Adjustment, Improvement, and Control of a Physical Vapor Deposition (PVD) Process Using Quantitative Depth Profile (QDP) Analysis

Significance of the Topic

Physical vapor deposition (PVD) coatings such as chromium nitride (CrN) are widely used to enhance wear resistance of cutting tools and components. However, inherent porosity limits their corrosion resistance. Accurate measurement of coating thickness, composition and homogeneity is essential to optimize performance, extend tool life and ensure consistent product quality.

Objectives and Study Overview

This study employs quantitative depth profile (QDP) analysis by glow discharge optical emission spectrometry (GD-OES) to evaluate and improve PVD processes. Key objectives include:

• Assess single CrN coatings deposited at low temperature (LT) and high temperature (HT).
• Characterize electroless nickel-phosphorus (NiP) interlayers of varying thicknesses (7, 12 and 22 µm).
• Investigate combined CrN/NiP multilayer systems for enhanced corrosion protection.

Methodology and Instrumentation

Coating systems were analyzed using GD-OES QDP, providing rapid elemental depth profiles and computed layer thicknesses within minutes. The main instrumentation included:

• LECO GDS Series GD-OES spectrometer.
• QDP software for real-time data acquisition, profile visualization and automated report generation.

Key Results and Discussion

Single CrN Coatings:

• LT process yielded ~2.92 µm thickness with Cr content ~77 wt% and N ~21.9 wt%; excellent reproducibility and stoichiometry near unity.
• HT process produced slightly thicker coatings (~3.31 µm) with similar composition; reproducibility marginally lower than LT.

Single NiP Coatings:

• Actual thicknesses exceeded targets: 7 µm → 8.6 µm, 12 µm → 15.7 µm, 22 µm → 25.7 µm.
• Nickel distribution remained uniform (~92 wt%), while phosphorus profiles showed fluctuations, especially in thinner layers.
• Increased NiP thickness enhanced diffusion into the steel substrate.

Multilayer CrN/NiP Systems:

• CrN LT and HT layers on NiP interlayers exhibited clear interfaces and maintained homogeneity.
• CrN thickness on NiP varied consistently with standalone processes.
• Interface resolution highlighted diffusion phenomena; thicker NiP promoted deeper element migration.

Benefits and Practical Applications

• Rapid quality control of single and multilayer coatings in routine production.
• Accurate monitoring of process deviations and adhesion quality.
• Enhanced corrosion resistance through optimized NiP/CrN layering.
• Support for research and development of novel coating architectures.

Future Trends and Opportunities

• Integration of GD-OES in-line for real-time process control.
• Advanced automation of data processing and customized reporting.
• Extension to complex multilayer and gradient coatings for tailored functionalities.
• Combination with complementary methods (e.g., microscopy, XPS) for comprehensive surface analysis.

Conclusion

GD-OES QDP analysis proves to be a rapid, reproducible and highly informative technique for characterizing PVD coatings and multilayer systems. Its ability to deliver precise thickness, composition and interface insights makes it indispensable for both industrial quality assurance and research development.

References

No external references cited.