A study on surface roughness of ion machining.

This paper presents the influence of the machining conditions : the machining time, the ion (argon) energy, the ion current density and the beam angle on the surface roughness and on the machining depth for the high chromium-high carbon steel (SKD 1). Also, the characteristic of roughness is discussed from the measurement of the surface asperities by a scanning electron microscopy and the analysis of chromium by an electron probe micro analysis. In addition, as the method to obtain a good surface roughness, Floating Method which applies the positive charge to the workpiece is tested. The results obtained are as follows : (1) The machining depth increases linearly with the time, but the surface roughness is not changed significantly at the initial stage of the machining (up to about 0.03 μm depth) and at the subsequent stage the surface roughness increases with the time. (2) The smaller the ion energy and ion current density, the lower the surface roughness becomes. And as the ion current density decreases, the surface roughness becomes independent from the ion energy. (3) Although the maximum machining depth is found at about 50 degress of the beam angle, the minimum surface roughness is found at about 70 degrees. (4) By Floating Method, the size of the workpiece can be controlled with a high level of accuracy without a change of the surface roughness. (5) The surface roughness of cromium-carbide in SKD 1 decreases only slightly.