With most of the chip detectors I come by, they worked only on ferrous materials, and of size approximately 100µm and more. As even the electric ones work on principle of collecting chips with magnetic field, and then shorting an electric circuit inside with that said chip. If the chip is not ferrous (coatings, light alloys, polymers etc.) or too small - it will not indicate.
Better chip monitoring systems include spectrography and lubricant flow monitoring... known in aviation industry by common name: "expensive".
Unfortunately in a scenario of protective coating failure it can lead to relatively fast destruction of the gear teeth, although producing small debris - around 20-40µm - for such case only constant gear monitoring system that includes magnetic field monitoring could pick such failure in time... although this require Hall sensors sets on each and every gear, making it very expensive.
It is possible to design an "intelligent" gearbox that will sense any type of failure, and warn crew about it, although I'm not sure anyone would like to pay 3 or more times more for a helicopter than one with "dumb" design.