Polishing is a mechanical process that removes surface imperfections and irregularities from titanium alloys to improve smoothness and flatness. The primary goals are to enhance surface quality, aesthetics, corrosion resistance, and biocompatibility.

Properties of Titanium

Pure titanium (99.5%) has:

Density (ρ): 4.5 g/cm³

Melting point: 1725°C

Thermal conductivity (λ): 15.24 W/(m·K)

Tensile strength (σb): 539 MPa

Elongation (δ): 25%

Hardness (HB): 195

Titanium has high chemical reactivity, low thermal conductivity, and poor grindability. Conventional abrasives are unsuitable; instead, ultra-hard abrasives like diamond or cubic boron nitride (CBN) are recommended. Polishing wheel speed should be 900–1800 m/min to avoid surface burns and micro-cracks.

Polishing Challenges

Thermal conductivity is 1/4 of nickel, 1/5 of iron, and 1/14 of aluminum.

Elastic modulus is ~half of steel, leading to deformation risks.

Surface rebound during machining is 2–3× higher than stainless steel.

Polishing Process for Titanium Alloys

Surface Pretreatment

Acid cleaning or electrolytic polishing to remove rust/oxidation.

Grinding

Mechanical or manual grinding to eliminate burrs and unevenness.

Polishing

Mechanical or chemical polishing for desired smoothness.

Sandblasting

Removes residual contaminants.

Cleaning

Rinsing to eliminate abrasive/polish residues.

Surface Treatment

Electroplating/anodizing for corrosion resistance or decoration.

Mechanical Polishing (Step-by-Step)

Rough Polishing: Titanium-specific hemp/wool wheel + coarse wax.

Medium Polishing: Coarse cloth/fine wool wheel + medium wax (removes scratches, adds shine).

Fine Polishing: Cotton wheel + fine wax (achieves high gloss, minor fabric marks remain).

Mirror Polishing: Bleached cotton wheel + mirror wax (eliminates marks for flawless finish).

Chemical Polishing

Uses redox reactions in chemical media to smooth surfaces.

Advantages: Independent of hardness/shape; no complex equipment needed.

Disadvantages: Difficult parameter control; requires precision for medical/dental applications.

Conclusion

Titanium alloy polishing is critical for surface quality and performance. Optimizing technical parameters and operator skill ensures compliance with industrial standards across aerospace, medical, and marine applications.