Krzysztof Żak

Characterization of Surface Integrity Produced by Sequential Dry Hard Turning and Ball Burnishing Operations

This paper presents the state of surface integrity produced on hardened-high strength 41Cr4 steel after hard machining and finish ball burnishing. Surfaces machined by sequential machining processes were characterized using 2D and 3D surface roughness parameters. Moreover, detailed functionality of the generated surfaces was performed using a set of 3D functional roughness parameters. Among the characteristics of the surface layer, its microstructure, the distribution of microhardness and the residual stresses were determined. This investigation confirms that ball burnishing allows producing surfaces with lower surface roughness and better service properties than those generated by cubic boron nitride (CBN) finish hard turning operations.

Machinability of PF nodular cast iron with silicon nitride ceramic tools

This paper reports the experimental results for turning the pearlitic-ferritic (PF) nodular iron using silicon nitride ceramic tools. The investigations include the components of the resultant cutting force, cutting temperature, the coefficient of friction, tool wear and surface finish. In addition, surface finish is characterised based on 2D and 3D roughness parameters. Cutting tests were performed under variable cutting speed between 160 and 320 m/min, feed rate varying between 0.04 and 0.28 mm/rev and depth of cut equal to 2 mm. The data obtained and analyses can be of interest for the automotive industry.

High-Precision Machining of Hard Steel Parts Using Special Abrasive Operations

This paper presents the comprehensive approach to the determination of the geometrical and functional characteristics of surface topographies generated on hardened steel parts of about 60 HRC hardness by high-precision cutting and abrasive operations. The initial surfaces were prepared by hard turning (HT) and then finished by precision hard turning (PHT), wheel (WG) and belt (BG) grinding operations. The three surfaces were finished to obtain the Sa roughness parameter of about 0.2 μm after HT and WG operations and 0.04 μm after BG operation. Surface roughness was characterized using the standard 2D and 3D roughness parameters and the fractal and motif parameters. Some important correlations between roughness parameters and surface functional properties are revealed. This study is a part of the research project devoted to the characterization of functional surfaces produced by cutting, abrasive and burnishing operations. The results obtained in the comparative study including hard turning, belt grinding and ball burnishing operations are presented in [1].

Comparison of precision hard turning and grinding operations in terms of the topographic analysis of machined surfaces

This paper presents the comparison of precision hard cutting and abrasive processes in terms of the surface textures produced and their effects on enhancing functional properties. The main objective of such a comparison is to facilitate the decision whether to possibly replace grinding operations by hard turning with low feed rates. The experimental study performed includes hard turning operations with CBN cutting tools and grinding operations using CBN wheels. For this purpose, the stereometric features of turned and ground surfaces with the Sa roughness parameter of about 0.2 μm were compared. Apart from the set of 3D roughness parameters, the motif, fractal and frequency characteristics were analysed.