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(1) Development concept of a new generation of coated blades
In the past development of tool materials, if the wear resistance of the material is improved, the anti-cracking performance will be weakened; on the contrary, if the anti-crushing performance of the material is improved, the wear resistance will be impaired, and it is difficult to achieve both advantages. Effect. Sandvik's philosophy of developing new tooling materials is to improve both its wear resistance and chipping resistance, making it an excellent match and achieving the best overall performance. The company's recently developed new coated inserts are a good example of this concept. The following highlights the black gold CVD coating and the bronze multi-layer PVD coating.
(2) Characteristics of black gold CVD coating
The newly developed black gold CVD coating is a coating material with excellent wear resistance and chipping resistance. Ordinary CVD coatings have a coating temperature of more than 1000 ° C. Due to the difference in thermal expansion coefficient between the coating and the cemented carbide substrate, tensile residual stress is generated in the coating, which tends to cause coating peeling and hot cracking during cutting. The main factor of cutting performance. In addition, the ordinary coating is composed of a brittle material, and when the thickness of the coating is increased, the coating is also prone to peeling off, that is, if the heat resistance and wear resistance of the coating are prioritized, the peeling resistance is sacrificed.
Unlike conventional coatings, the newly developed black gold CVD coating combines two properties, namely a thicker coating and excellent flaking resistance. Its main feature is that it adopts special surface treatment technology developed independently to greatly reduce the residual tensile stress in the coating, so that the thickened coating has good anti-flaking property while improving wear resistance, which not only improves The wear resistance required for continuous cutting increases the chipping resistance and chipping resistance required for interrupted cutting.
(3) Processing properties of black gold CVD coating
The following is an example of two machining examples of a GC4525 blade turning steel that has been treated with a black gold CVD coating. The first machining example is an outer circular cutting of an input shaft (low alloy steel, HB270) that requires high tool wear resistance. Machining (cutting conditions: Vc=250m/min, f=0.36mm/r, ap=0.5mm; wet cutting); the second processing example is for the crankshaft (low alloy steel, HB300) end face with large discontinuous part/ Intermittent cutting of the outer circle (cutting conditions: Vc = 180 m / min, f = 0.4 mm / r, ap = 3 mm; wet cut). The results of comparison with the original coating materials show that the black gold CVD coating improves the anti-plastic property of the cutting edge during continuous cutting, and improves the chipping resistance of the cutting edge during intermittent cutting.
In the milling process that belongs to interrupted cutting, the advantages of black gold CVD coating materials are further exerted. The main application area of ​​the new coating material GC4240 developed for the milling of steel parts is the removal of black skin and unstable intermittent processing. The machining results show that the tool's fracture resistance is greatly improved; the coating thickness of the new coating material GC3220 developed for milling gray cast iron is increased compared with the original coating, while maintaining good fracture resistance. , to achieve high-speed and efficient processing of cast iron.
(4) Characteristics of bronze multi-layer PVD coating
In recent years, low-resistance milling cutters have become mainstream, and the development of large-angle milling cutters is prevalent. Due to the large back angle of the insert, the milling insert material is required to have higher toughness. Compared with CVD coatings, PVD coatings can also be applied on sharp cutting edges, so PVD coatings with good fracture resistance are more suitable. Bronze multi-layer PVD coatings are coating materials developed for milling.
In general, since the matrix and the coating of the PVD coating are susceptible to chemical diffusion, the bonding strength is lower than that of the CVD coating, and the coating is easily peeled off. From the point of view of the residual compressive stress generated in the coating, it is mainly that the coating near the tip is prone to flaking. Therefore, it is quite difficult to increase the heat resistance by increasing the thickness of the coating. The bronze multi-layer PVD coating developed to improve the resistance to flaking and heat resistance is characterized by a coating thickness of several micrometers and an ultra-multilayer structure comprising thousands of layers of high heat resistant TiAlN coating. Compared with TiN and TiCN coatings, TiAlN coatings have better heat resistance, but they are not easy to maintain their peeling resistance. The practical coating thickness is 1~2ïm. Sandvik has multilayered TiAlN coating. It can effectively prevent the crack propagation of the coating caused by the cutting impact, and even if the thickness of the coating is increased, the coating peeling caused by the cutting impact does not occur.
(5) Processing properties of bronze multi-layer PVD coating
The following is an example of machining a steel part with a GC1030 coated tool to illustrate the performance of this multilayer coating. Milling processing difficult to work hard and hard material mold (cutting conditions: workpiece material: DAC3 (HRC41); cutting speed: Vc = 90m / min, feed per tooth: fz = 0.15m / tooth; number of teeth: z = 1; Machining allowance: ap = 2mm, radial machining allowance: ac = 20mm; down milling, dry cutting), compared with the processing performance of the original single-layer PVD-TiAlN coating material. Compared to the original coating, the GC1030 coating showed high resistance to spalling and heat. In addition, the coating also exhibits excellent cutting performance in the processing of stainless steel and titanium alloy which is more prone to sticking of the knives and coating peeling than the cut steel, and is a universal coating material which is widely used in various fields.
In the fall of 2006, GC1020, a new material for cast iron milling, was assembled from a cemented carbide substrate that is most suitable for cast iron processing and a newly developed coating. The machinable cast iron machining with poor machinability and high cutting resistance and the blade peeling due to coating peeling Cast iron wet cutting, which is prone to hot cracking, exhibits superior cutting performance than the original material.
Sweden Sandvik develops and produces a new generation of coated inserts based on high-precision and efficient cutting and market diversification, including two PVD coating materials for turning and milling steel and cast iron and three CVD coatings. The materials are as follows.