Page 13 - Handbook of Materials Failure Analysis

3 Case Studies 5

Table 1.1 Review of Characteristic Failure Mechanisms Activated in Chemical
Process Environments Together with Some Relevant References
Some
Relevant
References
Failure Mode (Addressing
Main Failure Environmental (Typical Failure the Failure
No. Mechanism Condition(s) “Signature”) Mechanism)
1 Creep damage Long-term heating, Spheroidization of [4,5,20–22]
stress (internal carbides/void
pressure) formation, growth
and coalescence
2 Thermal fatigue Thermal cycling and/ Macroscopically [2,23]
and high- or high-temperature brittle fracture—
temperature stress cycling progressive crack
fatigue markings—oxidized
surface
3 Hot oxidation/ Chemical attack Oxidation and [16–18]
corrosion/ (e.g., chlorides, corrosion scale
erosion sulfides, CO 2 )/high- deposits/metal loss
corrosion temperature or dissolution
oxidation
4 Hydrogen Chemical attack by Brittle cracking, [19]
induced H 2 S, H 2 , atomic microcracking at
cracking (HIC) hydrogen diffusion areas of entrapped
nonmetallic
inclusions
5 Stress- Chemical attack Delayed brittle [8,9,12,13,24]
corrosion (e.g., chlorides, fracture/
cracking (SCC) sulfides) and residual intergranular or
or applied tensile transgranular
stress cracking
6 Corrosion Chemical attack/ Surface pitting and [15]
fatigue (CF) pitting—cyclic fatigue crack
loading nucleation
7 Microstructural Thermally induced Cr-depletion, [24–27]
degradation, degradation and carbide precipitation
sensitization, phase and grain boundary
and transformations due sensitization,
embrittlement to long-term σ-phase formation
overheating ( 600-
900 °C)

of series of steel tubes welded circumferentially. Systematic data collection over
1 year of service indicated that failures occurred approximately every 15 days on
average and situated either at curved areas of the tubes or in the vicinity of circum-
ferential welded joints. The detailed metallurgical examination followed on failed
tubes indicated that pipeline damage caused as a consequence of creep rupture.