Internal Stress of Titanium-Based Nitride with Penetration Depth and Surface Roughness by sin²ψ Method Using HR-XRD

Area of Science:

• Materials Science
• Surface Engineering
• Mechanical Engineering

Background:

• Titanium nitride (TiN) coatings are crucial for enhancing material properties.
• Internal stress is a key factor influencing the mechanical performance of coatings.
• Optimizing measurement techniques for internal stress is essential for material development.

Purpose of the Study:

• To optimize a test method for measuring internal stress in titanium-based nitride coatings.
• To investigate the impact of carbon gradient layer ratios on mechanical properties via internal stress.
• To validate the optimized internal stress measurement technique for varying surface roughness and coating thicknesses.

Main Methods:

• Optimized internal stress measurement using High-Resolution X-ray Diffraction (HR-XRD) by adjusting penetration depth.
• Investigated the effect of surface roughness (0.01 Sa, 0.02 Sa, 0.03 Sa) on internal stress measurements.
• Applied the optimized method to carbon-doped TiZrN coatings deposited on SUS 304, varying coating thickness (0.5 μm, 1 μm, 2 μm) and using laser carburization.

Main Results:

• Internal stress gradient remained constant regardless of penetration depth, indicating substrate independence.
• The measurement method proved valid for coatings with surface roughness up to 0.03 Sa.
• Compressive internal stress in carbon-doped TiZrN coatings increased significantly with higher carbon gradient layer ratios, reaching -1687 MPa at 0.5 μm thickness.

Conclusions:

• An optimized, reliable test method for internal stress in TiN coatings was established.
• The ratio of the carbon gradient layer is a critical factor in enhancing the mechanical properties of TiZrN coatings.
• Laser carburization effectively increases internal stress, leading to improved mechanical performance in carbon-doped TiZrN coatings.