Cold Gas Spraying of Nickel-Titanium Coatings for Protection Against Cavitation

Area of Science:

• Materials Science
• Surface Engineering
• Tribology

Background:

• Cavitation erosion is a significant wear mechanism in hydrodynamic systems like turbines and pumps.
• Nickel-titanium (NiTi) shape memory alloys offer potential for cavitation-resistant coatings due to their damping properties.
• Cold gas spraying is a method for producing NiTi coatings.

Purpose of the Study:

• Investigate the phase transformation behavior of NiTi coatings produced by cold gas spraying.
• Assess the influence of process parameters on coating properties and deposition efficiency.
• Determine the presence of amorphous phases and oxides in NiTi coatings.

Main Methods:

• Cold gas spraying of NiTi coatings.
• Differential scanning calorimetry to analyze phase transformation.
• Microstructural analysis of sprayed particles and coatings.
• Investigation of near-surface zones for amorphous phases and oxides.

Main Results:

• Substrate temperatures during spraying were too low to activate the shape memory effect or pseudoelasticity.
• Oxidation was confirmed in the near-surface zones of particles, but no amorphous phase was detected.
• Local microstrain evolution indicated that substrate temperatures significantly impact deposition efficiency.
• Spray gun travel speed was identified as a key factor influencing substrate temperatures.

Conclusions:

• Cold gas spraying of NiTi coatings is feasible for cavitation erosion resistance.
• Process parameters, particularly spray gun travel speed, critically affect deposition efficiency through substrate temperature control.
• Oxidation, not stress-induced amorphization, is a primary concern affecting particle bonding and coating integrity.