[Abstract] diamond film is synthesized by chemical vapor deposition method was a holocrystalline polycrystalline pure diamond materials, is an ideal material for making tool. In this paper, the research progress and application status of CVD diamond coated cutting tools and thick film welding tools are briefly reviewed.

1 Introduction

With the rapid development of automobile, aviation and aerospace industry, material of light weight, high specific strength increasing, nonferrous metals and alloy, carbon fiber enhanced plastic, glass fiber reinforced plastic, fiber reinforced metal and graphite, ceramics and other new materials in the industry get more and more widely used, ordinary high-speed steel and hard alloy cutting tool in machining of these materials, the defect is obviously exposed. Also the advent of modern integrated manufacturing systems, computer integrated manufacturing system, as well as mechanical processing is moving in the high precision, high speed, high productivity cutting direction, also set the very high request to the performance of the cutter. It is an inevitable trend to develop a super hard material tool which has excellent wear resistance and can be stabilized for a long time. Diamond has many excellent properties, such as ultra high hardness, high thermal conductivity, Gao Guangxue transmittance and excellent electrical insulation, is known in the material is difficult to compare the ideal material for the manufacture of cutting tools. Due to the limited natural resources, and the price is expensive, can not be used in industrial scale. Polycrystalline diamond with high temperature and high pressure and method of manufacturing tools (PCD) binder component containing 5%- 10%, this

The surface quality of the processed material obtained is lower than that of the natural diamond cutting tool, and the PCD tool can not be made into a complicated shape. Chemical vapor deposition (CVD) diamond is pure diamond polycrystalline structure, no metal binder component, theoretically it is closest to the natural diamond, a new cutting tool material, and the performance of PCD close to (or slightly lower than the PCD), but its cost is far than PCD low, and can obtain a uniform coating on the complex shape. The main properties of CVD diamond and its comparison with the properties of pure natural diamond are shown in table 1. Currently CVD diamond tools are mainly divided into two categories, namely, diamond film coated tools and diamond thick film welding tool. CVD diamond film coated tools is particularly suitable for processing non-ferrous metals and alloys, non metallic materials, composite materials and other materials hard to be machined, and CVD diamond thick film welding tool can be used for precision and ultra precision cutting processing. In this paper, we will review the research progress and application status of two kinds of CVD diamond tools.

Table 1 Comparison of the properties of pure natural diamond and CVD diamond at room temperature

2 CVD diamond film coated tool

CVD diamond film coated tools is generally by chemical gas phase deposition method in high strength and good toughness of cemented carbide substrate deposition thickness less than 30 μ m of diamond thin film manufacturing and into. It can be learned from the manufacturing method that CVD diamond film coated tools have the properties of hard alloy and diamond film.

(1) adhesion between diamond film and cemented carbide substrate

The diamond coating can significantly prolong the service life of the cutter and improve the use efficiency of the cutter. However, the shortcomings of the poor adhesion between diamond film and cemented carbide substrate limit the large-scale industrial application of CVD diamond coated carbide tools. If the adhesion between the film and the substrate is small, in the cutting process, the cutting force of the diamond film is easy to fall off, so as to seriously affect the coating tool's use effect and life. So at present, the research of CVD diamond film coated tool is mainly around the problem of adhesion. The difficulty of enhancing adhesion between diamond film coating and cemented carbide substrate comes from cemented carbide. Transition elements (Fe, Co, Ni) under the conditions of high temperature and high pressure can promote the transformation from graphite to diamond, so it can be used as a catalyst for high temperature and high pressure synthesis of diamond. However, under low temperature and low pressure (CVD diamond growth conditions), they promote the growth of graphite [2], the adhesion of diamond film and hard alloy substrate is very poor, can not be applied. So in recent years, researchers have tried every means to improve the adhesion between diamond film and cemented carbide substrate, and the measures taken include: applying a wide variety of transition layer; mining

Acid etching and etching method for removal of cobalt; to develop the non - cobalt or cobalt containing a small amount of cemented carbide substrate; mechanical or heat treatment, excimer laser irradiation on hard alloy substrate surface; C60 and carbon nanotubes reinforced cemented carbide substrate nucleation. After continuous efforts, to solve the basic problem of adhesion of the diamond film and cemented carbide substrate, although there is still room for greatly improved adhesion, but diamond film coated cemented carbide cutting tools have been listed, and has in the graphite, composite materials, high silicon aluminum alloy difficult processing materials processing success.

Application status of (2) CVD diamond film coated tool

In the late 20th century, appeared abroad, can be used for industrial production of diamond film coated tools in large quantities of equipment, the time can be deposited hundreds of hard alloy bit or blade, opened the prelude of the diamond film coated tools industry. Some companies specializing in the production of diamond film coated tools have emerged in foreign countries. In some developed countries, diamond coated cutting tools are extremely active.

Manufacture of 3.CVD diamond thick film welding tool

CVD diamond thick film welding tool is chemical vapor deposition thickness more than 300 μ m self standing diamond thick film after cutting welding and the tool base on manufacturing. CVD diamond thick film welding knife