The wear of highly stressed metal components, such as Bearings, shafts and railway wheels, is drastically reduced by hardening the surface layers. A common process for this is induction hardening, in which a hard layer is created on the outside by electrical heating and subsequent hardening, while the base material remains in the initial less hard state. The exact depth of the cured layer is decisive for defect susceptibility and durability and must be carefully monitored. With the usual methods for the determination of the depth of hardening samples must be taken from production and placed in critical positions cut be used to determine the depth of cure on the cut surface. It is often necessary to polish and etch beforehand to make the depth of hardening visible; hardness indentations are set for absolute values. In any case, the component must be destroyed for analysis, at the same time only the information of this tested sample is available at the selected interface. For large single parts, such as bearings or shafts for hydroelectric or wind power plantsdestructive tests are not possible.
One without contact and a non-destructive technology, ideal for determining the hardening depth of several millimeters and under development at RECENDT Laser ultrasound. Ultrasounds are generated directly on the sample surface using high-energy laser pulses lasting a few nanoseconds. With a second laser beam from an interferometer, the reflected ultrasonic waves are recorded over a wide range of frequencies and evaluated online. With the two laser beams, large areas of the surface can be scanned and converted into sectional images showing the depth of cure! With between 10 and 100 laser measurement points per second, this process is also very fast and can be fully automated.
through the benefit Due to the non-contact nature of laser ultrasound, this technology can be used early in the manufacturing process after curing, even when components are still hot and wet. In addition, an inspection of each individual part is possible online, so the Quickly optimized hardening process it can be and one uninterrupted quality control it’s possible.
Original content from: Research Center for Non-Destructive Testing GmbH transmitted by news aktuell