Salt Spray Corrosion Resistance of NiCoCrAlY Coatings after Heat Treatment

The 500h neutral salt spray resistance of LPPS (Low Pressure Plasma Spray) NiCoCrAlY coating on low expansion superalloy GH907 was investigated and compared with that of LPPS NiCr coating by means of SEM,EDS etc.The results of SEM showed that the NiCoCrAlY coating had few corrosion pits,and remained to be integral and smooth.EDS analysis showed that the corrosion products were Al oxide.The corrosion level was slightly reduced to the 9th.A few corrosion spots were observed,the integrity and uniformity of the NiCr coating were damaged and some cracks appeared in the NiCr coating after testing for 500 h,and the corrosion level was 4th.The corrosion products were mainly composed of oxides of Ni,Fe,Co,etc.The NiCoCrAlY coating exhibited better neutral salt spray corrosion resistance than NiCr coating.