Manufacturing of Thick, Crack-Free Wear Protective Coatings on Complex Geometries for Gas Turbine Parts

Thermal sprayed wear protective coatings in gas turbines are applied on mechanical highly stressed part surfaces to protect the substrate from abrasion during the machine start up and operation. The high temperature resistant coating sprayed with a high velocity oxy-fuel (HVOF) process on complex geometries of part surfaces consists of a chromium-carbide / nickel-chromium material. The required high coating thickness is connected with a high risk of crackformation within the coating. To understand the influence of specific coating parameters like robot velocity, spray distance and part cooling, metallographic investigations are conducted. In addition following analytical methods are also utilized: Element mapping, In-situ coating property (ICP)-Sensor, X-ray diffraction (XRD). These information is used to adjust other important coating characteristics such as porosity,hardness and mechanical stresses and allow the manufacturing of thick, crack-free wear protective coatings, thus enhancing the application area in gas turbine products.