Experimental Design Approach to Development of a CVD ZrN Coating

Abstract
A design of experiments (DOE) approach has been used for the study of CVD ZrN coatings on cemented carbide substrates. DOE maximizes information gained from a set of experiments through statistical methods of design and analysis. A full factorial matrix of twenty experiments was designed using the variables (A) pressure, (B) temperature, (C) H₂/ZrCl₄ and (D) N₂/ZrCl₄. Pressure ranged from 100 to 300 torr, temperature from 900 to 1050 °C, H₂/ZrCl₄ from 20 to 60 and N₂/ZrCl₄ from 5 to 25. The response for deposition rate is compared with theoretical prediction based on thermodynamic modeling of the system. A normal probability distribution was used to identify the variables that had a significant effect on deposition rate. These were found to be (B) temperature and (C) H₂/ZrCl₄. Interaction plots for (B) and (C) generated by the software clearly show this effect. These results are in agreement with the thermodynamic analysis and are similar to results for TiN coating. Other responses such as color, surface morphology, texture, adhesion and friction are reported.