What is TD heat treatment
Sep. 12, 2020
What is TD heat treatment
TD (Toyota Diffusion Coating Process) is a complete metal heat treatment process.
The most straightforward understanding of TD is to infiltrate wear-resistant metal atoms into the metal matrix, that is, metalizing (compared to carburizing, boronizing, and nitriding only non-metallic). The principle is to use carbon to diffuse at high temperatures. At a certain processing temperature, the metal workpiece with a certain carbon content is placed in the borax molten salt containing vanadium, niobium, titanium, chromium and other metal atoms, so that the metal atoms in the borax molten salt and the carbon atoms in the workpiece produce chemical It reacts and diffuses to form a carbonized layer on the surface of the workpiece. This process is called TD, and the carbonized layer formed is called TD layer.
The best infiltration temperature of TD metal infiltration is 920-950℃. If the material is Cr12MoV, SKD-11, in fact, this temperature is equivalent to annealing their matrix. At this time, the mold is actually in the state of eggshell-the outer shell is very hard (the hardness of the TD layer is above 3000HV), and the core is very soft (the base hardness of the metal workpiece is 35-52HRC). In the production process, in order to obtain a higher substrate hardness to support the rigidity of the surface TD layer, the workpiece must be heated to 1010-1030℃ with the furnace to re-quench and temper, so that the substrate hardness of the metal workpiece can reach 58-62HRC.
So, TD is actually a complete heat treatment process.
