Influence of Laser Treatment on the Corrosion Resistance of Cr3C2-25(Ni20Cr) Cermet Coating

The influence of the laser treatment on the corrosion resistance of the Cr3C2-25(Ni20Cr) cermet coating on the Al7075 (EN, AW-7075) substrate (Cr3C2-25(Ni20Cr)/Al7075) was investigated. The coating was produced by the cold sprayed (CS) method. The tested coatings were irradiated with a laser spot speed of 600 mm/min, 800 mm/min, and 1000 mm/min. The mechanical properties of the Cr3C2-25(Ni20Cr)/Al7075 were characterized by microhardness (HV) measurements. The surface and microstructure of the specimens were observed by ascanning electron microscope (SEM) and other assistive techniques. The corrosion test of materials wascarried out by using the electrochemical method in the acidic chloride solution. Cermet coatings perfectly protect the Al7075 substrate against contact with an aggressive corrosion environment. The laser remelting process of the Cr3C2-25(Ni20Cr) layer caused the homogenization of the structure cermet coatings. The irradiation with the laser beam eliminates microcracks and pores on the Cr3C2-25(Ni20Cr) surface. However, the best effect of improving the anti-corrosion properties of cermet coating was obtained for the lowest laser spot speed (i.e., 600 mm/min). It was found that the corrosion rate of the Cr3C2-25(Ni20Cr) cermet coating was reduced by more than two times compared to the highest speed of the laser spot.

Corrosion Behavior of Inconel 625 Coating Produced by Laser Cladding

Anti-corrosion properties of Inconel 625 (In) laser cladding coatings onto the (S235JR) steel (S) were investigated. The coatings were produced with the use of wire (WIn/S) or powder (PIn/S). The mechanical properties of the Inconel 625 coatings were characterized by microhardness measurements. The PIn/S shows the highest hardness. The surface and microstructure of the specimens were observed by a scanning electron microscope (SEM). The surface analysis of the laser cladding coatings by energy-dispersive spectroscope (EDS) indicated that the structure of the WIn, and PIn coatings depend on its production technique. The microstructure of the WIn and PIn coatings have a dendritic columnar character. Corrosion test materials were carried out by using electrochemical methods. The corrosive environment was acidic chloride solution. It turned out that the PIn/S coating, which was produced by laser cladding method with the use of Inconel 625 powder, has the best anti-corrosion properties in an aggressive chloride environment.

Influence of Heat Treatment on the Corrosion Resistance of Aluminum-Copper Coating

Influence of heat treatment on the corrosion resistance of the aluminum-copper (Al-Cu) coating on the aluminum substrate was investigated. The coating was produced by the electrical discharge alloying (EDA) method. The surface and microstructure of the specimens were observed by a scanning electron microscope (SEM). The phase analysis of the composite materials by X-ray diffraction (XRD) and energy-dispersive spectroscopy (EDS) indicated that intermetallic compounds (i.e., CuAl2 and Cu9Al4) were formed through reactions between Al and Cu. during the EDA process. A significant increase in the hardness of the Al-Cu coating was affected by the improvement of the alloy structure. The heat treatment of materials was carried out at 400 °C or 600 °C in the air atmosphere. A corrosion test of materials was carried out by using electrochemical methods. The corrosive environment was acidic chloride solution. After heat treatment at 400 °C the mechanical properties of the Al/Cu alloy increased significantly and the oxide layer protect of the alloy surface against corrosion. However, after heat treatment at elevated temperature, i.e., 600 °C it was found that the (Al2O3)ads and (CuO)ads coatings were destroyed. The mechanical properties of the Al/Cu alloy decreased, and its surface has undergone deep electrochemical corrosion.