Progressive tool failure in high-speed dry milling of Ti-6Al-4V alloy with coated carbide tools

This paper presents a detailed analysis of tool failure progression through an experimental study of high speed milling of Ti-6Al-4V alloy with CVD (Ti(C, N)-Al₂O₃)-coated carbide tools. The progressive tool failure characteristics under a variety of different cutting conditions were investigated. Cutting forces components and transient infrared temperature during the machining processes have been measured along with corresponding progressive tool wear when milling using coated carbide inserts under dry machining conditions. Optical microscope and scanning electron microscopic analysis results clearly show the different dominant wear regions at different stages of machining with coated carbide tools. The experimental results demonstrate that the cutting forces and the cutting temperature produced during the machining process showed an increasing trend with the tool failure progression, which in turns accelerated the tool wear progression and caused the change of the tool failure mechanisms. Furthermore, the progressive tool failure mechanisms were analyzed qualitatively. The cutting speed was correlated with progressive tool failure mechanisms, and the different conditions of friction and normal stresses caused by different cutting force and cutting temperature under different cutting speeds resulted in the varieties of progressive tool failure mechanisms.     

Cutting performance and wear mechanisms of Sialon–Si3N4 graded nano-composite ceramic cutting tools

Sialon–Si₃N₄ graded nano-composite ceramic tool materials were fabricated by using hot-pressing technique. The residual stresses in the surface layer of the graded ceramic tool materials were calculated by the indentation method. The cutting performance and wear mechanisms of the graded tools were investigated via turning of Inconel 718 alloy in comparison with common reference tools. The surface roughness of the finish hard turning of Inconel 718 and the microstructures of the chips were also examined. Worn and fractured surfaces of the cutting tools were characterized by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The results showed that graded structure in Sialon–Si₃N₄ graded ceramic tool materials can induce residual compressive stresses in the surface layer during fabrication process. Tool lifetime of graded ceramic tool was higher than that of the common reference tool. The longer tool life of the graded nano-composite ceramic tool was attributed to its synergistic strengthening and toughening mechanisms induced by the optimum graded compositional structure of the tool and the addition of nano-sized particles. Wear mechanisms identified in the machining tests involved adhesive wear and abrasive wear. The mechanisms responsible for the higher tool life were determined to be the formation of compressive residual stress in the surface layer of the graded tools, which led to an increase in the resistance to fracture.     

Experimental investigations on the failure mechanism and self-sharpening of a graded tool

To solve the urgent needs of high-performance cutting tool and high-efficient cutting process for nickel-based super alloy, a graded ceramic tool was manufactured and a series machining experiments were performed in high-speed (HS) conditions. The failure mechanisms of the graded tool were revealed by analysis the micro-structure and failure morphology. The experimental results exhibited that the primary failure mechanisms were adhesive wear, micro-chipping and flaking. For the graded tool, the step-shaped flaking surfaces and some narrow flaking strips were found on the rake face and along the cutting edge, respectively, which were the self-sharpening cutting characteristics. These characteristics should be attributed to the synergistic mechanisms of strengthening and toughening resulted from the reasonably graded structure. In addition, during the HS milling process, this characteristic was also presented on the failure faces of homogeneous tool with SiC whisker reinforced. Therefore, it is concluded that the characteristics were in a close relation to the cutting parameters and tool mechanical properties.     

The effects of cutting parameters on tool life and wear mechanisms of CBN tool in high-speed face milling of hardened steel

High-speed face milling of AISI H13 hardened steel is conducted in order to investigate the effects of cutting parameters on tool life and wear mechanisms of the cubic boron nitride (CBN) tools. Cutting speeds ranging from 400 to 1,600 m/min are selected. For each cutting speed, the metal removal rate and axial depth of cut are fixed, and different combinations of radial depth of cut and feed per tooth are adopted. The tool life, tool wear progression, and tool wear mechanisms are analyzed for different combinations of cutting parameters. It is found that for most of the selected cutting speeds, the tool life increases with radial depth cut and then decreases. For each cutting speed, the CBN tool life can be enhanced by means of adopting suitable combination of cutting parameters. When the cutting speed increases, the normal wear stage becomes shorter and the tool wear rate grows larger. Because of the variations of cutting force and tool temperature, the tool wear mechanisms change with different combinations of cutting parameters even at the same cutting speed. At relatively low cutting speed, in order to acquire high tool life of the CBN tool, the tool material should possess sufficient capability of resisting adhesion from the workpiece. When relatively high cutting speed is adopted, retention of mechanical properties to high cutting temperature and resistance to mechanical impact are crucial for the enhancement of the CBN tool life.     

Tool wear and tool life in end milling of 15–5 PH stainless steel under different cooling and lubrication conditions

Most of the machining operations on stainless steel alloys are carried out with cutting fluid due to the poor machinability of this kind of material. Tool wear mechanisms are directly influenced by the cooling and lubrication condition to which the tool is exposed, especially in interrupted cutting processes. This work investigates tool wear mechanisms for an end milling operation of a precipitation-hardened martensitic stainless steel under four different cooling and lubrication conditions. The results demonstrated that the cooling and lubrication condition strongly influences tool life and the tool wear mechanism, and furthermore, that tool lubrication rather than cooling should be the purpose for using cutting fluid in this kind of operation, in order to avoid damage caused by tool temperature variations.     

Al2O3基陶瓷刀具车削300M超高强度钢的刀具寿命研究

采用对角正交回归试验法,求得Al2O3基陶瓷刀具切削300M超高强度钢的刀具寿命经验公式,并分析了切削用量对刀具寿命的影响.通过扫描电子显微镜的观察和能谱分析仪的分析,对Al2O3基陶瓷刀具的损坏形态和磨损机理进行了研究.研究表明:Al2O3基陶瓷刀具车削300M超高强度钢时,粘结磨损和磨粒磨损是主要的磨损机理;合理的切削参数为:切削速度200～300 m/min、切削深度0.1～0.15 mm、进给量0.05～0.1 mm/r.     

稀土增韧补强Al2O3/(W，Ti)C复相陶瓷刀具材料的研究

研制出一种稀土补强Al     

Simulation of machining 3D free-form surface in normal direction using 6-SSP and 4SPS+UPU parallel machine tools

A novel 6-SSP parallel machine tool and a novel 4SPS+UPU parallel machine tool are presented, and a novel CAD approach is proposed to machine a 3D free-form surface in its normal direction by using the two parallel machine tools. First, by adopting the CAD geometry constraint and dimension-driving technique, the simulation mechanisms of a 6-SSP parallel manipulator with 6-DOF and a 4SPS+UPU parallel manipulator with 5-DOF are created. Second, a 3D free-form surface and a guiding plane of tool path are constructed above the moving platform of the two simulation mechanisms. Third, the tool axis of simulation parallel machine tool is retained perpendicular to the 3D free-form surface. In the light of two prescribed tool paths, the driving limbs and the pose of the moving platform of parallel machine tools are solved automatically and visualized dynamically.     

Performance assessment of microwave treated WC insert while turning AISI 1040 steel

This study attributed to post treatment of tungsten carbide (WC) inserts using microwave irradiation. Tungsten carbide inserts were subjected to microwave radiation (2.45 GHz) to enhance its performance in terms of reduction in tool wear rate, cutting force surface roughness and improvement in tool life. Performance of tungsten carbide insert is very much affected by machine operating parameters i.e. speed, feed and depth of cut. An attempt has been made to investigate the effects of machining parameters on microwave treated tool inserts. This paper describes the comparative study of machining performance of untreated and microwave treated WC tool inserts used for turning of AISI 1040 steel. Machining performance has been evaluated in terms of flank wear, cutting force, surface roughness, tool wear mechanisms. Critical examinations of tool wear mechanisms and improvements in metallurgical properties such as microstructural change, phase activation of WC grains were identified using scanning electron microscope (SEM). Results obtained from the turning using the microwave treated tool inserts showed a significant reduction tool wear thereby enhancing the surface quality of workpiece.     

花岗石异型面高效加工刀具磨损破损研究

基于实验和观察,从宏观和微观两方面研究了高效加工花岗石异型面时刀具磨损破损的形态和机理,基于研究结果,提出异型石材加工刀具的改进设计方案。     

自增韧陶瓷的增韧机理研究

对陶瓷的增韧补强机理进行了探讨，分析了自增韧陶瓷的自增韧机制及影响因素。通过控制烧结过程，使一部分氮化硅晶粒发育成具有较大长径比的β—Si3N4柱状晶，从而获得类似于晶须增韧复合材料的增韧机制，以提高氮化硅陶瓷刀具的断裂韧性和抗弯强度。     

钛合金切削加工中刀具寿命和刀具磨损的研究

钛合金是典型的难加工材料,提高钛合金的加工效率和刀具寿命是急需解决的问题。本文选用Ti-6Al-4V作为工件材料,选取两种不同的硬质合金和一种聚晶金刚石(PCD)作为刀具材料,对切削加工中刀具寿命和刀具磨损进行了试验研究。研究结果表明:PCD刀具寿命明显高于硬质合金刀具,在高速下优势尤其明显;两种硬质合金刀具低速下主要是粘结磨损,高速下主要是粘结磨损、扩散磨损和氧化磨损;PCD刀具主要是微崩刃和石墨化引起的沟槽磨损。     

Reproducing wear mechanisms in gear hobbing—Evaluation of a single insert milling test

Gear hobbing is a widely used method in industrial gear manufacturing. The most common type of hob is made of homogenous HSS and protected by a PVD coating. In order to increase the reliability and tool life of these milling tools, further developments of the tool surfaces and cutting edges are necessary.A single tooth milling test, using a HSS insert in a conventional milling machine, has been developed with the aim to reproduce the wear mechanisms seen on real HSS gear hobbing teeth. The benefits of such a test, compared to actual gear hobbing tests, are primarily accessibility and reduced costs for both design and production of test specimens (inserts).The main goal of this study was to verify that the wear mechanisms in the developed test correspond with the wear mechanisms obtained in real gear hobbing. Once this was verified, the influence of surfaces roughness on the performance of TiAlN coated HSS inserts was evaluated by using the tool as delivered or after polishing the tool surfaces. Parameters considered were tool wear, cutting forces and the quality of machined surfaces. The polished inserts, yielded less adhered work material and reduced flank wear but no significant difference in cutting forces as compared to the unpolished inserts.     

车削司太立合金时硬质合金刀具失效机理的试验研究

通过切削试验,研究了YG610和YS8两种硬质合金刀具车削难加工材料司太立合金的刀具失效机理。结果表明:YG610刀具的硬度和韧性都相对较好,刀具失效形式表现为磨损;YS8刀具硬度高,但韧性略有不足,刀具失效形式主要为破损。     

An investigation on wear mechanism of high-speed turning of free-cutting steel AISI 1215 using uncoated and multi-layer coated tools

AISI 1215 is a new kind of green and non-toxic free-cutting steel with minimum environmental pollution and excellent machinability, which receives wide promotion, investigation, and application in manufacturing industries. In machining of AISI 1215 steel, tool wear has a close relation with the presence of manganese sulfide lubricant zone formed on the tool surface. In this work, with the aid of cutting temperature and tool Von Mises stress simulations, tool wear analysis on the uncoated and multi-layer (Al₂O₃/TiCN) coated carbide tools was performed in high-speed turning operation. Wear pattern and wear mechanisms were studied through the experimental results. The main findings showed that the uncoated tool suffered high cutting temperature and severe tool wear and was not conducive to form a manganese sulfide lubricant zone in the turning operation. In contrast, the multi-layer coated tool could form a manganese sulfide lubricant zone on the chip–tool contact area. The beneficial roles of the manganese sulfide lubricant zone formed on the coated tool surface can be summarized as lubrication and diffusion blocking. The main wear mechanisms of the uncoated tool were crater wear, oxidation wear, adhesive wear, and abrasive wear, whereas for the multi-layer coated tool, they were crater wear, adhesive wear, and abrasive wear.     

用作平面虚拟轴机床的三自由度平面并联机构的型与运动分析

研究了能用作平面虚拟轴机床的三自由度平面并联机构的可能的类型。分析了其中典型机构的逆解的求解及其相应刀具中心的轨迹     

刀具磨损过程中的切削力特征研究

在相同的工件材料、刀具材料、切削参数和不同的刀具磨损状态下,从时域角度分析了刀具磨损状态对三向稳态切削力的影响,从频域角度利用FFT分析、功率谱分析等工具研究刀具磨损状态对动态切削力的影响情况,并对影响的机理进行讨论。分析结果表明刀具磨损状态迫使受动态力的刀具弯曲振动频率幅值和局部频率能量增大。     

细晶粒硬质合金刀具铣削钛合金损坏机理的研究

基于用Y330细晶粒硬质合金刀具高速铣削Ti6Al4V钛合金的试验,分析了刀具的损坏形态和失效机理。结果表明,在给定的切削条件下,刀具的损坏形态以崩刃和灼烧为主,同时伴有表面材料扩散。据此提出了延长刀具寿命、提高加工效率的途径。     

Wear mechanisms analysis for turning Ti-6Al-4V—towards the development of suitable tool coatings

Titanium alloys are materials of choice for a wide range of applications. Their high strength and low density make them suitable for aerospace applications. Titanium-based alloys also exhibit excellent corrosion resistance and are bio-compatible, making them suitable for prosthetic applications like orthopedic transplants. The reactivity as well as heat resistance of titanium-based alloys, however, renders them difficult to machine. Based on previous research involving the development of a wear map for Ti-6Al-4V alloy, this research aims to identify the wear mechanisms associated with tool deterioration across different regions of the wear map. The characterization of wear mechanisms with respect to machining conditions and tool wear rate would ultimately help in the development of suitable tool coatings for machining titanium-based alloys.     

新型6-SPS并联机床局部承载能力分析

应用并联机器人机构学理论 ,定义了一种新型 6 SPS并联机床处于初始装配位姿时的承载能力性能指标 ,并分析其承载能力性能指标与结构参数关系 ,为设计和使用该结构方案的并联机床提供理论依据。