirements.
- Ceramic particle reinforced alloys: e.g. WC (Tungsten Carbide), TiC (Titanium Carbide), etc. for very high wear resistance requirements.
(2) Determination of cladding area
- The fusion cladding of PDC drill bits usually targets:
- Flank part: to enhance wear resistance and reduce friction and cutting loss.
- The surface of the carcass: to enhance the overall corrosion and impact resistance.
(3) Surface pretreatment
- Clean the cladding area to remove oil, oxides, coatings and impurities.
- Mechanical grinding or sandblasting treatment to increase the roughness of the surface and improve the bonding of the fused cladding layer with the substrate.
2. Implementation of the cladding process
(1) Setting up plasma cladding equipment
- Equipment composition:
Plasma welding gun, powder feeder, automated plasma welding machine, etc..
- Set the key parameters:
- Arc current and voltage: select according to the material to be coated, generally in the range of 100-300A.
- Heat input: adjust to control the substrate deformation and dilution rate.
- Powder feeding rate: usually in the range of 10~50g/min to ensure the uniformity of the cladding layer.
(2) Execution of cladding
- The cladding process:
1. plasma arc start, the formation of high-temperature melting pool.
2. Through the powder feeding system, the powder material is sprayed into the molten pool and metallurgically bonded with the substrate.
3. according to the shape of the drill bit, along the set path for uniform cladding, to ensure that there is no leakage of cladding or over-melting.
- Control thermal influence: avoid overheating or deformation of the PDC drill bit substrate by adjusting the plasma arc parameters and cooling method.
(3) Cooling treatment
- Natural cooling or adopt controlled speed cooling method to avoid cracks caused by thermal stress.
3. Post-treatment stage
(1) Inspection of cladding quality
- Appearance inspection: Observe whether the cladding layer is uniform, free of cracks and air holes.
- Performance testing: measure the hardness, thickness (usually in 0.5 ~ 3mm), bonding strength and other indicators.
- Non-destructive testing: Use ultrasonic or X-ray testing to troubleshoot internal defects.
(2) Finishing
- If the surface is rough after fusion cladding, turning or grinding treatment is required to meet the size and shape requirements of PDC drill bits.
(3) Performance optimization
- Heat treatment: quench or temper the fused cladding layer if necessary to further optimize its organizational properties.
4. Precautions
1. Avoid overheating damage
- During plasma cladding, the heat input should be strictly controlled to avoid thermal damage to the PDC insert and the substrate.
2. Material matching
- The cladding material should be matched with the material of the PDC bit substrate to ensure the bonding strength and performance consistency.
3. Environmental control
- As far as possible in a low humidity or protective gas environment to avoid oxidization affecting the quality of the cladding.
This process can be used to enhance the performance of new PDC bits as well as to repair worn bits.
Post time: Jan-09-2025