Diffusion Bonding of CMSX-4 to UDIMET 720 Using PVD-Coated Interfaces and HIP

Abstract

There is an increasing interest in development of manufacturing methods for Dual Property BLISKs, consisting of creep resistant airfoils and fatigue resistant disks bonded together by a durable joint. Optimum heat treatments are, however, very different for creep resistant single crystal CMSX-4 and fatigue resistant polycrystalline Udimet 720 selected in this study, but fortunately the first aging treatment for CMSX-4 (1140°C, 2–6 h, AC) is similar to the partial solution treatment of U 720 HS2 (115°C, 4h, OQ). Based on this, diffusion bonding was performed by HIP at 1120°C and 200 MPa argon pressure for 4 h, followed by cooling to 400°C. Subsequently, a shortened Udimet 720 HS2 two-step aging treatment was adopted by heating to 650°C for 6 h followed by cooling to 400°C, heating to 760°C for 2 h, and finally cooling to R.T. under remaining HIP pressure. Plasma etching followed by thin (80 nm) PVD coating with either nickel or titanium were used to clean and protect the polished surfaces before joining. The selection of coatings was governed by the possibility to reduce oxidized nickel by flushing with hydrogen at 330°C during evacuation of the HIP capsules, and by the large solubility of oxygen in titanium. Hot tensile testing was performed at 750°C on both joined and reference materials subjected to the modified heat treatment. Initially solution treated Udimet 720 and CMSX-4 comprised the reference materials. The testing showed that joints with Ti-PVD coatings were almost as strong as Udimet 720 (although with very limited elongation), while the joints with Ti-PVD coatings were weaker.

Insulating Structural Ceramics Program, Final Report

“…Summaries of these estimations are given in Table 6. Fatigue testing work indicates that the fatigue limit of 23-8N is significantly lower than the nickel based Comparison of the limited data generated for these materials by rotating beam fatigue methods to that determined by Eaton Corp. in a similar manner [37] indicates that fatigue limits for the present estimations deviate a maximum of 4% from a logarithmic interpolation of the Eaton data. Fracture surfaces were not analyzed in detail for these tests.…”

Manufacture and microstructural characterisation of bimetallic gas turbine discs

“…1. The MC forming elements Ti, Ta, and Nb 10,11 are locally accumulated in the precipitates. Elements such as Mo and W were also found, but the partitioning to the precipitates is much lower than for Ti, Ta and Nb.…”

“…2. Other types of carbides/borides, such as M 23 (C,B) 6 (rich in Cr), M 3 B 2 (rich in Cr, Mo and some W, Ti), MB 2 (rich in Cr and some W, Mo) 10 and M 6 C (rich in Mo, W) 11,12 seem to be unlikely because they contain Cr, which was totally absent in the filmlike precipitates.…”

Processing, Microstructure, and Properties of Bimetallic Steel-Ni Alloy Powder HIP

“…A HIP bonding strength with minimal penalties in mechanical properties highly relies on the alloy compositions, HIP cycle, post heat treatment, and interface preparation for cleanliness before HIP, which govern the resulting composition and phases, grain structure, and residual stress at bonding interface. Solid-to-solid HIP diffusion bonding requires low surface roughness, high cleanliness, and oxide-free bonding interface ensured by a physical or chemical interface preparation method prior to HIP [3,22]. The HIP temperature and post-HIP heat treatment shall be carefully balanced to reduce interface voids and prevent severe grain coarsening.…”