Investigation of mechanical properties of hard finish turned and grinded surfaces

The main topic of the research conducted by the authors of this article is the study of the mechanical properties of surface layers after finish machining by two methods. The material of the test samples is 33NiCrMoV steel. The main aim of the authors is to compare hardness of the machined surface layers of this steel after hard finish turning and grinding. In the experimental process, quasi-static nanoindentation technique with the cube corner was used, and the microstructural analysis was performed by atomic force microscopy (AFM). Even before the start of the measurements that investigated the influence of hard finish turning technology against round grinding, it was necessary to subject the investigated 33NiCrMoV15 steel to basic research with regard to its chemical composition, fundamental microstructure and also microstructure of machined surfaces and basic mechanical and nano-mechanical properties. The microstructure was realized on the Oxford Instruments MFP-3D Infinity atomic force microscope AFM. All of these measurements were performed for investigating material properties using AF-FM viscoelastic mapping mode, which can register nanomechanical properties of materials. Chemical composition of investigated steel was performed on the spectral analyzer Spectrolab Jr CCD. Nano-mechanical properties, like nanohardness H and reduced Young modulus Er were subsequently performed on the Hysitron TI950 Triboindenter with a Cube Corner measuring tip, and then evaluated by the Triboscan software. Based on the acquired values, a 2D nanostructure of the distribution map of s H and Er was then evaluated in Matlab. This scientific research, together with all measured and calculated values, is the fundamental that will help to optimizing the quality and used all these results to optimize presented material and technological finishing processes in term of surface integrity.