Parameters Optimization of Metallographic Examination of Contamination Layer on TC4 Titanium Alloy Surface

The metallographic examination parameters of TC4 titanium alloy surface contamination layer were evaluated by orthogonal experiment and technique for order preference by similarity to ideal solution (TOPSIS). The optimal polishing process and etchant were selected according to the evaluation results. The results show that the influence degree of polishing process parameters on sampling quality was pressure > polishing machine speed > polishing time, the optimal combination of polishing process parameters was grinding prototype speed 300 r·min^-1, polishing time 1 min, pressure 30 N. The optimal etchant was 2% (volume fraction) HF(mass concentration 40%～42%)+4% (volume fraction) HNO₃(mass concenrtation 65%~68%)+H₂O(margin), and then 2% (mass concentration) NH₄HF₂ aqueous solution.