Thermal Barrier Coatings (Case Study)

• The barrier coat reduces the direct effect of temperature by reducing heat transfer caused by conduction, convection & radiation. Thus the base material retains properties which it could have lost at high temperature exposure.
• The final coating material is normally a ceramic oxide. Industry uses are mostly limited to Stabilized zirconia( Zirconia changes phase at around 1000 deg C) or Alumina.
• All ceramic oxides are oxygen transparent hence a oxidation resistant bond coat is provided.
• Coatings can peel off at high temperature due to variation in co-efficient in thermal expansion. Hence depending on base material a graded CTE matched material is applied.

We have carried out repairs on Roof jackets of copper blast furnace. The jackets had following properties

• MOC copper.
• Wear due to high temperature corrosion by SO4 gases and splashing of molten copper on roof jackets at 1240 deg C. observed wear was around 15-20mm reduction in thickness of copper jacket.
• The jackets are water cooled.

Solution: Multi layer coatings of bond coat + top coat + sealant are applied. We carried out the job by ARC spray Aluminium bronze + MCRAlY alloy + Rod sprayed Alumina + Sealant suitable up to 1600 dg C.