Research on the Performance and Improvement of Electroplated Diamond Tools
0 Introduction
Due to its excellent physical and chemical properties such as high hardness, high strength, high wear resistance, and a small linear expansion coefficient, diamond is used to make diamond tools for processing hard and brittle difficult-to-machine materials. The preparation of diamond tools by electroplating involves the electro-deposition of metal to consolidate loose diamond particles in the electroplating layer, giving the diamond particles cutting ability. The production of diamond tools by electroplating has a low manufacturing temperature, avoiding thermal loss to the diamond. Additionally, it features simple production processes, low equipment investment, short manufacturing cycles, easy forming, and the ability to repair. Therefore, diamond tools, including electroplated diamond products like grinding wheels, grinding heads, assorted files, material removal knives, dressing rollers, geological drill bits, reamers, internal and external circular cutting discs, reamers, and wire saws, are widely used in industries such as machinery, electronics, construction, drilling, and optical glass processing [1-3].
Currently, the main problem encountered domestically and internationally when using the electroplating method to prepare diamond tools is the low bonding strength between the coating matrix metal and the diamond particles. During use, the diamond particles can easily become loose and fall off under force, resulting in a short service life. The primary reason for these phenomena is the low manufacturing temperature when preparing diamond tools by electroplating, which makes it difficult for the diamond particle surface to be wetted by common metals. This not only prevents strong chemical bond formation but also often results in gaps. Additionally, due to the influence of the electroplating process, there are limited types of coating metals available for diamond tools (only a few metals such as nickel and chromium and their alloys), unlike the wide range of metals used in hot-pressed tools.
In response to these issues, various measures have been adopted to enhance the bonding between diamonds and the coating metal. This article comprehensively introduces methods developed in recent years both domestically and internationally to improve the performance of electroplated diamond tools and categorizes them to provide a detailed and clear understanding.
1 Improving the Matrix Material
In electroplated diamond tools, the coating supports and bonds the diamond, referred to as the matrix or base metal. It determines whether the diamond particles can fully exert their cutting function. Generally, it is required to meet performance requirements such as high hardness, high wear resistance, and relatively high toughness. Therefore, people first considered improving the performance of the matrix material to enhance diamond tools.
1.1 Alloying of Matrix Metal
Although single-layer coatings (such as nickel) have relatively high strength, especially toughness, they generally have lower hardness, leading to the adoption of alloy coatings.
1.1.1 Ni-Co Binary Alloy Coating [1-5]
Cobalt not only enhances the strength of nickel metal (the compressive strength of the nickel-cobalt alloy matrix is 1600 MPa) but also improves the heat resistance of the matrix metal. At 800°C, the ultimate tensile strength of the NiCo binary alloy matrix metal is 500 MPa, and it also enhances the toughness of the matrix metal.