Exceptionally high cavitation erosion and corrosion resistance of a high entropy alloy

Abstract

Cavitation erosion and corrosion of structural materials are serious concerns for marine and offshore industries. Durability and performance of marine components are severely impaired due to degradation from erosion and corrosion. Utilization of advanced structural materials can play a vital role in limiting such degradation. High entropy alloys (HEAs) are a relatively new class of advanced structural materials with exceptional properties. In the present work, we report on the cavitation erosion behavior of AlCoCrFeNi HEA in two different media: distilled water with and without 3.5wt% NaCl. For comparison, conventionally used stainless steel SS316L was also evaluated in identical test conditions. Despite lower hardness and yield strength, the HEA showed significantly longer incubation period and lower erosion-corrosion rate (nearly 1/4th) compared to SS316L steel. Enhanced erosion resistance of HEA was attributed to its high work-hardening behavior and stable passivation film on the surface. The AlCoCrFeNi HEA showed lower corrosion current density, high pitting resistance and protection potential compared to SS316L steel. Further, HEA showed no evidence of intergranular corrosion likely due to the absence of secondary precipitates. Although, the degradation mechanisms (formation of pits and fatigue cracks) were similar for both the materials, the damage severity was found to be much higher for SS316L steel compared to HEA.

High-Temperature Nano-Indentation Creep Behavior of Multi-Principal Element Alloys under Static and Dynamic Loads

“…MPEAs are composed of several elements in equiatomic or near-equiatomic proportion and despite complex chemistry, they usually form a simple single-or multi-phase solid solution [1][2][3]. The presence of different sized atoms in the unit cell leads to high degree of lattice strain in MPEAs [1] and results in high hardness and strength, good fracture toughness at cryogenic and elevated temperatures, high fatigue resistance, good wear, erosion and corrosion resistance [3][4][5][6][7]. Local lattice distortion, nano-clustering, and inhomogeneity at microstructural length scale in MPEAs [8] may significantly affect their mechanical properties including creep resistance.…”

Cavitation Erosion Resistance Influence of Material Properties

“…Better mechanical properties due to fine grain for steel also confirmed in Ref. [32], however, corse grain size in high entropy alloys or low nickel austenitic stainless steel [42] results in high ductility. Small grain sizes ensure good CER also for applying coatings [43], even 3 to 6 time better [44] than pure steel.…”

“…6). On the other side, high entropy alloys [32] with low yield strength have better CER than 316L stainless steel.…”

Corrosion resistance mechanism of the passive films formed on as-cast FeCoCrNiMn high-entropy alloy

“…This indicates higher stability of the passive films on the surface of as-cast FeCoCrNiMn alloys than that on stainless steels. The high stability of the passive films on the surface of as-cast FeCoCrNiMn alloys could be attributed to the both of synergistic effect of high mixing entropy and sluggish diffusion [16]. In addition, Cr, Co and Ni which are highly corrosion-resistant elements in as-cast FeCoCrNiMn alloys, can facilitate to form protective passive film in alkaline solution [17].…”