Back to Failure Analysis Learning Center  Back to Learning Center Home Page |
A small surface indication as determined by failure analysis service performed by MSi. |
|
| Keywords: Failure Analysis Service, Linear Defect Indication, Metallurgy Experts, Metallographic (Microstructure) Examination, Failure Analysis Lab, Metal Test Lab, Pre-existing Internal Steel Defect, |
| BACKGROUND |
One (1) cold drawn and machined part exhibiting a linear defect indication on the machined ID surface was submitted to our laboratory for a metallurgical failure analysis service investigation. Our metallurgy experts were requested to determine the source cause of the ID surface defect indication. The material identification is shown in the table below. |
| |
| SAMPLE IDENTIFICATION |
| Part Description |
Heat No. |
HR Size |
CD Size |
Grade |
| Machined Part |
|
|
|
C-1215 |
|
| |
| PERFORMED TESTING |
Scanning Electron Microscopy (SEM) Examination
Metallographic (Microstructure) Examination
Chemical Analysis
|
| |
| CONCLUSIONS |
1. Based upon the opinion of our failure analysis lab and the performed examinations, it is our opinion the ID surface of the part contained a faint, intermittent, tool mark that was induced during the machining operation.
2. No evidence was observed of a pre-existing internal steel defect or inclusion stringer on the ID surface that could have caused the defect indication.
3. The microstructure as determined by the metal test lab was typical of AISI 1215 steel.
4. The chemical composition was typical of AISI 1215 steel. |
|
| |
| SUMMARY of TEST RESULTS |
| |
| Scanning Electron Microscopy Examination |
1. SEM examination of the ID surface revealed a faint, intermittent, linear surface defect indication along the .234” diameter ID surface. (See arrows in Photos 1 - 2).
2. Examination at higher magnification showed evidence of disturbed metal, most likely from the machining tool (see Photos 3 – 4). No evidence was observed of a pre-existing internal steel defect or inclusion stringer on the ID surface.
|
|
| |
 |
| Photo 1: Submitted part with surface defect indication on
the ID surface, denoted by the yellow arrow. 1.5X |
| |
 |
| Photo 3: Close-up view of linear defect indication denoted
by the yellow arrow in Photo 2. 165X |
|
|
 |
| Photo 2: SEM image showing the faint linear defect
indication on the machined ID surface. 10X |
| |
 |
| Photo 4: Higher magnification view of Photo 3 showing a
tool mark from the machining operation. 1350X |
|
|
| |
| Metallographic Examination |
1. A transverse section removed from the region containing the ID surface defect indication confirmed the presence of a tool mark that was induced during the machining operation. (See arrow in Photos 5 - 6)
2. No evidence was observed of an abnormal inclusion content or any other detrimental internal conditions that could have caused the defect indication.
3. The microstructure consisted of pearlite and grain boundary cementite in a matrix of ferrite, typical of AISI 1215 steel. |
| |
 |
| Photo 5: Mag: 200X; Etchant: None
Cross-sectional view of stress crack initiating from .037” deep
seam (at arrow).
|
|
|
 |
| Photo 6: Mag: 500X; Etchant: None
High magnification view of seam profile showing decarburization
and dispersed oxides. |
|
|
| |
| Chemical Testing |
1. Chemical testing revealed the sample classified as AISI 1215 steel.
2. The results are shown in Table 1 attached. |
| |
| Table 1 – Chemical Testing* |
| Element |
Results |
| Carbon |
.06 % |
| Manganese |
.96 |
| Phosphorus |
.05 |
| Sulfur |
.31 |
| Silicon |
.02 |
| Nickel |
.03 |
| Chromium |
.03 |
| Molybdenum |
.01 |
| Copper |
.06 |
|
| |
| * Testing performed in accordance with ASTM E415. |
| |
