Effect of Pulsed Biasing on the Droplet Formation and the Properties of Cylindrical Cathodic Arc–Grown Erosion-Resistant TiN Coatings

Abstract

For the past few decades, cathodic arc–grown erosion-resistant coatings have become very popular and are widely used in aerospace applications to significantly enhance the service life of compressor blades. Though the coatings improve life, the concentrations of defects and stressed areas on the surface dictate the end life of the component. Therefore, in the present study, an attempt was made to minimize the defect area fraction along with the residual stresses in cylindrical cathodic arc–grown mono- and multilayer TiN coatings by optimizing pulsed bias voltage parameters such as duty cycle and magnitude of bias voltage. The effect of pulsed biasing and coating configuration on the physical, mechanical, and erosion properties of the TiN coatings was studied systematically. Within the monolayer TiN coating, the samples grown at −500 V pulsed bias and 40% duty cycle had the best properties with about 50% enhancement in erosion resistance. These coatings were also found to exhibit the lowest residual stress, good adhesion, and moderately higher hardness. Further, the TiN coatings grown in a multilayer configuration (TiN_E-450/TiN_E-350) had the best erosion resistance.

Keywords:

• Pulsed bias
• cathodic arc deposition
• erosion resistance
• TiN
• droplet formation

Acknowledgements

The authors thank C. Puneet for his assistance with the XRD and residual stress analysis, K. Jalamani for her assistance in characterization studies, and the Indian Airforce for supplying the TiN-coated helicopter compressor blade. The authors gratefully acknowledge the permission granted by the director of ARCI to publish this work.