Piston rings
In tribometer experiments CVD-diamond coated silicon carbide piston rings allow dry runs up to 100 km. The diamond wear in these experiments is below 3 µm. Using adjusted process parameters, a textured diamond layer in the direction can be created on the piston ring surface. Therefore, the surface is the most wear resistant when exposed to friction. The diamond coating of piston rings, which has been under investigation since 1995, is now used in industry.
DiaCCon, a company founded by the chair of WTM, is the leading research entity for this application worldwide. A new research topic is the expansion of the diamond piston ring applications to metallic ring materials such as steel or hard metals.
Diamond electrodes
The durability of diamond titanium electrodes is limited especially due to the anodic load of the electrochemical dissociation of the titanium carbide interface between diamond and titanium substrate. With the use of tantalum or niobium as more stable electrode material, the lifetime of diamond electrodes can be increased significantly. A new research effort aims to develop economic diamond electrodes, for which firstly a tantalum or titanium intermediate layer is deposited on titanium or steel plates. After this, the boron doped diamond coating will be deposited.
Steel tools
For Aluminium high pressure die casting, different diamond coated steel tools with TiNB-intermediated layers are applied at industrial partners. The lifetime of bending tools can be increased from a few weeks to several months.
Diamond coated steel sonotrodes for the ultrasonic welding of Aluminium cables are currently also being tested by industrial partners.
The CVD diamond layer can permanently inhibit the reaction of the tool surface with liquid or solid Aluminium. The necessary strength of the steel must be adjusted after every heat treatment, which is steel specific, to avoid material failure due to insufficient fatigue strength. The CVD diamond coating of Tungsten tools is being researched as an alternative or as an addition to the high temperature intermediate layer to avoid special heat treatments.