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The corrosion resistance and biocompatibility of a novel Fe50Cr18Mo10C20Si2 metallic glass (Fe–MG), are studied by electrochemical measurements and indirect contacting cytotoxicity assays for biomedical applications. In Hank's solution, the Fe–MG shows better corrosion resistance than SS316L, evidenced by the larger polarization resistance in the potentiodynamic and electrochemical impedance spectroscopy (EIS) tests, and the lower amounts of released metallic ions during the immersion test. X-ray photoelectron spectroscopy (XPS) analyses show that a double-layer passive film, consisting of outer Fe-rich oxide and inner Cr-rich oxide, is formed on the Fe–MG. The stable passive film, together with the defect-free nature of the metallic glass, accounts for good corrosion resistance. In addition, in vitro tests suggest that the Fe–MG extracts have good blood compatibility, and no cytotoxicity to murine fibroblast cells. Compared with other Fe-based metallic glasses, the prepared novel Fe–MG contains no toxic elements, and shows a low corrosion rate. [ABSTRACT FROM AUTHOR]

In order to obtain a laser-cladded coating with no cracking and good corrosion resistance, this paper investigated laser cladding of a mixture of 17-4PH stainless steel and Ni60 powders on ASTM 1045 steel substrate. The surface cracking, mechanical properties and corrosion resistance of the coatings were assessed by various characterization methods. The experimental results demonstrated that a crack-free coating can be obtained by adding 30% (or above) 17-4PH stainless steel into Ni60 alloy. The mechanical properties of the coatings were determined by adding 17-4PH, but stabilized at about 79% of pure Ni60 alloy, which is acceptable considering the benefit of elimination of surface cracking. Decrease in the mechanical properties were caused by the dilution of the strengthening elements and reduction of population of hard phases. Composite coating having 30% of 17-4PH also exhibited the smallest corrosion current, lowest corrosion potential and slowest corrosion rate, and therefore the best corrosion resistance. [ABSTRACT FROM AUTHOR]

H13 steel is often damaged by wear, erosion, and thermal fatigue. It is one of the essential methods to improve the service life of H13 steel by preparing a coating on it. Due to the advantages of high melting point, good wear, and corrosion resistance of Mo, Mo coating was fabricated on H13 steel by electro spark deposition (ESD) process in this study. The influences of the depositing parameters (deposition power, discharge frequency, and specific deposition time) on the roughness of the coating, thickness, and properties were investigated in detail. The optimized depositing parameters were obtained by comparing roughness, thickness, and crack performance of the coating. The results show that the cross-section of the coating mainly consisted of strengthening zone and transition zone. Metallurgical bonding was formed between the coating and substrate. The Mo coating mainly consisted of Fe9.7Mo0.3, Fe-Cr, FeMo, and Fe2Mo cemented carbide phases, and an amorphous phase. The Mo coating had better microhardness, wear, and corrosion resistance than substrate, which could significantly improve the service life of the H13 steel. [ABSTRACT FROM AUTHOR]

In this essay, a femtosecond laser is used to create various structures on the surface of Zr-based amorphous material. Through the raster scan mode, under different laser energy densities, LIPSS (Laser-induced periodic surface structures), SWPSS (Super-wavelength periodic surface structure) and microporous structures were obtained in the experiment. Various surface properties of the micro-nano structures were tested. Experimental results illuminate that laser energy fluence is the key to determining the formation of nano- and microscale structures. The laser treatment greatly improves the surface roughness of the sample. The laser texture converts the originally hydrophilic specimen surface into a hydrophobic surface, which greatly reduces the material's surface energy. We found that all the formed surface structures can reduce the adhesion of Escherichia coli and Staphylococcus aureus. In detail, the adhesion rate of bacteria on the surface of SWPSS is the lowest. This article comprehensively discusses the influence mechanism of nano- and microscale structures on bacterial adhesion from four aspects: surface roughness, hydrophobicity, surface energy, and surface morphology. The study manifest that the period and amplitude of the nano- and microscale structures are the keys to bacterial adhesion. In addition, experiments have shown that nano- and microscale structures can effectively improve the corrosion resistance of zirconium-based bulk metallic glass. [ABSTRACT FROM AUTHOR]

Due to their bioinert nature, titanium alloys show poor bone-implant integration and insufficient osseointegration in vivo. In this study, a series of low elastic modulus bioactive titanium alloys with a nominal composition of Ti-13Nb-13Zr-1.25 Mg (wt%) were prepared using mechanical alloying and spark plasma sintering techniques. The microstructures, mechanical properties, degradation behaviors and in vitro bioactivities of these alloys were systematically investigated. After sintering at 700 °C, the α-Ti, β-Ti and Nb (Zr)-rich phases were present, and the Mg was uniformly distributed. In addition to above-mentioned phases, the α″ phase was found after sintering at 800 °C or 900 °C. The density, elastic modulus, yield strength, ultimate compressive strength and corrosion resistance all increased with increasing sintering temperature. After sintering at 900 °C, the alloy exhibited high density (99.8%), good compressive strength (1417.2 MPa) and excellent corrosion resistance. In addition, it had a lower elastic modulus (~69 GPa) than that of the biomedical alloy Ti–13Nb–13Zr (~80 GPa). In vitro experiments showed that the alloys sintered at either 800 °C or 900 °C promoted cell adhesion and proliferation. However, the alloy sintered at 700 °C inhibited cell proliferation, which was due to the greater release of Mg2+. Thus, the optimally-processed Ti-Nb-Zr-Mg alloy sintered at 900 °C shows immense potential as a biomedical material. [Display omitted] • Ti-Nb-Zr-Mg alloys with low modulus were fabricated by MA and SPS. • Higher sintering temperature promoted the formation of α″ phase. • Mg element reduced the corrosion resistance of Ti-Nb-Zr matrix. • The mode of Mg2+ release was affected by sintering temperature. • The sustained release of Mg2+ was beneficial to the cell viability and proliferation. [ABSTRACT FROM AUTHOR]

• FeCoCrNiMoSi x (x = 0.5, 1.0, 1.5) HEAs were fabricated by SPS under 1150 °C. • Hardness of FeCoCrNiMoSi 1.5 reached 1186 HV. • High corrosion potential of Si makes FeCoCrNiMoSi 1.5 exhibits great corrosion resistance. • The oxidation properties FeCoCrNiMoSi 0.5 were greater than that of other FeCoCrNiMo HEAs. • Different properties can be obtained through controlling Si content. FeCoCrNiMoSi x (x = 0.5, 1.0, 1.5) high-entropy alloys (HEAs) were successfully fabricated by spark plasma sintering (SPS). The microstructure, tribological properties, oxidation behaviors and corrosion resistance of the HEAs were systematically investigated. The experimental results showed that the microstructure mainly consisted of Fe-rich face-centered-cubic (FCC) phase, Mo-rich FCC phase solid solution and various Si-rich intermetallics, where the elevated Si content coarsened the primary Mo-rich phase into dendritic eventually. These Mo-rich dendrites possessed strong covalent-dominant atomic bonds that enhanced the microhardness (from 725 to 1186 HV) and wear resistance. The FeCoCrNiMoSi 0.5 HEA exhibited an outstanding combination of relatively high wear resistance and the strongest oxidation resistance under 800 °C among the three alloy compositions. The corrosion resistance of HEAs showed an increasing trend with the elevated Si content, and FeCoCrNiMoSi 1.5 presented the best performance. [ABSTRACT FROM AUTHOR]

High-speed laser cladding technology can significantly improve the efficiency of coating preparation and effectively widen the application range of laser cladding. In this study, the Ni45 powders were deposited on steel substrate by traditional low speed laser cladding and high-speed laser cladding process, respectively. The cladding efficiency, surface forming, cross-sectional microstructure, microhardness, wear and corrosion resistance properties of the traditional and high-speed laser cladded Ni45 alloy coatings were compared. It can be seen that the thickness of the high-speed laser cladding coating was much thinner than that of the traditional laser cladding coating. Compared with traditional laser cladding, high-speed laser cladding could achieve a cladding speed of 76.86 m/min and a cladding efficiency of 156.79 cm2/min. The microstructure of the two kinds of coatings shows the same growth law, but the microstructure in high-speed laser cladding was smaller and denser, and the columnar crystal interval was narrower, only about 6 μm. It is found that the cooling rate of the traditional laser cladding coating was smaller than that of the high-speed laser cladding, and as the cladding speed increased, the cooling rate became higher and higher. The cross-section microhardness of the traditional laser cladding coating was relatively uniform of 337 HV 0.2 , while the microhardness of high-speed laser cladding surface increased to about 543 HV 0.2. In addition, the wear and corrosion resistance of high-speed laser cladded coatings were better than that of traditional laser cladded coatings. As the cladding speed increased, the wear and corrosion resistance of the cladded coatings became better. • High-speed laser cladding coating had low roughness and thin coating. • The cooling rate increased exponentially with a decrease of secondary dendrite arm. • The wear and corrosion resistance increased with the increase of cladding speed. • The microstructure was refined continuously with the increase of cladding speed. [ABSTRACT FROM AUTHOR]