Structure of Micro-nano WC-10Co4Cr Coating and Cavitation Erosion Resistance in NaCl Solution

Cavitation erosion （CE） is the predominant cause for the failure of overflow components in fluid machinery. Advanced coatings have provided an effective solution to cavitation erosion due to the rapid development of surface engineering techniques. However, the influence of coating structures on CE resistance has not been sys- tematically studied. To better understand their relationship, micro-nano and conventional WC-10Co4Cr cermet coat- ings are deposited by high velocity oxygen fuel spray- ing（HVOF）, and their microstructures are analyzed by OM, SEM and XRD. Meanwhile, characterizations of mechan- ical and electrochemical properties of the coatings are carried out, as well as the coatings＇ resistance to CE in 3.5 wt % NaC1 solution, and the cavitation mechanisms are explored. Results show that micro-nano WC-10Co4Cr coating possesses dense microstructure, excellent mechanical and electrochemical properties, with very low porosity of 0.26 4-0.07% and extraordinary fracture toughness of 5.58 4-0.51 MPa.m1/2. Moreover, the CE resistance of micro-nano coating is enhanced above 50% than conventional coating at the steady CE period in 3.5 wt % NaC1 solution. The superior CE resistance of micro- nano WC-10Co4Cr coating may originate from the unique micro-nano structure and properties, which can effectively obstruct the formation and propagation of CE crack. Thus,a new method is proposed to enhance the CE resistance of WC-10Co4Cr coating by manipulating the microstructure.

Water transport and water use efficiency differ among Populus euphratica Oliv. saplings exposed to saline water irrigation

Populus euphratica Oliv.is a unique woody tree that can be utilized for vegetation restoration in arid and semi-arid areas.The effects of saline water irrigation(0.00, 2.93, 8.78 and 17.55 g/L NaCl solutions) on water transport and water use efficiency(WUE) of P.euphratica saplings were researched for improving the survival of P.euphratica saplings and vegetation restoration in arid and semi-arid areas of Xinjiang, China in 2011.Results showed that hydraulic conductivity and vulnerability to cavitation of P.euphratica saplings were more sensitive in root xylem than in twig xylem when irrigation water salinity increased.Irrigation with saline water concentration less than 8.78 g/L did not affect the growth of P.euphratica saplings, under which they maintained normal water transport in twig xylem through adjustment of anatomical structure of vessels and kept higher WUE and photosynthesis in leaves through adjustment of stomata.However, irrigation with saline water concentration up to 17.55 g/L severely inhibited the photochemical process and WUE of P.euphratica saplings, resulting in severe water-deficit in leaves and a sharp reduction in water transport in xylem.Thus, it is feasible to irrigate P.euphratica forest by using saline groundwater for improving the survival of P.euphratica saplings and vegetation restoration in arid and semi-arid areas of Xinjiang, China.