Key Engineering Materials Vols. 589-590

Abstract: Ti(C,N)-TiB₂-WC composite ceramic cutting tool materials with nano-scale additives Ni and Mo, and micro-scale additives Ni and Mo as sintering aids were sintered respectively at a temperature of 1550 °C for holding time of 1hour in vacuum by a hot-press technique. The effects of nano-scale additives Ni and Mo, and micro-scale additives Ni and Mo on microstructure and mechanical properties of composites were compared and investigated. It is concluded that the wettability of nano-scale Ni and Mo to the composites is better than that of micro-scale Ni and Mo. The nano-scale whiskers were found in the composite ceramic tool materials with nano-scale additives. The addition of nano-scale Ni and Mo instead of micro-scale Ni and Mo could make the flexural strength and fracture toughness of Ti(C, N)-TiB₂ –WC composites have a promotion, but could not make the hardness of the composites increase in this study.

Abstract: Talyor formula is widely accepted to describe tool wear and is employed to optimize cutting parameters. The common test methods and processes of cutting tool wear test are firstly investigated in this paper. The effects of interference factors on different test methods are analyzed by hypothesis test to find the reason that regression generalized Taylor formula is partly invalid or not effective. The meaning of exponentials in generalized Taylor formula is discussed and tool wear test principle for difficult-to-machine materials is proposed at last.

Abstract: A purely analytical method, based on the meshing theory, is presented to establish the exact helical groove and circumferential cutting edge model of end mills, for the solution of its low design precision and efficiency problems. Firstly, a coordinate system to represent the relative space position relations between grinding wheels and end mills is built and the mathematical model of the helical groove is precisely calculated with a given wheel profile and relative movements between the wheel and the workpiece. Then, the rake angle, inner radius and wheel positions of machining the clearance faces is computed. Finally, a 3D model of the end mill is generated by using OpenGL.

Abstract: This paper analyzes the reasons of the defects generation of the ceramic cutting tool materials. The defects in the ceramic cutting tool materials are caused by chemical compatibility and physical mismatch during the designing process, and caused by grain abnormal growth and sintering parameters during the preparation stage. The database of low defect ceramic cutting tool is established and the data structure of the database is described. The users can use the database to design the tool material system through the mode that can reduce the defects.

Abstract: Ti2AlNb-based alloy is regarded as lightweight high-temperature structural material, which is expected to replace the nickel-base super alloy due to its low density, high elastic modulus, strength retention at elevated temperature, outstanding oxide resistance. However, these excellent properties also make Ti2AlNb to be difficult-to-cut material. In this paper, the milling experiment of Ti2AlNb alloy was carried out using Ti(N,C)-Al2O3 coated cemented carbide tools. SEM and EDS analysis was utilized to observe the worn tools to determine the tool failure modes and wear mechanisms. Tool life when milling Ti2AlNb was short and heavily dependent on the cutting parameters. During milling, coating material of the tool was separated rapidly from the base material. When the cutting speed exceeded 100m/min, serious cracks appeared on the tool surface. Thermal fatigue, adhesive and attrition were the predominant wear mechanisms of the coated tools.

Abstract: Reasonable tool condition has crucial importance to prevent tool malfunction such as abnormal wear, chipping and cutting teech breakage when broaching expensive components i.e. gas turbine engines disks. This paper proposes a broaching simulation test method of using customized single tooth groove tools with a variety of rake angle and clearance angle to simulate broaching processing at shaper machine under different cutting depth. The effects of tool condition and cutting depth on cutting forces, surface roughness analyzed by Response Surface Methodology and surface morphology of machined surface were discussed, which revealed that the changes of cutting depth play a dominate role in processing quality, followed by tool rake angle, and tool clearance is subordinate. Good tool edge strength should be assured from prevent shock and vibration during the selection of tool condition.

Abstract: In this paper, considering material properties and processing characteristics of titanium alloys, the milling tool under the machining condition of large cutting depth and quasi-high speed is designed, and the face milling cutter with integral CBN inserts is developed. Then, the solid model of the CBN face-milling cutter is built by the three-dimensional modeling software Pro/E. At the same time, based on the platform of finite element simulation analysis, the deformation and stress analysis of the overall structures are carried out. It turns out that: the maximum stress of the cutter blades is not in the cutter tip region but distributed approximately along the direction of the main cutting edge, the maximum stress of the tool body is at the bottom of the groove for insert. The maximum stress acting on the wedge is at the bottom of the contact area between the wedge and the cutter body. Strength sensitive area of the clamping screw happens in the connection root. Through the static analysis, the reasonableness of structural design of the tool is evaluated theoretically.

Abstract: Micro turn-milling has superiority on the productivity and the quality of work pieces, and is more suitable to machine micro-shaft parts and desirable miniature parts based on the turn-milling technology. On the basis of ADAMS and UG software, kinematics simulation of complete machine has been performed, meanwhile, the natural frequency and vibration mode of micro turn-milling machine tool has been analyzed by adoption of modal analysis in this paper. The results forecasts dynamic characteristics of micro turn-milling machine tool. It also provides important reference frame of dynamic optimization design of micro turn-milling machine tool.

Abstract: In the paper, the crack parallel to and lying on the interface in the hard cladding material structure is regarded as the research object, theoretical model of the stress intensity factor (SIF) of the interface crack under the mechanical impact load is built. Based on it, the SIF of the crack parallel to and lying on the interface in the cermet cladding material structure under the mechanical impact load is investigated by using finite element analysis method. The influences of the cladding thickness ratio and mechanical impact stress amplitude on the interface SIF are investigated. The research results show that, at a certain moment, the interface SIFs decrease with increasing cladding thickness ratio when the mechanical impact stress amplitude is a constant and increase as the mechanical impact stress amplitude increases when the cladding thickness ratio is a constant.

Abstract: Through the experiment of cutting 45 steel, the influence of boronizing on Ti (C,N)-based ceramic cutting performance in different cutting speeds were discussed. The test results indicated that: regardless of boriding, cutting speed has a great influence on the life of Ti (C,N)-based ceramic cutting tool. Within the limit of 200~400 m/min, the lower the cutting speed is, the longer tools life. At the minimum speed, boronizing greatly improves cutting performance and doubles tool life. It has no significant but negative effects once over 300 m/min. The decrease of the abrasion resistance of boronized layer is mainly influenced by the intense thermal shock of high speed cutting.