- 上一篇：探索Activity的生命周期英文文献和中文翻译
- 下一篇：疏磨机设计英文文献和中文翻译
Insert set 2 gave the best performance in the wear tests (Table 2). In the X-ray diffraction analysis, it is found that W2B compound is dominating in the structure of insert set 2. The wear resistance is closely related to existence of W2B compound due to
104 S. Basturk et al. / CIRP Annals - Manufacturing Technology 59 (2010) 101–104
Fig. 5. SEM images of inserts after wear tests (images are taken at the test termination times for one set of wear tests).
Fig. 6. Evolution of VB of nonboronized and plasma boronized WC inserts (wear tests were terminated when VB values reach 300 mm)
tungsten boride’s high hardness and chemical inertness. In the other insert sets, domination of W2B5 is observed in the XRD analysis in parallel to the wear test results given in Table 2. W2B5
formation is due to the increase in the amount of boron that diffuses into the inserts and due to the change in chemical reaction kinetics at different temperatures and plasma boronizing dura-tions. Therefore, reactor temperature and plasma durations are clearly very important to control wear resistance of plasma boronized WC tools.
Titanium has the following characteristics cutting
(1) deformation coefficient is small: This is a distinctive feature of titanium alloy machining, deformation coefficient is less than or close to one. Chip knife from the front surface of the sliding friction increases greatly accelerated tool wear.
(2) Cutting temperature is high: Because the thermal conductivity of titanium is very small (only about 1/5 to 1/7 45 steel), chip and rake face contact length is extremely short, the heat generated when cutting difficult to pass a focus on a smaller range of the cutting area and near the cutting edge, high cutting temperatures. Under the same cutting conditions, cutting temperature than 45 steel cutting more than double.
Cutting force (3) on the basis of large: the main cutting force of about 20% smaller than when cutting steel, since the chip and rake face contact length is extremely short, the contact area on the unit cutting force greatly increased, likely to cause chipping. At the same time, because of the small elastic modulus of the titanium alloy, the processing in the radial force prone to bending deformation caused by vibration, increased tool wear and impact the accuracy of parts. Therefore, the required process system should have better rigidity.
(4) Chilled serious: Because the chemical activity of titanium is large at high cutting temperatures, it is easy to absorb nitrogen and oxygen in the air to form a hard and brittle crust; while the cutting process can also cause plastic deformation of surface hardening . Chilled phenomenon will not only reduce the fatigue strength of parts, but also to increased tool wear is a very important feature when cutting titanium.
(5) Tool wear: blank after stamping, forging, machining methods such as hot-rolled to form a hard and brittle uneven skin, can easily result in chipping, making the removal of titanium alloy crusty become the most difficult step. In addition, because the tool material titanium strong chemical affinity, on the cutting unit area under high temperature and cutting power conditions, the tool is easy to produce adhesive wear. Turning titanium, sometimes rake face even more serious than the wear flank; feed rate f <at 0.1 mm / r, wear occurs mainly in the rear flank face; when f> at 0.2 mm / r, front flank wear will occur; carbide tool finishing and semi-intensive car, flank wear to VBmax <0.4 mm more appropriate.
4. Summary
For the first time in the literature, a novel plasma boronizing process was implemented on WC tools and its effects were investigated on cutting forces and on tool life. SEM images showed that plasma boronizing process caused the generation of the boron penetrated zone on the rake and clearance surfaces of tool. When the temperature and duration of plasma reaction are selected properly, microhardness and depth of boron penetration zone can be increased to have high wear resistances. Orthogonal and oblique machining tests were performed on Ti–6Al–4V to compare performances of the nonboronized and plasma boronized tools. It was observed that plasma boronized tools help to lower the cutting forces slightly. More importantly, plasma boronizing process increases tool cost less than 5%, while it helps to increase the WC tool life triple. The new plasma boronizing of WC tools is found as a promising method and has significant potentials for being cost effective solutions for titanium machining.