Page 29 - Handbook of Materials Failure Analysis
P. 29
3 Case Studies 21
O
Cr
Area-A
Si Au Cl
Fe
Ni
0.80 1.60 2.40 3.20 4.00 4.80 5.60 6.40 7.20
(a)
Area-B
Al Si
Ca
C O
Au
Cr Fe
Cl
0.80 1.60 2.40 3.20 4.00 4.80 5.60 6.40 7.20
(b)
FIGURE 1.17
EDS elemental microanalysis spectra obtained on selected areas within the filled pits (a) Area-
A and (b) Area-B (see Figure 1.16).
exposed surface. Growth of chromium oxide layer up to a critical thickness leads
eventually to crack initiation, due to the imposed tensile stresses, which may result
in flaking and removal of oxide layers and exposing the fresh metal surface continu-
ing the oxidation cycle.
3.2.4 Discussion and conclusion
Failure investigation of an austenitic stainless steel grid, operating in a shell-and-tube
heat exchanger of a petrochemical industry, was a result of a series of synergistic
degradation mechanisms attributed to oxidation and SCC. These mechanisms
assisted to severe surface pitting and multiple transgranular cracking, contributing
to adverse effects on the structural integrity of the grid and leading to excessive dete-
rioration, fragility/brittleness and subsequently gross metal loss.
