Glass Film Formation on GOES Surface during High-Temperature Annealing: The Mechanism with Amorphous Phase Formation

Area of Science:

• Materials Science
• Metallurgy
• Surface Engineering

Background:

• Ceramic insulation coatings, specifically glass films, are critical components in grain-oriented electrical steel (GOES) used in transformer cores.
• The formation and properties of these glass films directly impact the performance and efficiency of electrical steel.

Purpose of the Study:

• To investigate the formation mechanism and structural characteristics of a glass film on GOES.
• To analyze the interaction between GOES with copper content and a magnesium oxide (MgO) coating during high-temperature annealing.

Main Methods:

• High-temperature annealing of GOES with MgO coating in a H2/N2 atmosphere.
• Structural analysis using X-ray diffraction (XRD), glow-discharge optical emission spectroscopy (GDOES), scanning probe microscopy (SPM), and scanning electron microscopy (SEM).
• Thermal analysis via differential scanning calorimetry (DSC) and thermodynamic calculations.

Main Results:

• Successfully formed a glass film on GOES containing 0.5 wt.% Cu through interaction with an MgO coating during annealing up to 1100 °C.
• Identified crystalline (MgFe)2SiO4 and amorphous Fe-based solid solutions as the primary phases within the formed glass film.
• Elucidated a multi-stage mechanism governing the glass film formation on the GOES surface during high-temperature processing.

Conclusions:

• The study provides a detailed understanding of the glass film formation process on GOES, crucial for optimizing electrical steel production.
• The identified phases and formation mechanism offer insights for developing advanced ceramic insulation coatings for improved transformer efficiency.
• This research contributes to the field of materials science by detailing the complex interfacial reactions during the annealing of coated electrical steels.