In cold working applications cold welding of work material to tool steel is almost completely eliminated. The carbide layer between the tool and work material reduces the tool surfaces’ chemical affinity for cold welding to occur. This means an end to galling, scoring, pick-up and seizure. This increase in part quality is immediately visible.
The properties of the TD coating impart substantial improvement to all wear related applications, e.g. stamping dies, forming dies, forging dies, pipe, tube and wire manufacturing, roll forming..
Hot Working Applications:
TD coating has also shown success in hot working applications, namely high pressure die casting (both aluminium and zinc) as well as hot forging.
Die casting: used mainly on casting cores and inserts, the TD provides a dense, well bonded barrier between the casting shot and the tool steel surface. The coating does not flake or delaminate and resists the thermal cycling stresses. The high density of the VC layer prevents the corrosive molten metal from binding with iron in the tool and this factor reduces adhesion dramatically.
The VC layer also has low affinity for molten aluminium and zinc. This prevents welding of the melt material to the tool steel. Also the high hardness of the coating prevents deterioration of the surface through multiple ejection cycles and any re-polishing that is performed from time to time.
Another major advantage when TD is applied to a pre-polished cavity for example is that the surface quality of the as cast components is preserved for a much longer period of time , reducing the need to post polish castings and eliminating the need to re-polish the cavity.
Hot forging applications are very demanding on the tooling surface. Hot forging involves high heat, large amounts of force, together with high abrasion and adhesion. TD helps to resist these actions and extend tool life in hot forging punches and dies. One unique advantage TD has is that it actually forms its own solid lubricant if it is oxidised on the surface. VC is oxidation resistant up to 550°C and as long as the tool surface remains below this temperature oxidation occurs very slowly.
A schematic of Vanadium pentoxide monolayer
Dependence of an increase in weight of the vanadium carbide coating upon the temperature in oxidation in air (heating rate – 10°C/min)
If you wish to compare the differences between TD Coating and PVD coating please click here
Typical TD Applications
Press dies, forming dies, deep drawing dies, bending dies, extrusion dies, swaging, crimping, pierce and notch punches, extrusion punches, bolt forming tooling, hex trim punches, blanking tools, shear blades, cropping dies, slitters, cut-off blades, wood chipper knives, mandrels, non-return valves, drill bushes, collets, casting core pins and inserts, traveller rings, rollers, locating pins, cam plates, high pressure pump pistons etc.