Positron Annihilation Spectroscopy Study of Metallic Materials after High-Speed Cutting

Area of Science:

• Materials Science
• Mechanical Engineering
• Surface Engineering

Background:

• High-speed cutting often generates a white layer on machined surfaces, negatively impacting mechanical properties.
• The white layer's properties are linked to its material structure and cutting-induced defects.
• Research on atomic-scale defects within the white layer is limited.

Purpose of the Study:

• To investigate the influence of cutting parameters (feed rate, cutting speed, cutting depth) on atomic-scale defects in GCr15 steel during high-speed cutting.
• To characterize the types and distribution of defects in the white layer and subsurface regions.

Main Methods:

• Utilized positron annihilation spectroscopy (PAS) to study atomic-scale defects.
• Analyzed GCr15 steel samples subjected to varying high-speed cutting parameters.

Main Results:

• Positron annihilation studies revealed defects characteristic of plastically deformed or tempered carbon steel, along with vacancy cluster components.
• The quantity of vacancy clusters varied with changes in cutting parameters.
• Significant microstructural alterations, including phase transformations, deformation, and thermal impacts, were observed in the subsurface region up to 1 µm.
• No single type of atomic-scale defect dominated the subsurface region.

Conclusions:

• Cutting parameters significantly influence the type and quantity of atomic-scale defects in the white layer of GCr15 steel.
• The white layer and its subsurface region exhibit complex microstructural changes due to combined mechanical and thermal effects during high-speed cutting.
• Understanding these defects is crucial for predicting and improving the performance of machined components.