With the development of modern science and technology , a variety of engineering materials with high hardness are increasingly being used, and the traditional turning technology is difficult or impossible to achieve competent processing of certain high hardness of the material . Coated carbide , ceramics , PCBN cutting tools and other superhard materials because of its high temperature hardness , wear resistance and thermal chemical stability, which provides a basic prerequisite for the cutting of high hardness materials and production and achieved remarkable results.
Superhard tool and choose
Materials and structures and tool geometry parameters superhard cutting tool is used to achieve the basic elements of hard turning , therefore , how to choose the super-hard tool materials , design a reasonable tool geometry parameters on the stability of the structure and achieve hard turning is very important.
Coated Carbide
The toughness of cemented carbide cutting tools coated with a wear layer or multilayer good TiN, TiCN, TiAlN , and Al3O2 , etc., the coating thickness of 2 ~ 18μm, the coating typically has a ratio of the base tool and workpiece materials a much lower thermal conductivity, and a reduced thermal effect of the tool substrate ; other friction and can effectively improve the adhesion of the cutting process , to reduce the generation of heat cutting .
Coatings can be generated into a physical vapor deposition method (PVD) and chemical vapor deposition (CVD) 2 species. PVD coating (2 ~ 6μm) include TiN, TiCN, TiAlN , etc., which are constantly increasing component , such as TiZrN. TiC and TiN coatings maximum pressure can be achieved , respectively 3580MPa and 3775MPa, TiAlN coating due to the lack of reliable data and elastic modulus of the compressive stress are not accurate , high-speed cutting test results show that the best performance of TiAlN . Figure 1 is a case of three kinds of these coating hardness changes with temperature , the maximum hardness at room temperature greater than [Y; when , TiAlN coating hardness than TiN and TiCN coating. Figure 2 shows the processing of nickel-based superalloy Inconel178 with two kinds of cutting tool life under 193.5m/min v1 = v2 = 380m/min and conditions , experiments show TiCN and TiAlN coated cutting significantly better than TiN coating.
Although PVD coating exhibits many advantages, but some , such as Al2O3 and diamond coatings tend to adopt CVD coating technology. Al2O3 is a strong and oxidation resistant coating , it is possible to heat generated by the cutting tool body and isolated. Coating by CVD techniques , the advantages of various coatings can also be integrated in order to achieve optimum cutting performance to meet the needs of cutting . For example . TiN has low friction characteristics, organizations can reduce the loss of coating , TiCN reduce flank wear , TiC coating high hardness , Al2O3 coating has excellent heat insulation effects.
Compared with coated carbide tools carbide cutting tools , both in strength, hardness and wear resistance are greatly improved. Turning hardness HRC45 ~ 55 artifacts , low-cost high-speed turning carbide coating . In recent years , some manufacturers use other methods to improve the coating materials , the performance of coated tools has greatly improved. Some manufacturers such as United States, Japan 's Swiss AlTiN coating materials and coating patented technology to produce new coated blade , hardness up HV4500 ~ 4900, the hardness of tool steel can be cut when 498.56m/min speed HRC47 ~ 58 's . Still does not reduce the hardness in turning the temperature up to 1500 ~ 1600 ° C , the oxidation, blade life is 4 times the normal blade coating , while the cost of only 30 %, and good adhesion.
