Ceramic Coatings
Development of a new coating
The development of a new coating starts with an extensive literature search. Based on the gained knowledge a test programme will be set up. If a new substrate material is used, first tests will be conducted to find out whether the substrate material properties will change due to the coating process, e.g. some metals can become brittle due to hydrogen at elevated temperatures.
The (unwanted) influence of the coating (process) on the mechanical behaviour of the substrate material can be established using the strain test. A thin coated wire is subjected to a strain test. If there is no difference in fracture surface and strain diagram between the uncoated an coated wire, the coating (process) has no influence on the mechanical properties. (see Figure 7 and 8).
Fig 7: Example of a ductile fracture surface. The coating (process) has not influenced the mechanical properties of the wire.
Fig 8: Same substrate material but now with a brittle fracture surface. The coating (process) has influenced the mechanical properties of the wire.
In case there is an influence, test can be carried out to determine the exact cause. If the cause is known, usually a solution can be found to prevent the change in properties.
Other properties, like stability at high temperatures, thermoshock resistance, optical transmission corrosion resistance etc., can also be determined. The test results help optimising the coating process for different applications.