Potentials%20of%20Post-Processing%20Thermal%20Spray%20Coatings%20for%20Tribological%20Applications

1
Potentials of Post-Processing Thermal Spray
Coatings for Tribological Applications

• R. Ahmed
• Heriot-Watt University, United Kingdom

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Typical Post-treatments for Thermal Spray Coatings

• Annealing/Austempering
• Laser Remelting
• Hot Isostatic pressing

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Annealing / Austempering
Post-Treatment

• Improved Hardness and Sliding Wear Resistance
• Low Cost
• Control of Residual Stress
• USEFUL FOR LOW STRESS SLIDING WEAR APPLICATIONS
• Need for correct Coating Substrate Pair
• Marginal Pore Modification and Metallurgical
  Bonding

4
Laser Remelting

• GOOD FOR CORROSION AND SLIDING WEAR RESISTANCE
• Good Depth Control of Treatment
• Substrate Material Not Critical
• Good for Eliminating Porosity
• Promote Metallurgical Bonding
• No Control of Residual Stress
• Not Good for Lubricated Contacts

5
Hot Isostatic Pressing

• IDEAL FOR HIGH STRESS TRIBOLOGICAL APPLICATIONS
• Improves Impact, Delamination,Abrasion and
  Fatigue Resistance
• Ideal for Metallurgical Bonding
• Good Control of Residual Stress
• Improves Product Cost Effectiveness
• Attenuate Coating Anisotropy
• Requires a Correct Coating Substrate Pair

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POTENTIAL IMPROVEMENTS Post Treatment

• Promotion of the metallurgical bonding at
  splat/splat and splat/substrate level to improve
  the adhesive and cohesive strength.
• Elimination of porosity and microcracks to avoid
  stress concentrations within the coating
  microstructure.
• Amorphous to crystalline and other phase
  transformations.
• Generation of uniform compressive stress in the
  coating by appropriate control of heat transfer
  for a given coating and substrate material.
• Attenuation of the coating anisotropy, to obtain
  near homogenous material properties.