FAQ

1.  How much do dies & jigs need to be polished before the TRD process?
All we ask is that you use 320 grit on the working surface.  Teikuro will make sure that the rest of the polishing is taken care of, up to 1 micron or less finish.  It is essential that the die surface is prepared properly prior to the TRD process for maximum performance.  Our expert die polishers will finish up quickly, beautifully, and most importantly professionally.  We may ask the customers to lap the die surface if precise dimension control is required. 

2.  Can you remove previous coatings before applying the TRD coating?
Yes, we can remove any kind of coating safely and effectively.  We have a unique coating removal method, which minimizes the surface damage.  We do request that the customer specifies the previous coating so that we are able to use the correct removal process.  This will also allows us to speed up our process.

3.  How much material will be removed during coating removal and die polishing?
We remove whatever the coating thickness is and another .001-.0015” during polishing to obtain a mirror finish on the die surface.

4.  How will the TRD coating adhere to a weld repaired surface?
Generally the TRD can be processed over a welded surface and has strong adhesion unless the welding rod is incompatible to the TRD.  (Please contact us for recommended welding rods)

5.  Will cracking occur on a welded surface after the TRD process?
First of all, any welding job on the working surface must be properly done with a crack free condition.  Cracking may extend or open up after the TRD process.  Fully annealing the die before applying the TRD process will always minimize the risk of cracks occurring on the welded or non welded surface. (This process may require a longer turn around time.)  Teikuro is fully capable of replacing a weld and grinding it down and refinishing for better results.  Please contact us for more details..

6.  Can unhardened die steel be used in the TRD process?
Certainly, the TRD process will not only apply a coating, but will also harden the die simultaneously.  You can finish machining dies as green and have them TRD coated.  This will save you time and money.  (Please contact us about pre-coating dimensions)

7.  Why is the TRD coating sometimes a different color when it is returned?
The TRD coating has a beautiful deep or blackened shinny steel color with a lap finish after the process.  Without polishing the coated surface will look black.  This black layer occurs on top of the vanadium carbide.  This reaction occurs when the die is exposed to oxygen upon leaving the furnace.  The depth of this reaction is within a unit of angstrom, and does not affect the quality of the TRD coating.  The color is also changed to a light blue of dull yellow when the dies have to be post hardened in a vacuum furnace.  Vacuum hardening increases the hardness of the die, but does not affect the quality of the TRD coating either.

8.  How do I know if the TRD coating is still on my die?
There are some simple tests tat can be applied.  Run a file across the surface of your die, if there is no resistance then the coating still exists.  Run a sharp edge of the die across a piece of glass, if the glass is scratched the coating still exists.  Applying copper sulfate to the die is also an easy test.  If the surface turns a red color(copper color) this signifies where the TRD coating is missing. 

9.  Which is better the TRD coating or Teikuro chrome plating?
Teikuro Chrome plating is widely used and has an excellent reputation throughout the world.  This process is mainly used for mid to larger sized automotive stamping dies.  These dies run a thinner sheet metal up to 1.5 mm-2 mm.  Anything above 2mm, all type of HSLA material, and stainless sheet metal forming we recommend the TRD coating.  This process has a stronger adhesion and a higher adhesion resistance under a more sever application.  The size of the die, the material, and the shape of the die are all important factors in determining which product to use. 

10.  What is the maximum size of die that can be processed?
As long as the die can fit into our TRD pots (dia. 26” X L 60”).  However, the actual maximum size may need to be a little smaller.  There are no minimum size limitations.  The heaviest die ever processed at Teikuro TRD was 800 lbs. and the smallest was less than .1 lbs.

11. Why Teikuro TRD?
We are not just a surface treatment company.  We have many years of experience in the die business. (40 years of chrome plating)  We have the knowledge to process your dies so that they perform beyond your expectations.  We have die knowledge, experts in die repair and die finishing, complete technical support, an excellent coating service in both TRD and Chrome Plating, and we also employee Dr. Arai, who has practical experience on hundreds of dies throughout the industry. Together all of these will allow your die to have great success.

12.  Can we obtain information on the principle of the TRD process, the mechanism of VC growth, the characteristics of substrate materials using the TRD process, and the practical application data?
Dr. Arai, the inventor of the TRD process and Technical Director of Teikuro Corporation is also known as a specialist of tool steel and several surface treatments.  He has also published more than 300 scientific papers and essays.  We are able to provide information to those that are interested in the TRD process.

13.  How long has the TRD coating been used in the industry?
The TRD coating (aka. TD-Toyota Diffusion) was developed in 1970 and began its use in the Japanese automotive industry.  In the early 80’s it was introduced to Asia and Europe. It was finally introduced to the USA in the late 80’s.  It has been widely used and has contributed to various industries in the world. 

14. Are there any differences between the TRD and the TD processes?
They are exactly the same process.  The TD process stands for Toyota diffusion Process.  This is the “brand name”.  The TRD process stands for Thermal Reactive Diffusion & Deposition.  This is the scientific name.  This is similar to the comparison between the PVD and the CVD processes.

15. What are the advantages of the TRD process?
The TRD process is the world patented technology developed at Toyota Central Research and Development Labs by Dr. Toru Arai.  The TRD process makes it possible to easily obtain a “Pure Carbide Layer”.  This is a fine but thicker layer compared to other coatings.  It also adheres more strongly to the substrate material.  This layer causes the die to have a longer life especially under severe conditions.

16. Why are super hard coatings like TRD, CVD, and PVD popular among the industries?
Mankind has used steel since the Iron Age and has continued to improve it along with the evolution of the industries.  We found that the more hard carbide particles in a tool steel provided, the better the abrasive resistance.  As a result, “High Speed Cutting Steel” was developed in the late 19th century.  However the high speed steel contained only 20% carbide.  “Powder high speed material” introduced 40 years ago contained a maximum of only 30% carbide.  “Tungsten Carbide” (WC) material (Cemented Carbide) was developed.  This material contained 80-90% carbide, but had poor “machine-ability”.  It became very brittle and this restricted its use. 

Finally super hard thin coatings were introduced.  They were superior to WC and contained 100% carbide, nitride, or other ceramic substances.  It was surely innovative, revolutionary, and benefited the industry world.

17.  Why use TRD over other coatings?
Currently Chrome Plating, thermo-chemical treatment like carburizing and nitriding, plasma spray coating, and hard thin coatings like TRD, CVD, or PVD are popular and in wide use.

When your application is extremely severe and requires high wear resistance, TRD should be considered.  Chrome plating or thermo-chemical treatment would not be sufficient.  Plasma spray can be applied thicker than others, and can be used when some damage has occurred as long as there is no quality issue on the products.

Generally PVD has less distortion because of a lower processing temperature, but is definitely inferior to TRD or CVD in the bonding strength to the substrate and coating thickness.  It is not recommended for application where there is an extreme severe condition.

TRD and CVD are scientifically similar. Therefore you have to make the decision based on practical performance, or your provider’s ability.

18. How does the TRD process improve the surface quality of the tools?
The TRD coating improves wear resistance, corrosion resistance, and oxidation resistance. (Selection of carbide layer might be necessary for oxidation resistance.)  It can also help to improve the mechanical property of the substrate material if it is somewhat controlled by the surface quality, such as fatigue strength or heat check.

19. How can the wear resistance of the TRD carbide layer be evaluated?
Wear depends upon the condition of usage.  It does not mean anything if it does not hold up under normal usage conditions.  There are many test results published with general wear condition results, but it is almost impossible to speculate how the die surface will be worn under practical usage.  There is a unique scientific society in Japan which has been eagerly researching the phenomenon of surface abrasion or evaluating the tool material and castings under the practical conditions of the industrial production called “Process Tripology” There are a number of research papers or comments that can be made available upon request.

20. How can the thickness of the TRD layer be measured?
a) Calo Tester- making wear marks over the substrate

b) Scope – Using b ray backward – Scattering Strength

c) X-ray fluorescence analysis

d) Microscopic method over the coated section – Microscope and polishing devise( required not to have round edges at the edge of coating during polishing, otherwise an accurate number will not be measured)

21.  How hard is the TRD Carbide layer and how can it be measured?
Vanadium carbide layer is measured at approximately Hv 3,200-3,800; Chrome carbide (Cr23, C6, Cr7C3C) measures approximately Hv 2,500.  It is considered to be an appropriate value since those values are almost equivalent to the hardness of the carbide grains contained in the tool steel material.  It is always very difficult to measure such a thin layer with such an extremely high hardness.

Sometimes you read an article or data showing Vanadium Carbide has a hardness of Hv 1,500-2,000, which is the measuring result without the consideration of the loading effect.

If the load is too high, measuring devices read the hardness of the softer substrate combined with the VC layer; therefore they are not really representing the real hardness of the VC. Micro Vickers Tester is considered to be the best method since it can apply  less loading (25-50 g) and is not affected by the soft substrate.  It can however only make a small dent which also makes it difficult to measure “real dimension” with an optical microscope, as a result it often reads up to Hv 4000-5000.  Neither number should be taken as a true representation of the hardness of the vanadium carbide.

The hardness should never be considered as a measuring scale for other special properties of the TRD coating, even the hardness is not an effective factor when considering the resistance to adhesive wear.  There is no significant reason for measuring the hardness of the vanadium carbide layer.  It could be used as a scale to see if heat treatment or the diffusion process were properly processed.   

22.    How can the bonding strength be measured to a substrate material?
There is no method to measure the bonding strength.  The scratch test with the critical loading is often used; however there is a big question about this method since there is no plastic deformation of material involved except very special cases and the peeling with continuous loading should be considered to be “Fatigue Phenomenon ” not “Bonding Strength”.

Considering the mechanism of how the VC layer is formed, it is obvious that the TRD coating has exceptional bonding strength and it has been proven with data collected from a number of real applications.

23.  What type of wear is the TRD coating superior to?
The TRD coating has shown its superior wear resistance against scratching, sticking, seizure, fretting wear, corrosive wear, and oxidizing wear.  The TRD coating is carbide formed finely and strongly over the substrate material and is not only hard but chemically stable.

Regarding the cutting tools, especially for high speed cutting of steel,  reaction between the work material and the tool steel causes the failure. In this case, the coatings of nitrides and oxidizes by CVD or PVD are recommended because they have a less reactive property compared to the VC and will bring you a better result.

24. How is the TRD coating in regards to anti-corrosion and anti-oxidation?
It can not be simply explained.  There are various conditions for both corrosion and oxidation.  The carbide structure is chemically stable and tough against a wide range of corrosive atmospheres. It is also superior to any other corrosive protections.  Regarding the anti-oxidizing, the chromium carbide coating will not be damaged under 800-900 degree C in the air.

25. Why is the TRD coating not brittle since carbides themselves are more brittle than the steel?
The thin layer of TRD bonding is very tightly reinforced by the hardened substrate material and does not break up like bulk carbide substances.  Another reason for this could be large residual stress contained in the carbide coating preventing the substrate surface from cracking or breaking.  This also causes the static bending strength, impact strength, and fatigue strength to be enhanced with the TRD process.

26.  What are some of the applications for the TRD coating?
Mainly,

a) General consumable tools.  For example dies, jigs, fixtures, and cutting blades.

b) Machinery parts requiring high performance – Resistance to wear.  For example, contact with metal, rubber, plastic, glass, ceramics, mineral, and even non-metal material like plants.

Records in Japan show that the die is most popular in weight and machine components in numbers.

27.  Is the TRD process effective in a hot environment?
Many people misunderstand that the TRD coating can’t work in a hot environment because VC starts to oxidize at 1020f.  This may not be the case in a real world production.

In the case of hot forging application, the working material is heated up to 1800F (1000C).  However, the actual temperature of the die in use is below 1020F (550C).  Even if the temperature were to rise above 1020F and begin oxidizing, the die would continue to have excellent wear resistance and extend the life of the die.  So, the TRD coating would still benefit you in the end.  The same could be said for the cutting process of hot steel, half-melted glass, or aluminum injection molds.  It is still important to prevent oxidizing the die by using the appropriate temperature, time and gas atmosphere in preheating stage.

28.  Can the TRD coating be applied to a sharp razor like blade?
Yes, you can apply the TRD coating to a sharp blade.  There are many precedents that the TRD coating helps to improve the performance of the razor blade used to cut paper, plastic film, textile, and rubber sheets.  Please contact us if you are interested in this procedure because there are some things that need to be considered, like material type, shape, and post treatment.

29.  Will the TRD coating work with strong mechanical impact condition.
The TRD process is effective for cutting blades used in cutting 1” dia. steel or bigger and also on rotary forging dies.  The TRD (vanadium carbide) coating is reinforced with the substrate material and has great impact resistance.

30. Will the TRD coating be effective against sticking?
Rubber sticking in a rubber forming application and aluminum sticking in aluminum die casting can be minimized with the TRD coating.

31. Will the TRD coating always benefit me?
Yes, you will always have a good result from the TRD coating as long as it is used properly.  The TRD carbide coating (VC) is far superior to any tool steel. Therefore, if you have not seen a significant improvement (10-100 times) you may want to review the design of the die, your process, or the material of the die (process engineering) to see if anything has been done inappropriately prior to the TRD process.  It is easy to say that there was a TRD coating failure, however it would not answer the question of why there was a TRD failure.  It is important to find the root cause in modern industry using process engineering capability.  This is the only way to guarantee your success.  Teikuro is proud of having a wealth of knowledge and experience in process engineering capability in many fields, and is glad to share this knowledge with all of our customers.

32.  What are the most critical points to have the best results with the TRD coating?
The five most critical points for success are surface roughness, having the radii all true and smooth, material hardness, the thickness of the VC coating, and distortion. 

33. What is the most suitable roughness of the VC?
The coating thickness of TRD coating is usually between 0.0006 to 0.0008 inches. The thickness would not affect mechanical property of TRD coating, therefore it will perform very well as long as the thickness is below 0.0008 inches.

34.  How should an R be extended from a flat?
Make sure not to have any edge on the joint between the flat and the R.  Tangent point of the R to the flat surface must be smoothly extended, otherwise seizure, wear and rough surface of formed parts will occur.  We strongly suggest not leaving the shape line below the R.  This could possible extend the life of your die dramatically.

35.  What is the most suitable hardness for a substrate material (Tool steel)?
If the substrate hardness is insufficient and the substrate shows plastic deformation, the TRD layer will probably have small cracks on the surface and will not extend the life of the die.  In this case it is obvious that the die needs to be harder.  What is the best hardness and does a harder die always equal longer life for the die?  Is there also a minimum hardness to be insured?  If the damage only exists on the surface, the substrate hardness may not be the issue.  On the other hand, if the damage is penetrated into the substrate, the hardness should be the issue, and a longer life can be obtained with the higher substrate hardness if the damage is simply caused by material fatigue.  Longer die life can also be obtained with a lower hardness if the damage is caused by brittleness .  To best answer this question is that each circumstance is unique and does not have just one specific answer.  The hardness depends on the specific die and its usage.

36.  What is the most suitable carbide thickness?
Since the thickness of the TRD coating does not affect its mechanical property, there should not be any destruction of the performance of coated parts as long as the coating is thicker than 15-20 mm (.0006”-.0008”)

37. Is there any correlation between distortion and coating life?
If there is large distortion or bending on coated slender punches, this could cause fatigue destruction because of the excess bending stress. Decreased clearance in the stamping dies can  Tighter clearance  in the stamping dies caused by substrate distortion may affect the life of TRD due to the adhesive wear and galling.

38. Is D-2 the only material that will work with the TRD process?
Absolutely not, the TRD process can be placed over any steel, cast iron, nickel, cobalt, or cemented carbide that contains more than .1% carbon.  Furthermore different materials can be processed at the same time as long as the processing temperatures are the same. 

CVD and PVD must process all like materials at the same time.  This can cause a longer turn around time, quality issues, or even turning down a customer’s order.

39.  Can structural steel be coated?
Yes, it can be coated.  The TRD process has been used for millions of automotive parts or machine components made in structural steel  in Japan.  It has also even been used for some type of dies.

40.  Can the TRD process be applied to oil and water hardened tool steel?
The TRD furnace operates at the same temperature as hardening temperature of  steel.  The hardening process takes place when it is quenched in the air, in the salt, or in a high temperature oil furnace in order to reduce possible material distortion.  However those quenching methods are not sufficient when hardening oil/water quenching steel.  They need to be re-hardened by a non-oxygen atmosphere furnace or a carburized atmosphere furnace. Most machine components use this procedure.

41.  Is D-2 the best material for the TRD process?
The tool steel technology is always improving.  10-20 years ago D-3 was being replaced by D-2 all over the world.  D-2 will be replaced with a new and innovative tool steel.  In Japan and Europe an 8% Cr. tool steel is being used.  The most popular is DC-53.  This material has a better machinability, is tougher, and is more easily hardened to the core.  Teikuro has been recommending DC-53 to its customer for use in severe forming die application.

42.  Which is better high speed or tool steel when applying the TRD coating?
Piercing punch or cold forging die is a popular application for the TRD process, but it doesn’t necessarily mean that high speed is superior to tool steel as a substrate material.  High speed is only better for heat resistance or high hardness.  It is more difficult to get hard, has a higher hardening temperature, limited availability in the market, and cost more.  High speed does not always perform better when it comes to wear resistance compared to regular die steel which shows better properties depending on the condition.  If you are considering applying a TRD coating to high speed, hot or warm application such as hot forging process and metal cutting tools would be the only application that would benefit you, since high speed has better heat resistance. 

With High speed steel does not contain cobalt and you only gain 2-3 points on the HRC scale over D-2 or DC-53.  This is not a trade off considering the higher price.  High speeds that contain higher cobalt would gain more hardness like 68-70 HRC and could extend the life of the die for extremely severe conditions, but this is a very rare application.  High speeds in general do not gain sufficient hardness through the TRD process or the CVD process.  This requires vacuum hardening process and  would cause a longer turn around time.  By having this done you take a risk of distorting the die.  For these reasons, die steel is highly recommended for general die application.

43.  What is the benefit of powder tool steel?
Carbide grains distributed in the microstructure of the powder tool steel  are very consistent and extremely fine which provide better mechanical properties and reduce the risk of distortion.  There are more factors that contribute to distortion and it is recommended that you solve distortion problems before you have the TRD process applied to your powder tool steel because of the very high cost of the material.

44.  What are the benefits of powder high speed over conventional high speed?
Powder high-speed steel could obtain sufficient hardness through the TRD process with no post hardening.  Materials without the cobalt should get about 61-62 HRC and material with cobalt should get about 67-69 HRC, thus they can eliminate the disadvantage of high speed steel accompanied with material cost increase.

45.  What is the value of having high vanadium content in the tool steel?
High vanadium will not improve the TRD performance, on the contrary material having more than 3-4% vanadium deteriorates the machine-ability and grind-ability of the tool steel.  The steels that contain 5, 10, and 15% vanadium take longer to grind and polish is low in toughness and extremely expensive.  The only benefit of these steels is wear resistance.  The TRD coating will cover 100% of the die with vanadium carbide and therefore using higher vanadium steel is of no benefit.

46. Is any cemented carbide suitable for the TRD process?
Unfortunately it isn’t. When the TRD or CVD process is used on cemented carbide a chemical compound called “W2C” is generated under the carbide layer that makes the cemented carbide brittle.  The occurrence of the W2C process and negative effect on mechanical strength would depend upon the kind of cemented carbide.  It must be selected very carefully, please contact Teikuro TRD for details.

Cemented carbide is often used with brazing in other tool steels.  The melting point of the brazing is lower than that of the TRD process (1025C/1880F), therefore the brazing material may melt during the process and the insert could fall out after the TRD process is completed.

47. Can cast metal be process with the TRD process?
When using cast metal, cast steel, or heat resistant cast alloy steel ,no void, internal cracks, or no non-metallic inclusions may exist because cracks may start from those areas during the TRD process.  This is especially true of cast tool steel because the substrate needs to be hardened at the same time.

It is important to confirm good casting conditions, sufficient cutting depth, and chemical composition were controlled when it was cast, otherwise it would have insufficient substrate hardness.

48.  How important is the substrate material selection?
It is most common to apply the TRD coating on the existing tool steel.  However this might not be the right choice for your particular application.  Finding the best material will benefit you in the long run.  If you are thinking about using the TRD process on your existing tool steel there are some things you do not have to consider.  They are wear resistance, anti-seizure, and corrosion because the TRD process improves all of these areas. 

If you want those properties on the tool steel itself you may run into other problems like poor forging, machining, cutting, heat treating properties, toughness, fatigue strength, higher costs, and market availability because of higher percentage of alloying elements are needed.  Your focus when selecting a substrate material needs to be on the above mentioned areas and not the surface areas.  Select a substrate material that will best benefit you in the end.  Please contact us for advice on the best substrate material for you application.

49.  Why and how can distortion occur?
Heating and cooling process over the substrate always occurs from the outside to the inside, therefore there is always a temperature difference, therein, the substrate will change its size according to thermal expansion phenomenon, which becomes thermal stress and cause the deformation of the substrate.  There is also always some change of micro-structure caused by the temperatures (called phase transformation) this is how the substrate is hardened.  The specific volume of crystal phase is changed with a different phase, which causes a dimensional change and the timing of the transformation between starting and ending would be different because of the temperature gap on the outside and the inside.  This can also be a cause for deformation.  It would be impossible to eliminate all distortion and deformation completely. However, it can be kept to a minimum so that the die is usable.

50.  Can distortion through the TRD process be solved?
It can be controlled through a number of different steps.  Many factors are involved in the distortion process from die design to the end prior to the TRD process. Controlling these factors will definitely produce less distortion.  If they are not controlled the distortion becomes greater.  Please contact us to discuss what factors need to be considered.

51. How well can distortion be minimized or dimension and shape be maintained?
The TRD process standard punch has been produce with a +5 um tolerance and sold with out any final machining in the past 20 years.  Teikuro has been controlling +10 um or less tolerance for punches with diameters of 50-80mm.

52.  What can be done to minimize distortion?
Select material that has a stable quality.  Specify how to cut the objects from the stock, (cut out the object vertically with larger tolerance side up).  Minimize inconsistency of heat treatment conditions.  These are some things commercial TRD treater or TRD venders can not control, but they are definitely the 1st steps in minimizing the distortion.

53.  What kind of steel has the most distortion?
If the substrate needs to be hardened, air quenching steel will minimize the distortion.  The material can be hardened at a slow quenching speed.  Steel with smaller carbide particles will also help with distortion.  A cold steel with both of these properties will produce the least amount of distortion.  Cemented carbide has been known to have the least amount of distortion since it doesn’t have any phase transformation.

54. Can the distortion be corrected after the TRD process?
Basically it can be done, but some side affects may occur.  One of the main ones is a loss of hardness.  The distortion correction between 0.01mm-0.5mm (larger pieces have more distortion) has been done at Teikuro TRD without accompanying of these problem.  Please contact us with further questions.

55. Can Teikuro TRD provide pre-coating dimensions?
Teikuro created a “state of the art” dimension control data program.  We collect all dimensions before and after the TRD process.  We are working very hard to accomplish a distortion data base by analyzing an enormous amount of data that has been collected.  By using this program we are able to provide the most reliable pre-coating dimensions to our customers. Please contact us about this information.  There is no extra charge for dimension change analysis.

Edited in 1/23/2006

• TRD Process/TD Coatings  
• Chrome Plating
• DLC-Si - Diamond Like Carbon with Silicon

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• Dimension Control

Specific application data, detailing the process and benefits of particular uses for the TRD process.

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Summary of recommended materials based on mechanical or thermal usage. 

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Teikuro’s TRD coating process can be used in virtually any industries where tooling problems occur.

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