Sand erosion resistance improvement and damage mechanism of TiAIN coating via the bias-graded voltage in FCVA deposition

Titanium aluminum nitride (TiAIN) coatings were deposited on Ti6A14V alloy substrates using a filtered cathodic vacuum arc (FCVA) deposition method with bias-graded voltage ranging from -50 V to -200 V and constant bias voltage (-50 V, -125 V, and -200 V). The microstructure and mechanical properties of these coatings were investigated and compared. Sand erosion resistance at 30 degrees and 90 degrees was evaluated using sandblasting equipment. The coating deposited at a constant bias voltage of -200 V had the highest average hardness of 32.47 GPa. The bias-graded coating had a similar average hardness (32.08 GPa), but lower internal stress (-2.66 GPa) and considerably higher adhesion strength (44.03 N) than the constant-bias coatings. For both erosion angles (30 degrees and 90 degrees), the erosion rates of the constant-bias coatings increased with increasing bias voltage. In general, the erosion rates of the bias-graded coating (0.014 and 0,013 mg/g at erosion angles of 30 degrees and 90 degrees, respectively) were significantly lower than that of the constant-bias coatings. Bias-graded deposition is an effective method of improving the erosion resistance of coatings. The erosion mechanism of the coatings is coating chipping. The excellent erosion resistance of the bias-graded TiAIN coating is attributed to the high hardness and low internal stress of this coating.