PVD coated ultrafine cemented carbide

With the increasingly fierce competition in recent years, higher requirements have been put forward for the manufacturing industry. In the field of cutting, high speed and large feed machining are used to improve machining efficiency and shorten machining time; Use precision tools to achieve high-precision and high-quality processing to improve added value; Extending tool life to reduce tool cost; The use of new technology tools to change the processing procedure (from grinding, EDM to cutting) and other aspects, machining users have put forward higher and higher requirements, and cutting tools have played a very important role.

Among all kinds of tool materials, PVD coated ultrafine cemented carbide has made significant progress. Its excellent performance has greatly promoted the development of drilling processing technologies such as molds and auto parts. Up to now, CVD cemented carbide materials have also played an excellent role in turning. The "PVD coated ultrafine cemented carbide" technology and new processing examples are introduced below.

Cemented carbide is a composite material with Wc (tungsten carbide, high hardness brittle material) as the main component dispersed in Co (cobalt, low hardness high toughness material), which is one of the hard materials with both hardness and bending strength. Among the current materials used for cutting tools, the cemented carbide coating materials that can withstand high-speed cutting such as Al2O3 or (Ti, Al) N coating on the above cemented carbide through CVD (chemical coating method), PVD (physical coating method) occupy the main position.

The properties of cemented carbide are determined by such factors as Co content and Wc particle size. The hardness, compressive strength and rigidity of cemented carbide with less Co content are higher, but the impact resistance value is lower; The hardness and bending strength of cemented carbide with smaller Wc particles are higher, but its toughness is lower.

Ultrafine cemented carbide is an alloy material developed for simultaneously improving hardness and bending strength. Compared with ordinary cemented carbide, it has the characteristics of high strength at the same hardness and high hardness at the same strength. Wc particles of common cemented carbide are 1-6 μ m（ μ= 10-6), Wc particle of ultrafine cemented carbide is 0.6 μ M or so, because it is very small, the thickness of the Co component that plays a bonding role around the Wc particles is thin. At the same time, the small breaking initial size makes the bending strength high. Ultrafine cemented carbide has been used in integral cemented carbide tools such as fine diameter drills and end mills, and recently it has also been used for indexable inserts. However, although ultrafine cemented carbides exhibit excellent properties at low temperatures, they can easily experience chronic deformation at high temperatures. When used at high cutting speeds, plastic deformation, increased wear and other phenomena may sometimes occur. Please pay attention.

However, with the rapid development of micro WC powder manufacturing technology of powder manufacturers and cemented carbide manufacturers in recent years, the size is 0.4 μ WC superfine cemented carbides of about m also appear in the market.

PVD is the abbreviation of Physical Vapor Deposition. It is different from CVD gas that generates chemical reaction to form surface film at high temperature. It uses physical methods such as electric energy to make metal vaporizer generate ions for coating. Compared with CVD, PVD coating has the following characteristics.

PVD can be coated at low temperature compared with CVD, and the loss of cemented carbide base metal is small, so the base metal can be selected during coating; CVD coating film has tension, so it has disadvantage in defect resistance. In contrast, PVD coating produces compressive force, which is conducive to defect resistance, and can be used in the manufacture of sharp cutting edge tools.

PVD coating can be used in the processing form that gives full play to the above advantages. The details are as follows:

Integral carbide tools with sharp cutting edges are required;

The blade for plane milling cutter with strong defect resistance is required;

Low speed cutting blade that is easy to crack due to welding;

High speed steel cutting tools with lower hardness of base metal at high temperature.

In particular, the research and development of PVD coating for solid carbide end milling cutter has made significant progress. In the past, TiN or TiCN coating was the mainstream product, but the appearance of (Ti, Al) N coating in the early 1990s made the performance of solid carbide end milling cutter greatly improved. In particular, the (Al, Ti) N coating rich in Al realizes the direct processing of quenched steel by greatly improving the surface film hardness and oxidation resistance, which is a technological innovation in die processing. At present, the development of special coatings for different purposes, such as coatings for processing ultra-high hardness materials and coatings for mild steel processing, which are about HRC60, shows a diversified trend.