INFLUENCE OF THE SUBSTRATE BIAS VOLTAGE ON FRETTING FATIGUE BEHAVIOR OF CrN FILM DEPOSITED ON Ti-6Al-4V ALLOY

An experimental investigation was conducted to examine the fretting fatigue behavior of physical vapor deposition-coated CrN film deposited on Ti-6Al-4V specimens contacted on both sides with pads of the same material. Behavior against the CrN-coated specimens was characterized through the determination of fretting fatigue strength up to 10(7) cycles. Fretting damage of specimen surface was characterized by SEM and surface profilometer. The experimental results from the S-N tests indicate that the CrN coating is effective to improve the fretting fatigue strength until about 10(6) cycles, but over 10(6) cycles, the strength is lower than that of uncoated specimens. The enhanced fretting fatigue resistance can be attributed to the improved hardness of the CrN film due to change of bias voltage during the film deposition. It has also been concluded that below and about 10(6) cycles, there is smaller influence of bias voltage on fatigue strength, whereas, over 10(6) cycles, fatigue strength is clearly changed by bias voltage as well as contact pressure.