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TD Coating Technology

Hits: Date:2011/10/28 Font Size:14px 12px
TD coating technology(2007/3/28)
TD coating is abbreviation for thermal diffusion carbide coating process. But this kind of technology was firstly developed by Toyota Central R&D labs., Inc. and was applied for patent. So this technology is called Toyota diffusion process too, and the abbreviation is TD process or TD. This technology is called metal penetration in melted salt. No matter what it is called, the method is the same. The tools or models are put in melted borax which is blended with other elements. The metal carbide coating is formed on surface of tools through diffusion process in high temperature environment. The metal carbide could be vanadium carbide or niobium carbide or chromium carbide, and could be compound with two kinds of metal carbide or more. But the vanadium carbide coating is more often applied. The main features of vanadium carbide are follows:

1.The TD coating hardness could reach from HV 2800 to HV 3200. The TD coating hardness is more than nitriding and plating chromium, so the TD coating has better resistance of wearing, galling, and corrosion.

2.Because of diffusion process the TD coating metallurgy welding on substrate surface. The binding power of TD coating is more than PVD or CVD. This quality is very important in some kinds of forming dies.

It is proven by a lot practicing that TD coating is one of the most economic and the most effective method to solve the problem about galling. TD coating can extent tools life by more than three times, even more than thirty times. So It is utmost valuable.

TD coating was gradually introduced into some countries from Japan in 80s. As there were different situation in different countries, TD coating was succeeded in some countries and was lost in other countries. This technology is widely used by Japan, American, and Korea now. It was studied in our country in 70s. There have been more than thirty domestic institutions to study this technology by now. There have been hundreds article about TD coating published and several patents about TD coating. It is believed that some institutions still study this technology now. In fact, the criterion about TD coating was found in our country in middle 80s. The criterion name is metal penetration in melting borax, JB/T4218-946, which was authorized on October 25, 1994. Because of lack of experience of long term and stable production, there were a lot of problems in practice application. Though there are so many people who are interested in this technology, no one can introduce TD coating into practice production.

We started to study TD coating in 1991. Our technology come nature with so much lost and success, with hard studying and actual production. We are forming our own unique technology system. We became first domestic company which could provide TD coating service in 2001. We have advantage to control distortion and crack, comparing with abroad TD coating. We have succeeded in applying TD coating to drewing dies, bending molds, burring dies, forming rolls, cold forging dies, blanking dies, powder molds and some of parts, which are belong to automobile, home appliance, hardware, tube, metallurgy sectors and etc. So we get a lot of experiences about TD coating. We solve the problem about galling through our TD coating. And the tools or molds life are great increased, even instead of abroad tools or molds. The results are very excellent.

TD coating process

TD coating process is difference, depend on metal and place. But the base process is same. The tools are put in borax compound. Keep from 850 to 1050℃ for from 2 to 12 hours. After the TD coating is formed, the tools are chosen proper way to cool down according to its feature. Generally quench, but there are some exceptions. Then conduct post-treatment, for example, tempering, clean, size adjustment, polishing and etc.

Main index and feature for TD coating
1.High wearing resistance and galling resistance with TD coating hardness from HV2800 to HV3200.
2.Density and smooth TD coating with thickness from 0.004 to 0.02 mm.
3.High corrosion resistance.
4.Metallurgy binding onto and into substrate.
5.Repeat application.
Proper metal and its application scope for TD coating.

Proper metal:
As long as tools contain proper carbon, the TD coating can be formed. For example, the different kinds of metal and carbide that its carbon content is more than 0.3% are proper. It’s necessary for metal to be deliberate chosen for TD coating, if the good effect has to be gotten. That depends on application environment.
Application scope

Proper metal:
TD coating can solve these kinds of problems:

1.Galling and adhesion are caused by friction between products and molds or products. For example, It occurs in drawing, extent, bending, burying, rolling mold for the steel plate or other nonferrous metal processed, and tools surface which move relatively. TD coating is one of the best way to solve theses kinds of problems.

2.Exceeding tolerance of molds or products is caused by wearing. For example, blanking dies, cold forging molds, powder molds and some of parts. Their life can be increased by several times, even more than thirty times.