To study the influence of voltage levels on ion nitriding effect a new controller to have a specified constant nitriding temperature has been designed by the method of pulse width modulation. This controller can also keep a stable glow discharge by preventing are formations, that makes it possible to have relatively high voltage levels and low temperatures.
To compare the nitriding effect under different conditions, a quantity is defined based on hardness distributions, such that,
Quantity of Nitriding effect = αㆍ∫ΔHㆍdV,
Where α is a dimensionless proportional constant depending on materials, and ΔH denotes the increase of hardness over core hardness. This quantity has the dimension of energy and when divided by the input electric energy, a dimensionless relative efficiency of nitriding effect is obtained.
Two voltage levels, 500V and 800V, were tested under various nitriding temperature and times, with SCM 4. The surface hardness and the case depth obtained by 800 V were significantly larger than those by 500 V, under the same temperature and time condition, but the latter case consumed less energy than the former. The relative efficiency for 800 V, however, was not less than that for 500 V. A specified quantity of nitriding effect can be obtained in reduced time when a higher voltage level is used.
