Papers by Keyword: Chemical Wear

Abstract: The machining of difficult-to-cut materials such as titanium plays a key role in several industries such as aerospace or medical. Approaches to overcome many difficulties when machining these materials can be an appropriate coating system for cemented carbide cutting tools. However, the atmosphere under which machining takes place, influencing the chemical tool wear, has not been taken into consideration. This work examines the tribochemical wear resistance of TiN, TiAlN and CrAlN coated carbide tools under different atmospheric conditions when cutting Ti6Al-4V. Air, technically pure argon and silane-doped argon is used to determine the influence of different oxygen levels on the wear behaviour of the tools. It has been found that oxidation of tools and tool coatings plays a significant role in tool wear when dry cutting titanium. Best results were generated using CrAlN and uncoated inserts where an increase in tool life up 50 % can be achieved when cutting in oxygen levels corresponding to extreme high vacuum (XHV) adequate atmospheres by using silane-doped argon. The benefits of XHV adequate atmospheres also have an effect on TiAlN-and TiN based coatings, but the chemical interaction of Ti element in the coating with the workpiece material, which presumably reduces wear resistance of cutting tools, cannot be outweighted or equalised by applying oxygen free atmospheres.

Abstract: Cemented carbides are the most common cutting tools for machining various grades of steels. In this study, wear behavior of two different cemented carbide grades with roughly the same fraction of binder phase and carbide phase but different grain size, in turning austenitic stainless steel is investigated. Wear tests were carried out against 316L stainless steel at 180 and 250 m/min cutting speeds.The worn surface of cutting tool is characterized using high resolution scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), Auger electron spectroscopy (AES) and 3D optical profiler.The wear of cemented carbide in turning stainless steel is controlled by both chemical and mechanical wear. Plastic deformation, grain fracture and chemical wear is observed on flank and rake face of the cutting insert. In the case of fine-grained, the WC grains has higher surface contact with the adhered material which promotes higher chemical reaction and degradation of WC grains, so chemical wear resistance of the composites is larger when WC grains are larger. The hardness of cemented carbide increase linearly by decreasing grain size, therefore mechanical wear resistance of the composites is larger when WC grains are smaller.

Abstract: The ceramic cutting tool requirements for metal machining are reviewed, taking into account the trends in industry towards dry high-speed cutting and the need for tools with complex geometry. The emphasis will be on bulk materials rather than on coatings and most attention will be devoted to machining of iron-based alloys (steels). In the development of new tool materials, special attention should be given to the chemical matching of tool and workpiece material at elevated temperatures. The chemical compatibility of the tool-workpiece combination can be investigated by means of static interaction couples at elevated temperatures, which have been exposed for times long enough to be able to characterise the interaction layer. Complementary to the experimental investigation, the chemical compatibility of tool and workpiece materials can be predicted from thermodynamic equilibrium solubility calculations of tool materials in a selected workpiece material. Taking into account the mechanical properties needed, new ZrO2-based composites were defined based on the thermodynamically estimated chemical stability. The selection, development and proof testing of the new ZrO2-based composites is highlighted and their wear behaviour and performance in high speed dry turning of construction steel is compared with that of state-of-the-art cutting tool materials.