Introduction:

• Refractories play crucial role in IMF industries
• Major degradation mechanism has been penetration and corrosion by molten metals or glass
• Methods to reduce penetration, wetting, and corrosive chemistry would improve refractory life

Advantages of Using High Density IR Heating:

• Compared to laser, can cover large areas
• Short wavelength irradiation
• Fast heating and cooling rates
• Very high temperatures attainable
• Potential for continuous processing

Results - Reduce Porosity for Improved Corrosion Resistance
Several Refractories Used in Initial Study

• All commercial sources
  
  • High alumina castable
    • 88% Al2O3-4% SiO2-4% Calcium aluminate-4% Mg; 3.2 g/cm3 with ~12% porosity
  • Aluminosilicate
    • 88% Al2O3-4% SiO2; 2.9 g/cm3 with ~16% porosity
• All were fired to ≥800°C prior to IR treatment and Non-IR treated materials fired to 1500°C for 1 h

Results - Surface Chemistry and Coatings

Two Types of AZS Glass Contact Refractories Tested

• Fused cast with 33% ZrO2 with 3-9% porosity (F.C. AZS-33)
• Cast and sintered with 20% ZrO2 with 17-20% porosity (C.S. AZS-20)
• ZrO2 slurry equivalent to 200 µm thick applied to surface and then IR treated

Cross-Sections of HDI Coated AZS

• Coatings much thicker than amount of ZrO2 painted on surface
• Bubbles within coating and at interface
• Trapped internal porosity
• Trapped gases in glass phase of F. C. AZS-33

Significant Mixing Occurs Between Applied
ZrO2 Coating and Underlying AZS

• Formation of fine ZrO2 dendrites in HDI affected region
• X-ray identified tetragonal ZrO2 on HDI coated surfaces
• Porosity (trapped gases and/or shrinkage)

Corrosion Testing

• Window glass plus 10 w/o NaCO3 mixture
• 1400°C immersion test
• 80 hour exposure times

Microstructure of AZS-33 After 80 Hour Test

• Considerable release of material from surface
• Boundary layer formation
• Retention of HDI fine dendritic structure

HDI Treatment of AZS Refractories

• Demonstrated that ZrO2-rich coatings could be produced on AZS refractories using HDI thermal treatments
• Mixing occurs between applied coating and underlying refractory
• Fine dendritic ZrO2 structure developed
• Porosity also generated
• Coatings help form boundary layer during glass contact