Method for characterizing a coating

1 . A method for assessing quality of a thermally sprayed run-in lining coating on a housing of a turbomachine, comprising the steps of:

providing a housing component having a surface;

measuring a mass and optically measuring a volume of the housing component using a projector and two cameras in a three dimensional structured-light projection measurement system;

prior to optically measuring, treating the surface of the housing component to reduce reflections by spraying chalk on the surface, applying titanium dioxide to the surface, matting of the surface by vibratory grinding or matting by tumbling;

thereafter, thermally spraying a run-in coating on the housing component; the run-in coating having a surface roughness with roughness peaks;

defining a density of the run-in coating from layer parameters in advance;

thereafter, measuring a mass and optically measuring a volume of the same housing component with the applied run-in coating thereon;

thereafter, determining a difference in the mass and volume before and after coating of the housing component,

thereafter, determining a density of the run-in coating from the difference in the mass and volume before and after coating of the housing component;

detecting damage or monitoring quality of the run-in coating by way of a deviation from the density defined in advance;

wherein the housing component is securely held in a holder before and after the coating;

monitoring quality of the run-in coating from the deviation of the density thereof before and after coating of the housing component;

automatically recording data of the layer parameters;

evaluating the recorded data within a framework of a statistical process control;

wherein the surface roughness of the coating is smoothed by software post-processing to fill in valleys between the roughness peaks so it can be compared to a mechanical measurement of the coating;

mechanically measuring the housing component with calipers applied only to the roughness peaks of the surface of the housing component; and

comparing the software post-processing with the mechanical measuring of the housing component with calipers.

2 . The method according to claim 1 , wherein, during the optical measurement of the volume, the surface roughness of the coating is optically measured at the same time.

3 . The method according to claim 1 , wherein the coating has a layer thickness of at least 0.05 mm and a maximum of 5 mm.

4 . The method according to claim 1 , wherein, the run-in coating is treated to reduce reflections before measuring the mass and optically measuring the coated housing component.

5 . The method according to claim 1 , further comprising the steps of:

providing a basic body that is different than the housing component;

thermally spraying a run-in coating on the basic body in parallel with the housing component;

determining a density of the run-in coating on the basic body and the run-in coating on the housing component in the same way.

6 . The method according to claim 5 , further comprising the step of:

heat treating the run-in coating on the housing component and heat treating the run-in coating on the basic body after the step of determining the difference in the mass and volume of the run-in coating of the housing component and basic body before and after coating.

7 . The method according to claim 1 , further comprising the steps of:

providing a holder for arranging the housing component;

optically measuring the volume of the housing component arranged in the holder;

weighing a mass of the housing component arranged in the holder.