Delta Ferrite testing finds the percentage of delta phase iron inclusions in the test specimen. Excessive delta ferrite in the material may be detrimental to the material's properties. The point count...

Delta Ferrite testing finds the percentage of delta phase iron inclusions in the test specimen. Excessive delta ferrite in the material may be detrimental to the material's properties. The point count method is used for this test.

First, the test specimen is cross-sectioned, mounted, polished and etched. This reveals the grain structure of the specimen. Next, a photomicrograph is prepared, and a 10 x 10 grid is placed over the image. The technician inspects each intersection of the grid, scoring a point (or half a point) for each intersection where delta ferrite is found. The totaled score provides the percentage of delta ferrite in the specimen.

Typically several cross sections will be surveyed to provide the final test results. The photomicrograph is generally made at a magnification of 100 - 500x.

Delta Ferrite testing is performed to ASTM E562 Testing Method for Determining Volume Fraction by Systematic Manual Point Count.