Cavitation wear of Eurofer 97, Cr18Ni10Ti and 42HNM alloys

The microstructure, hardness and cavitation wear of Eurofer 97, Cr18Ni10Ti and 42HNM have been investigated. It was revealed that the cavitation resistance of the 42HNM alloy is by an order of magnitude higher than that of the Cr18Ni10Ti steel and 16 times higher than that of the Eurofer 97 steel. Alloy 42HNM has the highest microhardness (249 kg/mm2) of all the investigated materials, which explains its high cavitation resistance. The microhardness values of the Cr18Ni10Ti steel and the Eurofer 97 were 196.2 kg/mm2 and 207.2 kg/mm2, respectively. The rate of cavitation wear of the austenitic steel Cr18Ni10Ti is 2.6 times lower than that of the martensitic Eurofer 97.

Contrasting Water Use, Stomatal Regulation, Embolism Resistance, and Drought Responses of Two Co-Occurring Mangroves

The physiological mechanisms underlying drought responses are poorly documented in mangroves, which experience nearly constant exposure to saline water. We measured gas exchange, foliar abscisic acid (ABA) concentration, and vulnerability to embolism in a soil water-withholding experiment of two co-occurring mangroves, Avicennia marina (Forsskål) Vierhapper (Verbenaceae) and Bruguiera gymnorrhiza (L.) Savigny (Rhizophoraceae). A. marina showed higher photosynthesis and transpiration than B. gymnorrhiza under well-watered conditions. Cavitation resistance differed significantly between species, with 50% cavitation occurring at a water potential (P50) of −8.30 MPa for A. marina and −2.83 MPa for B. gymnorrhiza. This large difference in cavitation resistance was associated with differences in stomatal closure and leaf wilting. The rapid stomatal closure of B. gymnorrhiza was correlated with ABA accumulation as water potential declined. Meanwhile, stomatal closure and declining water potentials in A. marina were not associated with ABA accumulation. The safety margins, calculated as the difference between stomatal closure and embolism spread, differed between these two species (1.59 MPa for A. marina vs. 0.52 MPa for B. gymnorrhiza). Therefore, A. marina adopts a drought tolerance strategy with high cavitation resistance, while B. gymnorrhiza uses a drought avoidance-like strategy with ABA-related sensitive stomatal control to protect its vulnerable xylem.

Influence of the polymer matrix type on cavitation resistance of composites

Cavitation resistance of polymer matrix / basalt powder composites was determined in this work. Two types of composites were tested: epoxy resin / basalt powder composite and polyester resin / basalt powder composite. In both cases, a basalt powder was used as reinforcement in the resin (grain size 20μm, in the amount of 15 wt%). An ultrasonic vibration method with a stationary sample was used to test the cavitation resistance of composites in laboratory conditions. The change in sample mass with test time was monitored to define cavitation rate. Scanning electron microscopy was used to monitor the morphology of composites surface damage.

Microstructural and Cavitation Erosion Behavior of the CuAlNi Shape Memory Alloy

Microstructural and cavitation erosion testing was carried out on Cu-12.8Al-4.1Ni (wt. %) shape memory alloy (SMA) samples produced by continuous casting followed by heat treatment consisting of solution annealing at 885 °C for 60 min and, later, water quenching. Cavitation resistance testing was applied using a standard ultrasonic vibratory cavitation set up with stationary specimen. Surface changes during the cavitation were monitored by metallographic analysis using an optical microscope (OM), atomic force microscope (AFM), and scanning electron microscope (SEM) as well as by weight measurements. The results revealed a martensite microstructure after both casting and quenching. Microhardness value was higher after water quenching than in the as-cast state. After 420 min of cavitation exposure, a negligible mass loss was noticed for both samples. Based on the obtained results, both samples showed excellent cavitation resistance. Mass loss and morphological analysis of the formed pits indicated better cavitation resistance for the as-cast state (L).

Thermal Spraying of FeMnCrSi Alloys: An Overview

FeMnCrSi alloys have been developed and studied over the past several years with an emphasis on their use as coatings on CA6NM stainless steel hydroturbine components. Much of the work conducted has focused on the optimization of cavitation resistance through chemical composition changes, the use of different thermal spraying (ASP, HVOF, HVAF) and welding (PTA) processes, and post-treatments such as shot-peening, cold working, and PTA remelting. The aim of this current work is to present a compilation of published articles that report on the research that has been done. Among the trends observed is that coating density and cavitation resistance improve with increasing particle velocity, particularly for HVOF-kerosene spraying. In regard to post-treatments, cold working was found to most effective, reducing cavitation mass loss (in PTA FeMnCrSi coatings) by a factor of nearly two.

Influence of Fuel/Oxygen Ratio on Coating Properties and Cavitation Resistance of WC and Cr3C2 Cermet Coatings Deposited by HVOF

Hydroelectric turbines are strongly affected by cavitation and the damage it can cause to critical part surfaces and profiles. The study of thermal spray processes and materials is thus relevant to improving turbine performance. The main objective of this work is to evaluate the influence of fuel-oxygen ratio on tungsten- and chromium-carbide cermet coatings deposited by HVOF. Particle velocity and temperature were measured as were coating hardness, porosity, and cavitation resistance. Higher particle velocities were obtained at higher fuel ratios, producing harder, denser coatings with better cavitation resistance. Based on test results, the wear mechanism starts with the nucleation of the cavitation that occurs in the pores, resulting in the formation of craters and the eventual detachment of lamellae as indicated by the smoothness of the surface.