Effect of the Cutting Edge Radius and its Manufacturing Procedure, on the Milling Performance of PVD Coated Cemented Carbide Inserts

The fatigue and wear behaviour of PVD coatings on cemented carbide inserts with various cutting edge radii are investigated experimentally and analytically in milling. The inserts with cutting edge radii from 8 up to 35 μm were manufactured by honing and micro-blasting. The tool wear progress was depicted through Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) microspectral analysis. The Finite Elements Method (FEM) simulation of the contact between the tool and the workpiece highlights the effect of the cutting edge radius on the first coating fracture and the further wear development. The wear behaviour of the cutting edge radii manufactured by honing, in comparison to the corresponding ones by means of micro-blasting, is significantly enhanced, whereas the cutting edge radius increasing can lead to a higher tool life.     

硬质合金涂层刀片铣削AISI410不锈钢刀具寿命研究

AISI410不锈钢广泛应用于各种工业设备的制造,如汽轮机叶片,各种泵的机械零件和蒸汽设备等。加工过程中存在着导热率低、加工硬化严重、切削力大等问题,属于典型的难加工材料。本文通过硬质合金涂层刀片铣削AISI410不锈钢正交试验,研究了硬质合金涂层刀片铣削AISI410不锈钢时刀具寿命的变化规律,归纳了相应的刀具寿命模型,并对其中的各影响因素的独立作用效果进行了分析。试验结果表明:硬质合金涂层刀片加工AISI410不锈钢时,铣削方式、每齿进给量、切削速度、轴向切削深度对刀具寿命的影响依次减小;切削速度越低,每齿进给量对于刀具寿命的影响越大;切削效率一定时,降低切削速度增大每齿进给量有利于延长刀具寿命。     

Micro-blasting of PVD Films, an Effective Way to Increase the Cutting Performance of Coated Cemented Carbide Tools

This paper investigates the feasibility of increasing the wear resistance of cemented carbide tools through micro-blasting of their PVD-coatings. The enhanced and graded film strength properties before and after micro-blasting are determined by means of a FEM-based evaluation of nanoindentation results. The coating topomorphy, induced by micro-blasting, was monitored and correlated to the substrate roughness and film adhesion. The cutting performance of inserts, coated with micro-blasted films, was investigated in milling and explained with the aid of a cutting process FEM simulation. The obtained results reveal a tool life growth through micro-blasting of coatings, deposited on substrates with appropriate roughness characteristics.     

硬质合金金刚石涂层工具基体前处理有效方法探讨

利用两种溶液浸蚀硬质合金表面，分别选择性刻蚀WC和Co.这不仅强粗化了硬质合金表面，而且，还能抑制CO在金刚石沉积过程中的负作用，从,而，提高了金刚石薄膜的质量和涂层的附着力。     

管状构件内表面真空镀膜方法研究进展

综述了国内外真空镀膜方法,包括化学气相沉积与物理气相沉积方法对管状构件内表面镀膜的研究进展,介绍了热化学气相沉积及各种等离子体(包括直流、射频及电子自旋共振等离子体)增强化学气相沉积方法在管状构件内表面镀膜方面的应用,分析了这种方法的优缺点;重点阐述了溅射镀膜方法 (包括直流二极(或三极)溅射、磁控溅射及离子束(或激光束)溅射)及电弧离子镀技术在管状构件内表面镀膜时对薄膜种类、沉积速率、薄膜厚度轴向均匀性、膜/基结合力等方面的特点。最后对管状构件内表面各种真空镀膜方法进行了分析对比,指出了存在的问题及今后的发展方向。     

Corrosion of Ni-Ti alloys in the molten (Li,K)2CO3 eutectic mixture

The corrosion of pure Ni and of binary Ni-Ti alloys containing 5, 10, and 15 wt.% Ti respectively in molten (0.62Li,0.38K)₂CO₃ at 650°C under air has been studied. The corrosion of the single-phase Ni-5Ti alloy was slower than that of pure Ni, forming an external scale composed of NiO and TiO₂. The two-phase Ni-10Ti and Ni-15Ti alloys underwent much faster corrosion than pure Ni, producing an external scale containing NiO and TiO₂, and a thick internal oxidation zone of titanium mainly involving the intermetallic compound TiNi₃ in the original alloys. The rates of growth of the external scales for the Ni-Ti alloys were reduced with the increase of their titanium content, while the internal oxidation was significantly enhanced. The corrosion mechanism of the alloys is also discussed.     

Evaluation of the propensity of replacements for halon 1301 to induce stress-corrosion cracking in alloys used in aircraft fire-suppressant storage and distribution systems

The fire-suppressant agents halon 1301 and halon 1211 have both been determined to possess sufficient ozone layer depletion potential to warrant strict limitations on their production and use. The service conditions aboard jet aircraft subject engine fire-suppressant storage vessels to the agents for long durations at elevated temperatures and pressures. Stress-corrosion cracking (SCC) of the materials of the vessel wall and/or rupture disk assembly (agent release valve) could prevent proper operation. Therefore, the compatibility of potential replacements with the materials used in the fire-suppressant storage and distribution systems is a serious concern. An evaluation of the relative SCC propensity of 12 halon replacement candidates was conducted to enable the selection of three of these compounds for further study. The slow-strain-rate (SSR) tensile test was selected, and a statistical method was developed for ranking the relative susceptibility of each alloy in each agent from the SSR test results. The results revealed that most agents had little tendency to cause SCC, but that some agent/alloy combinations were undesirable. The statistical technique allowed relative comparison, ranking, and combination of these results with other types of tests for the identification of three agents suitable for development and evaluation as aircraft fire suppressants.