Answers to Typical Questions
about TD Coatings

What exactly is TD coating?

TD (Thermal Diffusion) coating is a coating process that diffuses a layer of carbides onto and into the surface of the tooling. The TD layer is metallurgically bonded to the tooling providing superior adhesion strength, which can drastically extend the life of your tooling. The adhesion strength coupled with a coating hardness of 3500+ Vickers (90+ Rockwell C-Scale) is ideally suited for manufacturing industries. TD Center has seen outstanding results on severe applications where other coatings such as PVD (TiN, CrN) and CVD (TiC) have failed.

Does TD really work?

Every application is different, and some applications are better candidates for the TD process than others. Call us with your situation and we will give you an honest evaluation of what you can expect. Click here for a link that details some of our customers' success stories.

Why use TD versus PVD or CVD?

Think about it, every time you have to send a part out for coating, you have to schedule downtime, run up enough parts, tear down the die, pack the blocks, ship it, wait for it, receive it back in, build the die back up, set up the die in the machine, run enough parts to get the process back into spec and hope the coating works! That's a huge expense and inconvenience, let alone production riding you when the schedule changes, all to get a coating that won't last more than a couple of months.

So why settle for a PVD or CVD coating? If you use TD coating, you won't have the headaches and the hassle. Our TD coating can outlast other coatings 3-4 times. You will see payback the first time you don't send your die out to be coated.

Comparison of our TD coating versus PVD or CVD:

• High temperature process diffuses coating onto and into the surface of the substrate for better adhesion - greater durability, higher peel strength, and longer life
• Vanadium carbide has superior hardness - greater durability, reduces friction, and longer life
• Extend the life of your tooling 8, 10, 12 times or more
• New and used tool contamination (grease, paint, grinding wheel material, rust previous coating) has minimal affect on the TD coating process, unlike PVD
• The TD Center provides full-coverage of your product --- not line-of-sight coating method like PVD
• Better payback when all costs are considered
• Our TD process outlasts PVD/CVD by 3-4 times

What are the benefits of TD Coating?

• Reduce tooling cost by extending the life of tooling by 5 to 12 times and potentially eliminate spare details
• Decrease maintenance time and expense - Reduce or eliminate galling
• Reduce or eliminate lubricant expense and problems - Cost, removal, storage and handling, clean-up, and governmental regulations
• Increase press up-time
• Improve part quality and surface finishes - TD coating can allow you to significantly increase production rates
• Improved work environment
• Low coefficient of friction reduces adhesive wear
• Parts are formed with less force and release more easily

What are the applications for TD Coating?

There are many potential applications, including tooling and component parts. These are some of the applications in the metal-forming industry:

.	Stainless Steel forming	.	Tube forming and bending	.	Extrusion
.	Deep draw dies	.	Form blocks	.	Curling
.	Flange dies	.	Swaging	.	Flaring
.	Ironing	.	Sizing	.	Piercing tools
.	Cold and hot forging	.	Roll forming	.	Die-casting
.	Stab blades	.	Fine blanking	.	Shearing
.	Rollers	.	Expanding punches	.	Mandrels
.	Hydro-forming tooling	.	Any other tooling which exhibits wear, galling or sticking

What are the benefits of TD Center's customer service?

From our customer service, to our sales people who are tool and die experts, to our in-house metallurgist, the TD Center are the Thermal Diffusion coating experts. In 1988, we pioneered TD Coatings in North America. We have over 112 years of combined experience doing nothing but TD coatings, more than all our competitors combined.

• Best delivery with quicker turnaround times - 3-4 days for non-post hardened and 5-6 days for post-hardened (includes weekends)
• Quality leader - Dimensionally stable results with state-of-the-art materials lab and staff metallurgist; ISO9001:2000 certification
• More delivery options - FedEx, UPS, Ground, Air, or door-to-door gets it there when you want it
• More payment options - We now take Visa, MasterCard and American Express
• Ability to check your order status on-line
• Open 24 hours per day, 6 days per week

What is the procedure for setting up a new account with the TD Center?

We do a Dunn and Bradstreet credit check on all new customers prior to processing their order. To avoid delays on your order, please call us in advance to start this process.

If your credit check passes our approval, we immediately enter your company in our system and start processing your order. No order ships without a purchase order number.

If your company has a D&B credit rating of a 4 (poor) or 3 (fair) with a downward trend, your company is automatically put on payment-in-advance. We cannot begin processing your order until we receive your payment. We accept payment-in-advance via check, wire transfer, and credit card (Visa, MasterCard, American Express).

If you do not have a credit rating with D&B, then we require you to fill out a credit application form. We require credit references from your bank and other suppliers to determine what level of credit, if any, that we can extend. We encourage you to take these steps prior to your first order since this process takes time.

What are the payment options?

For customers that meet our credit requirements, we extend credit terms as Net 25th Prox. This means that any invoice during a given month requires payment by the 25th of the following month. For example, an invoice dated 1/01/04 thru 1/31/04 is due by 2/25/04.

For all other customers, we accept credit cards (MasterCard, Visa, and American Express), wire transfer or checks.

What is the TD Center’s shipping address?

TD Center
835 South Marr Road                                              Columbus, IN 47201

Phone: 812-379-4243

 

What is the preferred method of shipping parts to the TD Center?

For smaller orders, our preferred method of receiving shipments is by UPS. We do receive shipments from FedEx, Airborne, Emery Worldwide, DHL, etc.

For larger shipments, we can receive your order via your normal trucking company.

For expedited, door-to-door service, we offer pick-up and delivery in Indiana and surrounding states. Call for details.

Why is a Quote / Process form required?

A few reasons:

• Suitability - We need to verify that the tool can be TD coated
• Size movement - As the TD process is performed at high temperatures, some size movement can occur in the steel due to possible different microstructures present. This is directly related to the type of steel and its previous heat treatment. If we know this information, we predict and correct/minimize the effects.
• Heat treatment and manufacturing application - To verify that the intended heat treatment correlates well with the intended application and the TD coating
• Material worked and volume produced - this tells us whether we should improve on the base metal properties to improve the support for the TD coating.

Where can I get a Quote / Process form?

From our literature page and you can click here to get the Quote / Process form.

Do I have to fill out a process sheet to get work done?

No. If you prefer you can call or fax in the details. The completed process sheet does speed up the operation. Required information includes steel type, special processing instructions, a purchase order, and a ship to address.

What about shipping and packaging?

TD coated tools received or shipped are ready-to-use. When sending, pack sufficiently with corrugated cardboard to avoid transport damage. Plastic bubble wrap will still allow damage to occur. Parts sent in a "soft" state should be packed with extra care to avoid shipping damage.

How long will it take?

Because of the high temperatures of the TD process, and pre and post surface preparation, average turn-around time is typically 3-4 days for the TD process. Post hardening and extensive polishing can add 1 to 2 days. These lead-times do include weekends.

What if I need my parts back quicker?

Please make those needs known as you talk to us or fill out the process sheet. Depending on the existing work load at the time, we will attempt to accommodate your needs.

How thick is the coating?

Similar to other thin film coating methods, about .0002-.0003" thick.

How hard is the TD coating?

Actually a coating cannot be measured accurately with a Rockwell 'C' test, and the Rockwell C scale does not extend past 68. Another issue is that the diamond plunge test will not record the contribution of a .0002-3" thick layer on the surface. Thin film coatings like our TD are measured on a Vickers scale from 0-6000. For example, hardened tool steel measures 500-800 (55-65Rc); Chrome is 600-900 (60-66Rc); TiN is 2200-2500 and Vanadium Carbide (VC) or TD is 3500-3800. Our newest product, Nova3 is 3800-4400 on the Vickers scale. If you use a calculation to compare Vickers to Rockwell C, VC is 85-90 Rockwell C, so Nova3 would be greater than 90Rc.

What if the part has been previously coated?

The TD Center can remove PVD and CVD coatings. Chrome on the surfaces will have to be removed by reverse electrolysis. Previously nitrided surfaces are more an issue and the application should be discussed with the TD Center.

You said TD is a hot coating, how hot?

The coating is diffused in a solution of molten salt at the austenitizing temperature of tool steel, 1750 to 1850°F. Only when steel is in an austenite stage is carbon available for the Vanadium Carbide to form. Applying the coating at this temperature actually diffuses the coating into the surface of the substrate. This molecular bond is what makes the TD coating so durable.

Can I send in steel that hasn't been heat-treated?

Yes. The TD process will also heat-treat the tool steel. Standard RC of TD processed A, D, CPM, and M series steels will be in the 55-58RC range, while H-series steels will be in the 49-54RC range. However, "soft" or annealed steels do not result in as good surface finishing as steels that have been hardened. And the potential for dimensional movement is greater on a detail that has not been hardened before the TD process. Additional vacuum heat treatment can elevate the RC of the substrate after TD processing if full hardness is required.

Will the TD process make the steel too hard?

While the hardness of the TD coating exceeds Rockwell limits (over 90 RC), the hardness of the substrate is not affected by the coating. The coating is around .0003 inches thick (depending on the tool steel type), which does not change the ductility of the tool itself. Substrate selection and tempering will determine the overall hardness of the tool.

Will the TD process change the size of my parts?

The precise movement of tool steel in a heat treat process is difficult to determine. However, the TD process is similar to a heat treat cycle, so some dimensional change may occur. We minimize distortion by using a special quench cycle and we minimize size movement by applying specific tempers.

For jobs with extremely tight tolerances, or if you would like a machining recommendation, please contact us prior to final sizing of tooling. Leaving grind stock on non-working areas can facilitate final sizing after the process. Contact us for machining recommendations on various tool steels.

Providing us the information specified in our process sheet (how the part was heat treated, what dimensions are critical, providing us a print), helps us control the size movement in your parts.

Will it anneal my tool?

No, but it will affect the hardness. The TD process is a heat treat process. Air hardened tool steels will come out of the process hardened. The type of steel, if and how they were heat treated previously and the size and shape of the tool will determine exactly how hard the substrate will be after TD. We offer an option called Post Hardening for people who would like to increase the hardness after coating.

What is Post Hardening?

In some cases, where heavy forming forces are present, or difficult to form material are worked (e.g. stainless steels), TD treated cold work tool steels are re-hardened i.e. post TD hardened, in a vacuum furnace. This does increase the substrate hardness by 1 or 2 Rockwell points and provides better support for the coating. High speed steels in most cases require post hardening to obtain maximum working hardness (61-64 HRC).

What kind of steel can be treated with the TD process?

Any air hardened tool steel that contains at least .3% carbon content. Most H, D, M, A, and CPM series tool steels fall into this category. The process also works well on carbide (10% binder or higher) and some grades of martensitic stainless steel. It does not work with Anvilloy, TZM, Bronze or any steel that has been nitrided. (We can remove the nitrided layer if necessary).

Does the grade of steel used make a difference?

Yes. Premium grade steels are highly recommended for the TD process. Inferior grades have many impurities that can impede proper finishing and processing.

Is tool maintenance different with an TD coated part?

One of the many benefits of TD coating is a reduction in tool maintenance. You should notice a decreased need for grinding / polishing.

In the event that galling does build up on the TD layer, do not use conventional hard fiber/carborundum/diamond media to remove! We recommend non-aggressive abrasives such as scotch-brite type discs, aluminum oxide papers (300-600 grit), or chemical removal of any build-up. This will protect the TD layer from damage and in many cases, allow the detail to be re-used.

How do you charge for coating parts?

We charge by weight, with a tiered scale depending on the overall size of the order. The more you send in, the cheaper it will be.

How large a part can I treat?

The part should fit within a cylinder 22" in diameter and 22" deep. Call on slightly larger parts.

What surface finish is required prior to TD coating?

The goal is to polish the working surfaces to a mirror finish of 5-8 RMS. Polishing is actually a very critical step that ensures the best possible performance of our coating. A highly polished surface will reduce friction and improve material flow.

Less friction is one of the keys to:

• reducing or eliminating lubrication
• reduction or elimination of galling
• better part appearance
• reduction in maintenance

In addition, a highly polished surface provides better adhesion of our coating to your tool. If machine lines are not polished out, you essentially have a very hard file after you add our coating.

There are several techniques to keep in mind when polishing. Please refer to our technical bulletin that covers some tips on polishing.

Do you polish tooling?

Yes, we have a staff of over 10 people that are professional polishers. We provide basic polishing, buffing with diamond compound and light touch-up as part of our coating services. If you require additional polishing services, we charge by the hour. We use mold stones (320, 600, 900 and 1200 grit) after the major surface damage has been removed, then 3µm diamond paste. Final stoning should be in the direction of work material flow.

Can the TD process be applied more than once?

Yes. The TD process may be re-applied several times, perhaps 4-6 times, or more, depending on the tool steel and the application. Contact us for more information.

TD Center
835 South Marr Road, Columbus, IN 47201
Ph: 812-379-4243 • Fax: 812-379-4222