Preparation of Electro-deposited Ni-Mo-Al Coating and Its Properties
Ni-Mo-Al coatings were prepared on Ni alloy by electrodeposition method. The effects of current density, frequency, duty cycle and electrodeposition time on mass percentages of Al of Ni-Mo-Al coatings were researched, respectively. The properties of wear weight loss and friction coefficients were investigated respectively. Ni-Mo-Al coatings were characterized with inductively coupled plasma-atomic emission spectroscopy (ICP-AES), energy-dispersive analyses of X-ray (EDAX), scanning electron microcopy (SEM), and X-ray diffraction (XRD) techniques, respectively. When electro-deposition parameters: current density 18.5 A/dm 2, frequency 5000 Hz, duty cycle 0.5 and electrodeposition time 20 min, mass percentages of Al of Ni-Mo-Al coating is as high as 2.04%. Ni-Mo-Al coatings show higher wear weight loss and lower friction coefficient compared with those of Ni-Mo coatings. The wear weight loss of Ni-Mo-Al coating is 1.27 times higher than that of the Ni-Mo coating. The friction coefficient of Ni-Mo and Ni-Mo-Al coatings are 0.816 and 0.540 respectively. The Ni-Mo and Ni-Mo-Al coatings have similar nodular microstructure. The nodules of Ni-Mo-Al coating are smaller than those of the Ni-Mo coating. The parts of nickel are replaced by Mo and Al respectively in the Ni lattice.
Preparation of electrodeposited Mo-Ni coating and its spectral properties.
Mo-Ni coatings were prepared on Ni alloy by electrodeposition method. The properties of microhardness, wear weight loss and friction coefficients, and thermal expansion of the coatings were investigated, respectively. Mo-Ni coatings were characterized with inductively coupled plasma-atomic emission spectroscopy (ICP-AES), energy-dispersive analyses of X-ray (EDAX), scanning electron microcopy (SEM), and X-ray diffraction (XRD) techniques, respectively. Mo-Ni coating shows higher microhardness, lower wear weight loss and friction coefficient compared with those of Ni alloy. The microhardness of Mo-Ni coating is as high as 518 HV, which is 72.67% higher than that of the Ni alloy (300 HV). The wear weight losses of Mo-Ni coating is 1.94 times lower than that of Ni alloy. The friction coefficient of Ni alloy and Mo-Ni coating are 0.640 and 0.559 respectively. The physical thermal expansion curve of Ni alloy has two the peaks in the ranges of 100-120 and 570-640 degrees C respectively; and that of Ni alloy+Mo-Ni coating has one the peaks in the ranges of 570-640 degrees C. The peak of the physical thermal expansion curve of Ni alloy+Mo-Ni coating in the ranges of 570-640 degrees C is much smaller than that of the Ni alloy. Because the part of nickel was replaced by molybdenum in the Ni lattice, molybdenum decreases the lattices transformation of nickel (bcc --> fcc). The reason for the formation of the small peak of the physical thermal expansion curve of Ni alloy+Mo-Ni coating in the ranges of 595-625 degrees C is the changes of MoNi4 and MoNi from the semi-crystalline structure to the crystalline structure respectively.
Properties of a monopivot centrifugal blood pump manufactured by 3D printing
An impeller the same geometry as the impeller of a commercial monopivot cardiopulmonary bypass pump was manufactured using 3D printing. The 3D-printed impeller was integrated into the pump casing of the commercially available pump to form a 3D-printed pump model. The surface roughness of the impeller, the hydraulic performance, the axial displacement of the rotating impeller, and the hemolytic properties of the 3D-printed model were measured and compared with those of the commercially available model. Although the surface roughness of the 3D-printed model was significantly larger than that of the commercially available model, the hydraulic performance of the two models almost coincided. The hemolysis level of the 3D-printed model roughly coincided with that of the commercially available model under low-pressure head conditions, but increased greatly under high-pressure head conditions, as a result of the narrow gap between the rotating impeller and the pump casing. The gap became narrow under high-pressure head conditions, because the axial thrust applied to the impeller increased with increasing impeller rotational speed. Moreover, the axial displacement of the rotating impeller was twice that of the commercially available model, confirming that the elastic deformation of the 3D-printed impeller was larger than that of the commercially available impeller. These results suggest that trial models manufactured by 3D printing can reproduce the hydraulic performance of the commercial product. However, both the surface roughness and the deformation of the trial models must be considered to precisely evaluate the hemolytic properties of the model.