Numerous fuel nozzle clips from RVs and marine applications were found to be failing unexpectedly. The failures all had a characteristic brittle fracture appearance and visibly indicated no plastic deformation. A sample of the failed fuel clips is shown in Photograph A.
Photograph A Overall view of failed fuel nozzle clips.
Failures of the fuel clips were also found to occur in the clip shoulder as shown in Photograph B.
Photograph B Shoulder failure of fuel nozzle clips.
These 17-7 PH stainless steel clips were also observed to exhibit surface pitting as shown in Photograph C.
Photograph C Surface pitting on failed fuel clip.
Close-up examination revealed superficial corrosion around the fracture and on the clip surface. The corroded surface near the fracture is shown in Photograph D.
Photograph D Close-up view of surface corrosion on failed fuel clip.
An overall view of the fractured clip in Photograph E illustrating corrosion on the surface of the failed nozzle clip near the fracture surface.
Photograph E Failed fuel nozzle clip with corrosion near the clip fracture.
The clip fracture surface is shown in Photograph F.
Photograph F Close-up view of nozzle clip fracture surface.
The fracture surface appeared grainy and exhibited no evidence of ductile fracture. The fracture surface of all of the clips examined also exhibited a grainy, non-ductile fracture as shown in Photograph G.
Photograph G Grainy fracture surface of failed stainless steel nozzle clip.
SEM examination revealed, even at low magnification, the intergranular fracture pattern shown in Photograph H.
Photograph H Fracture surface indicates intergranular fracture.
A close-up view, at a magnification of 500x, is shown in Photograph I.
Photograph I View of intergranular fracture on failed nozzle clip.
Metallographic polishing of one of the clips was conducted and the resulting polished surface is shown in Photograph J.
Photograph J Scanning electron micrograph (mag 300x) showing intergranular fracture of polished metallographic specimen.
Energy dispersive spectroscopy revealed, as shown in Figure 1, a very large concentration of chlorine (Cl).
Figure 1 View of intergranular fracture on failed nozzle clip.
As a result of this investigation it was determined that the 17-7 PH stainless steel nozzle clips had been improperly heat treated and therefore were rendered sensitive to intergranular stress corrosion cracking.