Thermal sprayed zirconium coatings for corrosion resistance
Vacuum Plasma Spraying (VPS) is conducted in inert reduced pressures. This results in higher particle velocities than in atmospheric plasma spraying. Reverse arc sputter cleaning and pre-heating of the workpiece lead to elevated substrate temperatures during deposition, allowing sintering of the coating and, thus, enhanced densities and bond strengths. Inert Environment Electric Arc Spraying (IEAS) is performed in inert gas chambers, utilizing wire as the feedstock. This leads to lower gas content in the coating, since the initial gas content in wire is lower than that of the powder feedstock used in VPS. Controlled atmosphere sprayed zirconium coatings had inferior mechanical and corrosion properties when compared with bulk zirconium. The VPS coatings displayed higher bond strengths and better cavitation erosion resistance than did the IEAS coatings. The IEAS coatings had lower gas content and showed better electrochemical and corrosion behavior. The lower gas content for IEAS was due to a lower initial gas level in the wire feedstock used in this process. Also, scanning electron microscopy revealed that larger particles result in the IEAS process. Thus, a smaller surface-area-to-volume ratio is available for gas-metal reactions to occur. Improvements in mechanical and corrosion properties for the IEAS coatings were due to elevated substrate temperatures during deposition. Compressive surface stresses induced by post-spray shot-peening enhanced corrosion and cavitation resistance of IEAS coatings. Coating porosity caused failure during immersion testing. Therefore, it was concluded that controlled environment thermal spraying of zirconium is not suitable for forming corrosion resistant coatings on steel. ZrN coatings were formed by electric arc spraying using a nitrogen shroud and post-spray nitriding. Two phases; ZrN and zirconium solid solution, exist in the as-sprayed coating. Nitriding increases the proportion of ZrN.
- Research Organization:
- USDOE Assistant Secretary for Conservation and Solar Energy, Washington, DC (United States). Consumer Products Div.
- OSTI ID:
- 5857502
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
Similar Records
The Effect of Oxygen Contamination on the Amorphous Structure of Thermally Sprayed Coatings of Cu47Ti33Zr11Ni8Si1
Effect of post treatments on the corrosion resistance of plasma sprayed duplex stainless steel coating in salt water
Related Subjects
STEELS
CORROSION RESISTANCE
SURFACE COATING
ZIRCONIUM
SPRAYED COATINGS
CAVITATION
DEPOSITION
HARDNESS
MECHANICAL PROPERTIES
POROSITY
SHOT PEENING
SINTERING
STRESSES
WEAR RESISTANCE
ALLOYS
COATINGS
COLD WORKING
ELEMENTS
FABRICATION
IRON ALLOYS
IRON BASE ALLOYS
MATERIALS WORKING
METALS
SURFACE TREATMENTS
TRANSITION ELEMENTS
360105* - Metals & Alloys- Corrosion & Erosion