On tool life, usually depending on the workpiece and tool materials, and different cutting processes. One way of quantitative analysis tool life termination point is to set a maximum acceptable flank wear limit (expressed in VB or VBmax). Expected tool life available tool life of Taylor formula, namely VcTn = C, One such formula is the more common form of VcTn × Dxfy = C formula, Vc cutting speed; T is the tool life; D is the cutting depth; f the feed rate; x and y are determined by experiment; n and C are based on experimental or technical information has been published to determine the constants that represent the tool material, workpiece and feed rate characteristics.
Best evolving tool substrate, coating and cutting edge preparation techniques for limiting cutting tool wear and resistance to high temperatures is essential. These elements, together with chip-breaker and on the corner arc radius indexable inserts used to determine the applicability of each tool for different workpiece and cutting. All the best combination of those elements can extend tool life, so cutting more economical and reliable.
By changing the tungsten carbide particle size in the range 1-5μm, tool manufacturers can change the properties of the matrix carbide cutting tools. Particle size of the base material for cutting tool life and plays an important role. The smaller the particle size, the better the wear resistance of the tool. Conversely, the larger the particle size, the better the strength and toughness of the tool. Fine particulate matrix is mainly used for machining aerospace grade materials (such as titanium, Inconel alloys and other high-temperature alloys) blade.
In addition, the tool material carbide cobalt content of 6% -12%, you can get a better toughness. Thus, the cobalt content can be adjusted to meet the requirements of a particular machining, regardless of its wear resistance or toughness requirements.
Performance tool substrate can also selectively carbide material to add other alloying elements (such as titanium, tantalum, vanadium, niobium, etc.) to obtain enhanced by the rich layer is formed close to the outer surface, either. Rich layer can significantly improve the strength of the cutting edge, thereby improving performance roughing and interrupted cutting tool.
In addition, the choice of materials and processing methods and the workpiece to match the tool base, but also consider the performance of five additional matrix properties - fracture toughness, transverse rupture strength, compressive strength, hardness and thermal shock resistance. For example, if the carbide cutting tools appear along the cutting edge chipping phenomenon, it should be used with a high fracture toughness of the matrix material. In the case of the tool cutting edge direct failure occurs or damaged, it may use solution is used with a high transverse rupture strength or higher compressive strength of the base material. For higher cutting temperature processing situations (such as dry cutting) should normally be the first choice of high hardness tool material. The tool can be observed in the thermal cracking of processing situations (most common in milling), it suggested the use of good thermal shock resistance of the tool material.
Coatings also help to improve cutting performance. Current coating technologies include:
① titanium nitride (TiN) coating: This is a common type of PVD and CVD coating, can increase the hardness and oxidation temperature of the tool.
② titanium carbonitride (TiCN) Coating: By adding carbon in the TiN, increases the hardness and surface finish coating.
③ titanium aluminum nitride (TiAlN) and nitrogen titanium aluminum (AlTiN) coating: Alumina (Al2O3) layer and the application of these coatings can improve the high temperature composite cutting tool life. The alumina coating is particularly suitable for dry cutting and cutting nearly dry. AlTiN coated aluminum content is higher, the higher the titanium content compared TiAlN coating, has a higher surface hardness. AlTiN coatings are typically used for high-speed machining.
④ chromium nitride (CrN) coating: This coating has good anti-blocking properties, is against BUE preferred solution.
⑤ diamond coating: diamond coating can significantly improve the processing of non-ferrous group material cutting tools, is very suitable for machining graphite, metal matrix composites, high-silicon aluminum and other highly abrasive materials. However, diamond coating is not suitable for machining steel, because a chemical reaction with the steel will destroy the adhesive properties of the coating and the substrate.
In recent years, the market share of PVD coated tools has expanded, its price is comparable with CVD coated tools. CVD coating typically has a thickness of 5-15μm, and the PVD coating has a thickness of about 2-6μm. Applied to the tool in the basic body, CVD coating will produce undesirable tensile stress; and PVD coating helps the matrix formed beneficial compressive stress. Thicker CVD coatings are usually significantly reduce the strength of the cutting edge. Therefore, CVD coating can not be used to require a very sharp cutting edge of the tool.
In many cases, the preparation of the blade cutting edge (or edge passivation) has become a watershed in the success of the decision process. Passivation process parameters to be based on the specific processing requirements. For example, for high-speed finishing steel blade on edge passivation seeks differ for roughing blades. Edge passivation process can be applied to almost any type of carbon steel or alloy steel blade, and the blade machining stainless steel and special alloy materials, there are certain restrictions apply. Deactivating amount can be as small as 0.007mm, as large as 0.05mm. In order to play to enhance the cutting edge in the harsh conditions of processing, it can also be formed with a small T-shaped edge by edge passivation.
In general, for most continuous turning and milling steel and cast iron blade edge needs to be a greater degree of passivation. Passivation depends on the type of carbide grade and coating (CVD coating or PCD). For heavy interrupted cutting blade on the edge of the passivation or re-processing of the T-shaped rib belt has become a prerequisite. Depending on the type of coating, the amount of passivating accessible 0.05mm.
In contrast, since the processing of stainless steel blade and high-temperature alloys BUE easily formed, thus requiring sharp cutting blade holder, only slight passivation (as small as 0.01mm), you can even customize a smaller amount of passivation. Similarly, aluminum processing blade is also required to have a sharp cutting edge.