Surface topography analysis of precision assemblies of fuel injector nozzles

Precision surface assemblies can be found in the two locations in a fuel system of a diesel engine. These parts are the pumping section in an injection pump and the injector nozzles. In this paper the authors present the results of surface topography measurements of precise surface assemblies of some fuel injectors. The measurements have been made with the atomic force microscope (AFM) NT-206. The results of surface topography measurements were presented in the form of 2D and 3D images and also as surface roughness profiles in some selected cross-sections of the investigated surfaces. It has been also shown cumulative roughness height distribution and roughness height distribution as well as Minkowski volume (first Minkowski functional). After scanning the surface on the atomic force microscope, the obtained data were processed with the SurfaceXplorer ® 1.311 and Gwyddion 2.35 software. The study concerned some new injector nozzles and also injector nozzles after a certain time of operation. The side and the conical precise surface assembly of the injector nozzle body and needle were tested. The atomic force microscope NT-206 allows to perform a surface scan of the sample with maximum dimensions of 32x32 μm and a maximum height of roughness ± 1 μm. Scanned area was divided into 256x256 measurement points, while the measurement was carried out in a static (contact) mode. The results presented in this paper also includes the calculated values of Ra, Sa (roughness average) and Rq, Sq (root mean square roughness) surface roughness parameters and the value of the skewness Ssk (Rsk), kurtosis Sku (Rku) and maximum distance between the lowest valley and the highest peak of investigated surface – Rt. The obtained data allow evaluating the degree and type of wear of tested surfaces on the micro-scale