Non-contact inspection
of coatings and grinding burn

Testing systems for grinding burn & coating inspection

Many components are case hardened or nitrided to reduce wear. Others are provided with coatings or ground during the finishing process. All these processes require quality control with testing equipment or testing facilities. However, the materialographic analysis that is often carried out takes a long time and is only carried out on random samples because the sample is destroyed by the test. A fast, non-destructive alternative to this is photothermics.

Coating inspection in a nutshell

Typical applications of coating testing equipment are: Coating thickness measurement, hardening depth classification, nitriding depth classification, grinding burn detection, adhesion defect detection, hidden corrosion detection, crack detection, weld tracking.

The duration of a measurement depends very much on the level of detail required. A few seconds to many minutes are possible.

How coating inspection works

The photothermal method of our testing systems is based on periodic surface heating by means of laser light. The modulated heat flows from the surface into the interior of the component, whereby the heat flow is influenced by the material properties and the specimen geometry. An infrared detector continuously records the radiation intensity-proportional signal of the surface, which is analysed by a lock-in amplifier according to amplitude and phase. By means of calibration measurements, the phase can be linked to certain material parameters, such as hardness or layer thickness. For this purpose, both photothermal measurements and a subsequent destructive test of representative reference samples are required.