Pengju Xue

An Integrated Forming Process for Manufacturing Ti6Al4V Impeller with a Functional Coating Layer Using Hot Isostatic Pressing

The complex aircraft components are difficult to manufacture because of their complicated shapes and high requirements of mechanical properties. Besides, those components usually need a functional coating layer on the surface to improve the reliability, which adds an extra production cycle after manufactured. In this study, an integrated forming process was proposed to manufacture a complex-shaped impeller together with the surface coating layer using hot isostatic pressing (HIP). In this new process, an HIP mold with the graphite core pre-deposited a Ni coating layer was designed and conducted with the HIP experiment. The results show that the manufactured impeller had a dimensional precision of 0.15 mm. The scanning electron microscope/X-ray diffraction (SEM/XRD) analyses show that the internal microstructure was compact with α + β phases and the surface had a uniform Ti2Ni/TiNi coating layer. The mechanical experiments show that the HIPped specimens had a 70 MPa higher yield strength and 95 MPa higher tensile strength than the same-size forgings. Besides, a Ti2Ni/TiNi coating layer was formed on the surface of the impeller and the hardness and wear resistance had an obvious improvement. All the results show that the new process was successfully applied to near net shaping of an integrated Ti6Al4V impeller with a functional coating layer.

Effect of Tooling Material on the Internal Surface Quality of Ti6Al4V Parts Fabricated by Hot Isostatic Pressing

For the net-shape hot isostatic pressing (HIP) process, control of the internal surface roughness of as-HIPped parts remains a challenge for practical engineering. To reveal the evolution mechanism of the internal surface of the parts during the HIP process, the effect of different tooling materials (H13, T8, Cr12 steel, and graphite) as internal cores on the interfacial diffusion and surface roughness was systematically studied.