A company induction heat-treats large round steel components. Field experience with these parts suggested that a manufacturing problem could exist that led to premature failure. The company had no way to evaluate product quality internally, and the components exhibited no problems that were visible to the naked eye, so another technique needed to be used.
Several inspection options exist that could be used on this part. The ideal tool was portable, and relatively inexpensive. This method needed to find defects in ferrous parts when they lie at, or even slightly below, the surface. Magnetic particle inspection was selected based on cost and speed of inspection. A portable contour probe was used with fluorescent particles, and the inspection was then performed under UV-A (black light). Indications from defects were clearly visible directly on the surface of the part.
While there were no problems on the test piece that were visible to the unaided eye, the magnetic particle indications, which fluoresce under UV-A light, are highlighted in the second image.
A poor induction heat-treating setup resulted in a multitude of cracks running along, and across the machined grooves. Defects that would have gone undetected were located using magnetic particle inspection.
A complete kit could be purchased for less than $1,200, allowing for regular internal quality checks.