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In order to further improve the wear resistance of Fe-Cr-C surfacing alloy, Fe-Cr-C wear-resistant surfacing alloy layers with different B addition amounts were prepared on the surface of Q235 steel by adjusting the amount of ferroboron powder added to the surfacing alloy powder using plasma powder surfacing technology.The effects of B addition amount on the microstructure, phase composition and wear resistance of Fe-Cr-C surfacing alloy were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), abrasive wear tests and other analysis and testing methods.Results showed that when the addition amount of B was 0, the microstructure of the surfacing alloy was composed of dendritic Fe and chrysanthemum-like (Fe, Cr)7(C, B)3＋Fe eutectic structure.With the increase of B addition amount, the volume fraction of the (Fe, Cr)7(C, B)3 hard phase in the surfacing layer increased.After the precipitation amount of the (Fe, Cr)7(C, B)3 phase reached a certain value, the primary B0.7Fe3C0.3 phase was formed.When the B addition amount was 20.0%(mass fraction), a large amount of the (Fe, Cr)2 B hard phase was precipitated.The hardness of the surfacing layer showed an overall trend of rising-steep drop-rising, and the hardness of the B-10 sample reached 63.1 HRC.The results of the abrasive wear test showed that the wear resistance of the surfacing alloy layer exhibited an trend of upward-flat- upward, and the wear resistance of the B-20 sample increased to 2.8 times that of the B-0 sample.

Through analyzing 38 sets of nozzle failure during hydraulic jet fracturing, it is found that the main reason of nozzle failure is nozzle drop and inner diameter enlarging caused by high flowrate and high pressure in the first jetting, as well as back pressure impact caused by the jetting fluid. The nozzle needs to be changed for the second jetting. By using law of energy conservation and data of surface jetting simulation, it is calculated that the needed jetting speed for the blockage between casing and formation, speed loss at the nozzle, speed loss to resist hydrostatic column pressure, and speed loss caused by flow back fluid, and the surface critical discharge rate and corresponding depth are obtained. When performing the jetting and fracturing tests on 3 horizontal wells with 21 sections, the discharge rate for the first section is higher than the critical discharge rate, and the following sections are using nozzle protective method. The success on 19 sections proved the method a reliable way to increasing the nozzle lifetime. In 2012, hydraulic jetting fracturing was performed with small proppant volume in reservoirs like bottom water driven reservoir in ChangQing area, and 1 to 2 times of fracturing BHA changing were decreased, which increased the production efficiency and decreased the operation cost. [ABSTRACT FROM AUTHOR]