Quantitative Microstructural Analysis of Nanocrystalline Surface Layer Induced by a Modified Cutting Process

Volker Schulze; Frederik Zanger; Florian Ambrosy

doi:10.4028/www.scientific.net/AMR.769.109

Paper Titles

Waterjet Turning of Titanium Alloys
p.77

A New Method for the Preparation of Cutting Edges via Grinding
p.85

Hot Machining: Utilisation of the Forging Heat for Efficient Turning at Elevated Temperatures
p.93

Numerical Investigations on Cutting of Dual-Phase Sheet Steel with an Emphasis on Material Damage at the Cut Edge
p.101

Quantitative Microstructural Analysis of Nanocrystalline Surface Layer Induced by a Modified Cutting Process
p.109

Cutting of Nickel-Based Superalloys with Rotating Indexable Inserts
p.116

Polishing Process of Ceramic Tiles - Variation of Contact Pressure
p.124

Low Frequency Vibration Assisted Drilling of Aluminium Alloys
p.131

Analytical Modelling of Temperature Distribution Using Potential Theory by Reference to Broaching of Nickel-Based Alloys
p.139

HomeAdvanced Materials ResearchAdvanced Materials Research Vol. 769Quantitative Microstructural Analysis of...

Quantitative Microstructural Analysis of Nanocrystalline Surface Layer Induced by a Modified Cutting Process

Abstract:

Present work analyzes the influence of process and modified geometry parameters of an orthogonal final machining process (finishing) on the nanocrystalline surface layers generation by quantitative microstructural analysis. Thereby, AISI 4140 (German Steel 42CrMo4) in a state quenched and tempered at 450°C is used as workpiece material. Metallic materials used in technical applications are polycrystalline in nature and are composed of a large number of grains which are separated by grain boundaries. The grain size has a strong influence on the mechanical material properties. Metallic parts with a severe nanocrystalline grain refinement in the near-surface area show many beneficial properties. Such surface layers considerably influence the friction and wear characteristics of the workpiece in a subsequent usage as design elements working under tribological loads due to their extreme superplastic properties. The tribologically induced surface layers formation already starts during the manufacturing of the components, by leading to a change of workpiece material near the surface. Particularly when the depth of cut h becomes of the same order as the cutting edge radius r_ß, the ploughing process becomes increasingly important and strongly influences the chip formation process. The plastic zone depth within the surface layer is especially influenced by the design of the microgeometry of the cutting tools and increases almost linearly with the ratio of cutting edge radius r_ß to depth of cut h. The plastic zone is hereby approximately of the same order of magnitude as the cutting edge radius r_ß. Parameters that are studied and taken into account in the manufacturing process are cutting edge radius r_ß, depth of cut h and cutting velocity v_c. Variations of cutting depth h are performed in a range of 30 to 100 µm and variations of cutting edge radius r_ß are executed in a range of 30 to 150 µm. The microgeometries of the tools are preconditioned by abrasive grinding with a drag finishing machine and observed by a confocal light microscope. A cutting velocity v_c of 25 and 150 m/min is applied. The evaluation of the manufacturing process is carried out by detailed analyses of the microstructural conditions in the surface layer after processing using a Focused Ion Beam system. These material characterizations provide information about the surface engineering concerning the microstructural changes in the workpiece surface layer due to machining. Hereby, the grain size analysis is investigated by a line method based on the characterization of portions of several test-lines positioned across the two dimensional Focused Ion Beam images.