Luiz Leonardo Augusto, de Andrade Juliano, Pesqueira Camila Melo, Siqueira Irene Bida de Araújo Fernandes, Sucharski Gustavo Bavaresco, de Sousa Milton Jakson
Mechanical Systems Department - Lactec Institute, Curitiba, Brazil.
Materials Department - Lactec Institute, Curitiba, Brazil.
J Therm Spray Technol. 2021;30(1-2):205-221. doi: 10.1007/s11666-021-01152-8. Epub 2021 Jan 21.
Thermally sprayed cermet coatings are adequate solutions to improve cavitation and wear resistance of hydraulic turbines made of stainless steel (SS), especially in rivers with a high sediment load, such as the Madeira River in Brazil. However, some cermets are easily dissolved in river water, leading to premature failure of the coating and costly maintenance. Moreover, galvanic corrosion induced by coupling the cermet to a SS can accelerate the coating dissolution. Therefore, the corrosion resistance of six cermets (WC-12Co, WC-10Ni, WC-10Co-4Cr, CrC-25NiCr, CrC-10NiCr and CrC-10Ni) and the galvanic corrosion resistance of these materials coupled to CA6NM SS were evaluated in a solution that simulated Madeira River water. WC-12Co and WC-10Ni cermets exhibited the highest corrosion rates, 0.077 and 0.068 mm/year, respectively, whereas the Cr content in the WC-10Co-4Cr (0.017 mm/year) and CrC-based coatings (0.005 to 0.007 mm/year) led them to corrode at slower rates. Moreover, the WC-10Co-4Cr and CrC-based cermets exhibited negligible galvanic corrosion current when coupled to the CA6NM SS, making them good options to coat hydraulic turbines. In contrast, WC-12Co and WC-10Ni coatings underwent a more severe galvanic corrosion process, which would drastically reduce the lifespan of these materials as hydraulic turbine coatings.
热喷涂金属陶瓷涂层是提高不锈钢（SS）制成的水轮机抗气蚀和耐磨性能的合适解决方案，特别是在泥沙含量高的河流中，如巴西的马德拉河。然而，一些金属陶瓷易溶于河水，导致涂层过早失效和维护成本高昂。此外，金属陶瓷与不锈钢耦合引起的电偶腐蚀会加速涂层溶解。因此，在模拟马德拉河水的溶液中评估了六种金属陶瓷（WC-12Co、WC-10Ni、WC-10Co-4Cr、CrC-25NiCr、CrC-10NiCr和CrC-10Ni）的耐腐蚀性以及这些材料与CA6NM不锈钢耦合后的电偶耐腐蚀性。WC-12Co和WC-10Ni金属陶瓷的腐蚀速率最高，分别为0.077和0.068毫米/年，而WC-10Co-4Cr（0.017毫米/年）和CrC基涂层（0.005至0.007毫米/年）中的Cr含量使其腐蚀速率较慢。此外，WC-10Co-4Cr和CrC基金属陶瓷与CA6NM不锈钢耦合时表现出可忽略不计的电偶腐蚀电流，使其成为水轮机涂层的良好选择。相比之下，WC-12Co和WC-10Ni涂层经历了更严重的电偶腐蚀过程，这将大大缩短这些材料作为水轮机涂层的使用寿命。
