Why do Carbide Tools Achieve Higher Metal Removal Rates?

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1. Production of carbide inserts

As more and more advanced industrial equipment with cutting-edge automation and computer control enter the cemented carbide manufacturing enterprises, the technical control of the cemented carbide production process is becoming more and more stable, controllable and reliable. The result is that the machinability of the produced inserts is becoming more and more consistent, the machining results are predictable and do not vary depending on the insert batch number, and the new technology also enables sintered inserts with narrower dimensional tolerance bands and higher precision , the performance of cemented carbide inserts has been greatly improved.

Today, a typical blade press is often a computer-controlled, highly engineered device. Certain press designs also allow for multiaxial pressing. Extraordinary advances in pressing technology have made it possible to produce blades with complex shapes, such as blades with very large differences in tip height. The advanced pressing technology ensures that a more optimal blade shape can be obtained, which not only ensures a smooth blade surface and a stable blade production process, but also improves the precision level of the blade surface. In addition, the application of modern computer-aided design and manufacturing technology (CAD/CAM) has also brought benefits to the production of blades, making it possible to improve the level of blade design and obtain better shape and precision of pressed mold parts. With the ability to simulate the pressing production process with the final sintered product as the guide, the pressing and sintering results can be modified from the design point of view at the initial stage of design to facilitate the successful development of new inserts.

The mastery of advanced technology in insert sintering also helps to improve the quality of the inserts during the production process. Process control is carried out during the sintering process to obtain a graded cemented carbide matrix with a non-uniform structure, ensuring that the alloy surface has a thin cobalt-rich layer. The cemented carbide substrate with a gradient layer can block the development of surface cracks and ensure that the cemented carbide substrate has better resistance to brittle cracking and damage. Today, graded carbide substrates are often used in turning tools.

2. Development of coating technology

The introduction of coated cemented carbide and the continued development of the field have significantly increased the cutting speed of tools. Coating technology has continued to develop mainly along two basic directions: chemical vapor deposition (CVD) and physical vapor deposition (PVD). A major development in CVD coatings came from the introduction of alumina ceramic coatings. The alumina ceramic coating has excellent thermal insulation properties, wear resistance and chemical stability at high temperatures, which allows the tool to be machined at higher cutting speeds.

PVD coatings thus offer a whole new class of nanocoatings with higher wear resistance. Compared to the conventional PVD coating method, the coating shown in Figure 2 is composed of a coating with a maximum value of 50 nm, which has been shown to greatly improve the bonding strength of the coating.
The development of modern technology allows operators to coat the blades with both CVD and PVD coatings, and the composite coating method has better control over the coating properties. For example, Iscar cemented carbide grade DT7150 is a medium temperature chemical coating (MTCVD) and TiAlN (PVD) coating on a ductile substrate. This coating was originally developed to increase the productivity of hard cast iron with special applications.

Another major advanced manufacturing method of blade technology is coating post-processing technology. For example, ISCAR’s Beam Magic Technology (SUMOTEC) uses a method of post-processing the surface-coated inserts. Cutting-edge beam magic coating post-treatment technology increases the strength and wear resistance of cemented carbide grades, resulting in higher productivity. For CVD coatings, internal stress is generated due to the difference in thermal expansion coefficient between the cemented carbide substrate and the coating. The PVD coating has the problem of surface droplets remaining. The above factors negatively affect the coating and thus shorten the insert life. Using the Beam Magic coating post-treatment technology significantly reduces or even eliminates the effects of these negative factors, resulting in a significant increase in productivity in addition to higher tool life.

Inconel 718 is a nickel-based superalloy and is widely used in applications where high temperature and corrosion resistance are required for parts and components. The material has been widely used in the aerospace industry, such as being made as a hot end component of an aircraft engine, and has also been made into a variety of components in the petroleum industry.

The microstructure of Inconel 718 shows an austenitic structure with high tensile strength and yield strength. The main problem encountered with machining Inconel 718 is the very high temperature of the insert cutting edge. This is due to the fact that the 50%~55% high nickel and 17%~21% high chromium contained in the material act as abrasives to wear the blade during processing, resulting in blade failure due to high wear rate, chipping, groove wear and breakage. Even at low cutting speeds, these factors result in reduced tool life and severe plastic deformation of the cutting edge.

Another complicating factor in the processing of Inconel 718 is the tendency for its properties to change due to residual stress and self-hardening effects due to metallurgical sensitivity during processing.

The continuous advancement of cemented carbide insert production technology and the combination of more diverse surface treatment methods make the indexable inserts produced can provide a more suitable solution for the modern metal processing industry to meet its high-efficiency processing needs.

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