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April 1-3, 2008

METALFORM
Birmingham, Alabama

Booth No. 0931

ISO 14001 Certified

TeikuroTRD is ISO certified. View our certificate online.

FAQs

Some frequently asked questions regarding TeikuroTRD process and services.

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Necessary information on substrate materials and heat treatment if customers want to have TRD coated tools with tight dimensional control

The most difficult problem in the application of TRD coating is dimensional control. Teikuro never applies TRD coating without preplanning to minimize the distortion problem. Teikuro selects the best TRD coating conditions for each application, utilizing their knowledge and experiences with distortion behavior of substrate materials.

Compared to the ordinal hardening operation of steels, TRD coating conditions are more precisely controlled to ensure minimal distortion (In fact TRD coated standard punches with + - 0.0002 inch or less have been in the market for 25 years). Teikuro's efforts never solve the distortion problem without cooperation from customers. Many factors in processing of the tools to be TRD coated (selection of materials, cut out from the materials stocks, machining, stress relieving, heat treatment, and grinding) are related to the distortion problem, as in other high temperature coating processes like as CVD.

The distortion problem can be improved, if customers understand what is distortion and what can affect the distortion. Understanding all of the distortion problem is quite difficult even for a metallurgist. This is a brief explanation, for non-metallurgist customers, what Teikuro needs from the customer to minimize the distortion problem. The items are limited to most important ones. Please contact us for more detailed information.

What is needed for tight dimensional control?
(a) Type of substrate materials used for tools to be TRD coated
(b) Hardening condition applied on tools to be TRD coated
(c) Type of surface treatment that the tools already have

Why is this important?
(a) The TRD process produces coatings of extremely hard carbides that effectively eliminate the surface damages on tools. The substrates of the TRD coated tools should be strong to prevent substrate damages under working conditions; such as plastic deformation, catastrophic failures due to poor toughness and fatigue failure etc. Thickness of the coating should also be controlled to the optimum value for each application.
Air hardening steels are usually used for the substrates of the tools to be TRD coated and each steel has the optimum heat treatment condition. Each tool should be TRD coated under the condition considering the coating thickness and the substrate requirements. Teikuro needs correct names of the tool substrate materials to be TRD coated so that Teikuro can make the best coating. For example, TRD coating on tools made of D2 under the condition for A2, will have a low substrate hardness and a thin coating. Conditions for D2 applied to S7 tools will result in thick coating and very coarse grain structure. Good performance of tools should not be expected either case.

(b) Fig.1 and 2 exemplify the effect of tempering temperature on dimensional changes and hardness in ordinal hardening of D2. For D2, two kinds of tempering temperatures are generally employed to get hardness of HRC 55 or over; low temperature of about 200 º.C ( 390 ºF) or high temperature of about 530 ºC (990 ºF). There is about 0.09 % (thickness) and 0.18 % (diameter) differences between the low temperature tempering and the high temperature tempering. This is caused by change in the crystal structures of the steels after quench-hardened followed by tempering. By application of the high temperature coating such as TRD and CVD, the substrates of the tools are repeatedly hardened, if the tools to be coated were finished to the size after hardening operation. Repeated hardening usually does not result in significant dimensional changes from the first hardening as long as the low temperature tempering and the high temperature tempering were employed both in the first hardening and the second hardening.

Surprisingly large dimensional changes (0.18 % differences means 0.0018" per 1" and 0.18 mm per 100mm) can be expected after the TRD coating, if TRD followed by the low temperature tempering applied on the tools high temperature tempered in preliminary hardening or visa versa.

The differences of dimensions by the disaccord are affected by many factors; dimension and size of tools, quality of substrate materials (scattering of chemical composition, forging ratio, microstructure, etc.), and condition of hardening and the coating ( temperature, time, cooling rate, etc.). The changes of the 00.9 % to 0.18 % shown in the Fig. 1 seem to be highest among many published data. They can be about a half of these values in some cases. However, the disaccord of tempering temperature between the pre-hardening and the coating should be eliminated, if customers want to have TRD coated tools with good dimension control. Submission of the tempering temperatures to TRD treaters from customers is critical to this process.
(c) Information on coating processes such as PVD and CVD, and the coated materials as TiN, TiC etc. is very useful in estimating the heat treatment condition applied to the tools and determining the treating condition for minimized distortion problem. For example, PVD for tool coating and nitriding are usually accompanied with the high temperature tempering effect on the substrates. CVD can be done with the low temperature tempering and the high temperature tempering.

Within sections (a) to ( c ),
(b) is most important for only D2. It is because other steels generally used for TRD coating, are usually tempered at the low temperature (A2 and S7) or at the high temperature (DC53 and High speed steels)
(a) is highly desirable for all kinds of steels. It is especially important, in case the tools are made of Cruwear and CPM since these can be hardened at very wide ranges of hardening temperatures.
(c) is more desirable for TRD (TD) coating and CVD coating applied on D2 tools for the same reason as (a).