热喷涂金属陶瓷涂层是改善不锈钢(SS)水轮机的气蚀和耐磨性的适当解决方案,尤其是在含沙量高的河流中,比如巴西的马德拉河。然而,一些金属陶瓷容易溶解在河水中,导致涂层过早失效和昂贵的维护。此外,通过将金属陶瓷耦合到SS引起的电化学腐蚀可以加速涂层溶解。因此,六种金属陶瓷的耐腐蚀性能(WC-12Co,WC-10Ni,WC-10Co-4Cr,Cr3C2-25NiCr,在模拟马德拉河水的溶液中评估了Cr3C2-10NiCr和Cr3C2-10Ni)以及这些材料与CA6NMSS耦合的电化学耐腐蚀性。WC-12Co和WC-10Ni金属陶瓷表现出最高的腐蚀速率,0.077和0.068毫米/年,分别,而WC-10Co-4Cr(0.017毫米/年)和Cr3C2基涂层(0.005至0.007毫米/年)中的Cr含量导致它们以较慢的速度腐蚀。此外,WC-10Co-4Cr和Cr3C2基金属陶瓷在与CA6NMSS耦合时表现出可忽略的电化学腐蚀电流,使它们成为覆盖水轮机的好选择。相比之下,WC-12Co和WC-10Ni涂层经历了更严重的电化学腐蚀过程,这将大大减少这些材料作为水轮机涂层的寿命。
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, Cr3C2-25NiCr, Cr3C2-10NiCr and Cr3C2-10Ni) 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 Cr3C2-based coatings (0.005 to 0.007 mm/year) led them to corrode at slower rates. Moreover, the WC-10Co-4Cr and Cr3C2-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.