Nano Diamonds in the Mechanical Industry

（1）Nano Diamond Powder Composite Coating

Nano Diamond Powder Composite Coating Technology is one of the key technologies for product manufacturing. Through surface coating, the surface of the product can be protected by a protective layer of controlled composition and organization, which significantly improves the service life and reliability of the product. For example: marine platforms, large-scale open-pit mining, metallurgical and petrochemical production equipment in harsh environments, the use of long-lasting composite protection can be used in the use of the period of 5~10 years of internal corrosion; machinery industry, the use of a large number of widely used cutting tools, molds, pumps, shafts, valves, the use of the surface strengthening, the service life can be increased by 3~5 times.

Nano Diamond Powder Composite Coating Technology is an effective means to improve quality, efficiency, energy saving, material saving, environmental protection and economic efficiency. Statistics show that machinery manufacturing in about 1/3 of the energy directly or indirectly consumed in wear and tear, abrasion caused by loss, the world’s steel production of 1/10 loss of rust and other corrosion, corrosion and abrasion to the national economy caused by the loss of a staggering, according to the United Kingdom and the United States of America and other countries to investigate the national economy 2% ~ 4% of the total value of the output due to loss of corrosion, the country’s annual loss due to corrosion caused by the loss of at least 40 billion yuan, according to the survey of 27 provinces and cities of China’s about 400 mechanical industrial enterprises, the loss of 11.6 billion yuan a year due to corrosion. It is understood that the world’s annual metal corrosion loss of about 150 billion U.S. dollars, China’s annual loss of 150 billion yuan, and metal plating is one of the ways to solve this technical problem.

In recent years, the high hardness and corrosion resistance of diamond powder for composite plating layers have attracted increasing attention. However, since the general diamond powder particles are micron or submicron, the particles are relatively coarse, the coating organization obtained is difficult to meet the requirements of precision instruments, high gloss surface, fine processing and higher wear resistance. With the rapid development of nano diamond powder production technology, especially the emergence of 2-12 nm diamond powder, the use of nano diamond powder to form a composite layer is expected to make up for this deficiency. Brush plating technology is a new type of surface modification technology developed on the basis of electroplating technology in recent years, which can solve the problems of mechanical parts repair that are difficult to be solved by other technologies. The Open Research Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, in cooperation with the Department of Materials, Lanzhou University, investigated the tribological properties of the composite nickel-brush coating containing nano diamond powder, and the results showed that the coating has excellent friction and wear-resistant properties, and the friction and wear-resistant properties increase with the increase of the content of nano diamond powder black powder in the test range.

Effective protection can reduce corrosion loss by at least 15% to 35% and wear loss by about 1/3. In addition, because the surface coating is very thin, the surface coating and modification often use very little material to significantly improve the performance of corrosion and abrasion resistance, etc., which has obvious economic benefits in saving valuable materials and reducing manufacturing costs. For example, for worn out molds, crankshafts, guides, cylinder liners, cases, shafts, bearing seats, bucket teeth, linings and other parts, as well as crawler vehicle parts, the use of brush plating technology to carry out normal maintenance work, with great economic benefits.

After studying the tribological properties of nano-diamond powder composite chromium plating layer, it was found that the addition of nano-diamond powder to the composite plating layer can form a homogeneous and dense composite plating layer. The addition of nano diamond powder can refine the grain size of the plated layer, which has the effect of diffusion strengthening and improves the hardness of the composite chromium plated layer. Under oil lubrication conditions, the addition of nano diamond powder significantly improves the wear resistance of the layer, and the best results are obtained at a layer thickness of 27 μm, with a 12-fold increase in wear resistance compared to pure chromium plating.

Nano-composite plating is a deposition technique in which insoluble solid particles of nano diamond powder are added to the plating solution to form a homogeneous suspension, and the solid particles are co-deposited with metal ions to obtain a composite plating layer. The nanoparticles are fully dispersed by suspension technology, and the nano diamond powder composite layer obtained has excellent properties such as high abrasion resistance and friction reduction. The hardness of nanocrystalline diamond powder composite layers can reach HV700 to 1100, and the abrasion resistance is superior to that of Cr15, normal nickel plated layers and micron diamond powder composite layers. The coefficient of friction is only one-third of that of conventional coatings. The unique self-lubricating effect increases the wear life by 2-5 times. It can be widely used in the surface treatment of precision wear-resistant parts in various industries, replacing the original chrome plating, nickel plating and other processes. The application effects are shown in Tables 1-3.

Table1 Experimental Results of Chrome Coated Drill Bits Containing Nano-level Diamond Powder

 Table2 Experimental Results of Chrome Diamond Powder Coating on Press Molds

Relative life compared to nitriding, carburizing, Chromium plating and special steel tools.

Table3 Chromium Diamond Powder Coating Stamping Tool  (negative mold, positive mold)

Experimental results during sheet stamping