| Industry: |
Cement Manufacturing Plant |
| Specimen Description: |
310SS Refractory Anchors |
| Material: |
310 Stainless Steel |
| Environment: |
High-Temperature Flue Gases |
| Background: |
Type 310SS refractory anchors were failing due to
complete fracture, resulting in loss of refractory insulation in a cement
kiln. |
| Time in Service: |
Unknown |
| Findings: |
As-received 310SS refractory anchors were grayish
and scaley but otherwise showed no significant surface scale resulting
from the high temperature service. The anchor fractures were brittle
appearing with no macroscopic ductility. Metallographic examination of
the anchor fractures revealed intergranular fracture, intergranular cracking
and grain dropping, suggestive of polythionic acid
stress corrosion cracking (PASCC) from exposure to a condensed aqueous phase containing oxygenated
sulfur compounds. The PASCC suggested that the anchors were cracking
during downtimes. No significant oxidation or subsurface sulfidation
was observed. |
