Use of Integral Characteristics in the Evaluation of Surface Texture of Components after Plasma Nitriding

The paper presents the use of integral methods of surface texture evaluation of structural steel samples used in armaments production for the analysis of the functional behaviour of gear surfaces. The aim of the paper is to evaluate the relationship between the quality of the ground surface and the surface after the plasma nitriding process and the functional properties of the surface using unconventional characteristics. These characteristics include Amplitude Distribution and Material Ratio, Autocorrelation Function (ACF), Frequency Spectrum (FS) and Power Spectral Density (PSD). These characteristics can, for example, reveal small changes in surface texture caused by both the cutting tool and surface treatments, such as diffusion nitriding technology, which show only slight changes in standard parameters. Thus, these characteristics can be used as a suitable diagnostic tool for evaluating changes in the functional properties of surfaces. These changes can usually be characterized by wavelength profile inequalities and statistical and spectral properties. In this paper, the surfaces of C45, 15NiCr13, 18CrNiMo7-6 and 16MnCr5 steels after the finishing operation of grinding and further after plasma nitriding are evaluated. Measurement of the standard parameter, i.e. the arithmetic mean height Ra , of ground and nitrided surfaces resulted in the same or slightly higher values after diffusion technology. Using integral characteristics, changes in surface texture were found to be directly related to the functional behaviour of surfaces in interaction and can predict, for example, noise levels, wear and lubrication properties.