© Copyright by International OCSCO World Press. All rights reserved. 2006 VOLUME 18 ISSUE 1-2 September–October 2006 of Achievements in Materials and Manufacturing Engineering of Achievements in Materials and Manufacturing Engineering Short paper 367 1. Introduction Hard turning (HT) of steel workpieces harder than 60 HRC with mixed ceramic and PCBN cutting tools can be essentially performed as rough, precision, and high precision operation when the Rz parameter is less than 1 Pm [1,2]. Precision finishing of hardened steel components using superhard cutting tools offers manufacturers an attractive alternative to traditional grinding. In particular, it can often cut manufacturing costs, decrease production time, and improve overall product quality [1-4]. According to many industry reports, hard machining (HM), sometimes termed as hard part machining (HPM), covers both turning and milling, generally semi-finishing and finishing, operations. Gears and axles, and bearing components are typically Surface integrity of hardened steel parts in hybrid machining operations W. Grzesik a, *, J. Rech b , T. Wanat a a Department of Manufacturing Engineering and Production Automation, Technical University, Opole, Poland b Laboratory of Tribology and Systems Dynamics, ENISE, Saint-Etienne, France * Corresponding author: E-mail address: grzesik@po.opole.pl Received 15.03.2006; accepted in revised form 30.04.2006 Manufacturing and processing AbstrAct Purpose: Purpose of this paper is the investigation of surface integrity generated in hard turning and subsequent finish abrasive machining. The primary reason for undertaking this problem was insufficient magnitude of compressive residual stresses after hard turning which determines the fatigue resistance of highly loaded transmission parts. Design/methodology/approach: Methodology employed uses 2D and 3D description of the surface roughness/ surface microstreometry and the X-ray diffraction method for measurements of residual stresses. The main scope of this research program is to record the relevant changes of surface layer features resulting from the application of finish abrasive passes. Findings: Findings can be distinguished into two groups. First, finish belt grinding produces the residual stresses with the maximum value of–1000 MPa, which is satisfactory for improving fatigue life. Second, the bearing properties improve due to displaying negative values of the skew. Research limitations/implications: Research limitations deal with the identification range of 3D roughness parameters and the lack of modern equipment for robust measurements of residual stresses: Future research should be focused on the stronger correlation between technological and exploitation properties of the surfaces produced by hard and abrasive technologies. However, it needs more detailed inputs from automotive industry. Practical implications: Practical implications are related to the automotive industry, especially to manufactures of such transmission elements as synchronizing cones/planes on gear wheels. The sequences of new hybrid machining processes are partly verified in terms of industry needs (machining conditions, machine tools, special equipment, cutting and abrasive tools). Originality/value: Originality of this industry–oriented contribution is based on the aggregating hard cutting and abrasive machining processes. The practical value of the paper is that it proposes a very beneficial machining process for highly loaded hardened parts. Keywords: Machining; Hybrid process; Surface roughness; Residual stress 1. Introduction