Glow discharge sputtering technology and apparatus for microstructural preparation of metallic materials

Abstract

Authentic and efficient preparation of microstructures over large surface areas of materials is crucial for accurate characterization of material properties. Traditional microstructural preparation techniques, such as mechanical polishing, chemical etching, and ion beam milling, suffer from limitations including surface damage, complex procedures, and low efficiency. In contrast, glow discharge sputtering (GDS) operates in a high-pressure argon atmosphere (several millibars) and utilizes a wide-angle, low-energy argon ion beam to achieve uniform large-area sputtering with minimal material damage and high preparation efficiency. More importantly, the sputtering yield differences at grain/phase boundaries in GDS lead to selective sputtering behavior, which directly reveals the material's original microstructure, thereby eliminating the two essential steps of polishing and etching in traditional metallographic preparation. Commercial GDS instruments are exclusively designed for chemical composition analysis, lacking microstructural preparation capabilities. Furthermore, their restricted anode cylinder dimensions prevent them from meeting large-area preparation requirements. This study first employs numerical simulations to analyze glow discharge cathode sputtering behavior, confirming GDS's capability to preserve the material's original microstructural characteristics. Building upon this foundation, we designed and constructed a dedicated GDS apparatus for microstructural preparation, incorporating a successive approximation control algorithm to stabilize the glow discharge process. In practical applications, the integration of GDS with electron backscatter diffraction (EBSD) enabled three-dimensional reconstruction and visualization of GH4169 polycrystalline superalloy grains, revealing their three-dimensional morphology and spatial distribution. Additionally, GDS demonstrates versatility across various materials and characterization techniques. It significantly enhances microstructural image quality in EBSD, metallographic, and backscattered electron (BSE) imaging for materials including martensitic heat-resistant steel, T2 copper, and GH4096, effectively replacing polishing and etching in certain applications. This establishes GDS as an innovative approach for microstructural preparation in metallic materials.