Oxide Detection in Aluminum Casts
The goal of this MPI project is to determine viable options for the non-destructive evaluation of oxide levels in aluminum cast components. The approach involves a review of existing NDE techniques and an overview of their effectiveness in detecting oxides. Tests were conducted using various NDE techniques on controlled and industry-supplied samples.
If the NDE technique identifies porosity entrained in the samples along with oxides, the HIP (Hot Isostatic Pressing) method can be used to remove most porosity from the aluminum cast components. This procedure is conducted by applying heat and significant pressure to the aluminum part. The advantage to HIP treating the samples is that with the porosity removed, we can be sure that the NDE tests will only be sensitive to the detection of oxides. When testing of these samples was completed, we destructively tested some HIPed and un-HIPed samples and concluded that there is in fact no significant porosity in the HIPed parts.
Ultrasonic phase velocity profile of HIPed (left column) versus un-HIPed (right column) aluminum cast sample
X-Ray
X-Ray testing has been applied to large oxide plate samples. The HIP process was an important aspect of the X-Ray testing. By HIPing the samples we can be sure that any information seen with X-Ray inspection is in fact due to oxides and not porosity. For instance, the un-HIPed sample reveals holes that are visible on the left side, most of which are not surface breaking flaws. The excellent ability of X-Ray to determine porosity makes these flaws obvious. The HIPed sample still has a few visible subsurface flaws that do not break through the surface. Since this plate has been HIPed, it is very likely that the visible flaws are in fact oxides. This analysis suggests that X-Ray is a potentially viable test platform for the detection of oxides in aluminum cast components.
Last modified: September 10, 2007 11:31:59