PLASMA NITRIDING: POPULAR BELIEFS UNMASKED
TEST PHASES
To summarise the tests performed, it is possible to say that we have defined three representative classes, identified as PLASMA 1, PLASMA 2 and PLASMA 3: in each of these configurations only one of the parameters characterising the plasma has been changed to finally identify the ideal combination.
The method suggested by the manufacturers (i.e. standard parameters, identified as PLASMA 1) immediately revealed the inadequacy of the treatment for products with holes, having generated the hollow cathode with consequent localised melting of the steel near the hole inlet, as shown in the images below:
Fig. 1: melting at the hole inlets due to the hollow cathode phenomenon
To monitor the phenomenon, further tests were subsequently carried out, carefully positioning the process control thermocouple near a hole or creating an ad hoc simulacrum and varying the plasma parameters (PLASMA 2):
Fig. 2: Charging example with thermocouple localisation in a simulacrum
