TD Surface Treatment
The Toyota Diffusion (TD) Process was initially developed by the Toyota Central Research and Development Laboratories to facilitate a surface treatment that created a hard & wear resistant surface for large automotive press tools.
The TD (vanadium carbide) surface treatment process is a member of the “case” hardening family of processes, the most common being nitriding and carburising - where reactive elemental species are diffused into the steel matrix. The subsequent case that is formed is hard and wear resistant, where the specific chemical and mechanical properties achieved are attributable to the individual elements that are diffused, time & temperatures involved. The superior mechanical & chemical properties of TD surface treatments are discussed over.
Applications
Given the superior wear resistance, high seizure resistance and reduced lubricant requirement that is associated with TD surface treatments, they have historically been used by the automotive industry in specialised press tool applications such as tight radiuses and deep draws. More recently, however, with the increased use of high strength steels, larger volumes and throughput requirements, automotive companies have been evaluating the use of TD surface treatments more widely on other areas of press tools.
TD surface treatments are not, however, restricted to automotive press tools, they can be applied to a range of engineering components, including: shafts, screws, bushes, blades, taps, pins and plugs. For the best results, cold work tool steels (typicaly D2) are required - the high chromium content assists in the formation of chromium and other carbides. TD surface treatments can also be applied to other materials such as hot work (H13 and H11) and high speed (M2, M41 and powder metallurgry) tool steels.
Surface Hardness Comparison
The superior surface hardness of TD surface treatments is demonstrated in Figure 1, and compared against competing processes. The formation of vanadium (V), niobium (Nb), and chromium carbides in the steel matrix explains the superior surface hardness possible with TD surface treatments. The carbide layer and additional diffusion layers formed during TD surface treatment are further supported by the subsequent hardening and double tempering of the tool steel, resulting in the optimal combination of wear resistance and toughness.
Peel Strength Comparison
TD surface treatments is a diffusion process, not a coating, the active elements diffuse into the steel forming strong metallurgical bonds in the steel matrix.
Hence the superior peel strength of TD surface treatments when compared to coatings such as the hard chrome & PVD processes as demonstrated in Figure 2.
Other Services
HCE offer a range of material enhancement and surface engineering services, including, hard chrome plating, electroless and electrolytic nickel, SermeTel® coatings, vacuum heat treatment, Nitreg® nitriding, grinding, turning, texturing and superfinishing. HCE employ a number of experienced and qualified metallurgists and are supported by a fully equipped metallographic laboratory and state-of-the-art mircohardness testing equipment.
- Extremely High Hardness
- Impact Resistant
- High Wear Resistance
- High Seizure Resistance
- Superior Peel Strength
- Diffusion Process
- Harder than TiN & TiCN Coatings
- Massive Tool Life Increases
- Reduced Lubricant Requirements
- Increased Throughput
