Powder Interlayer Bonding (PIB) has been considered as a lower-energy joining technology for nickel-based superalloys compared to conventional methods; such as friction welding. Typically; nickel-based superalloys exhibit high energy requirements for joining due to their high operating temperatures. However; PIB utilizes a localized temperature gradient created by an induction current; reducing the energy requirements for the process. PIB is a solid-state joining method that compresses and heats a powder interlayer between two faying surfaces to produce one joined workpiece. It has been successfully used to bond titanium alloys; and the objectives of this work were to explore its application as a joining method for nickel-based superalloys. Initial results showed that joining nickel-based superalloys via PIB is possible; and bondlines with very little porosity were observed. Further analysis showed that these bonded areas had lower porosity than the base material; suggesting PIB could be a successful joining method for difficult-to-join nickel-based superalloys.

Powder interlayer bonding (PIB) is a novel joining technique, which has been developed to facilitate high-integrity repairs of aerospace components, manufactured from commonly used titanium alloys. The PIB technique utilises an interlayer between complex geometric components which are mated under pressure and a highly localised heating source. In this study, induction heating enabled bonding in an inert fusion zone by use of an oxygen-displacing shielding gas, with particular attention to the initial heating and pressure application. These early stages proved crucial to the elimination of pores and consolidation of the alloy powder, with porosity volume fraction reduced to just 0.5% after just 20 sec at the bonding force. The technique has produced high-integrity bonds in alloys such as Ti-6Al-4V, retaining approximately 90% of the alloy strength in previous studies, offering advantages over established joining methods such as tungsten inert gas (TIG) and plasma arc (PA) welding due to a more highly localised heating and fusion zone. It is believed that powder interlayer bonding can compete against these techniques, providing a more time and cost-effective repair route for net shape components manufactured from a range of alloys with minimal post-processing.

Powder interlayer bonding (PIB) is a joining technique originally developed to enable high-integrity repairs of aerospace components. The technique has previously been employed for the joining of titanium and nickel alloys utilised in the aerospace industry. This study expands on the application of the novel joining technique known as powder interlayer bonding (PIB), to the bonding of γ titanium aluminide (TiAl) material. PIB has been used to facilitate high-integrity joints in gamma titanium aluminides (TiAl), where full densification of the joint was achieved. The PIB technique described here used a metallic powder interlayer between the two faying surfaces of γ TiAl specimens. Bonds were formed in an inert atmosphere under induction heating. The PIB technique proved capable of producing high-integrity bonds in terms of microstructural evaluation, with very limited porosity retained after the bonding cycle. A brittle Ti 2 Al phase can be produced with heavily oxidised powder which is susceptible to cracking and will negatively affect mechanical properties.

A novel Powder Interlayer Bonding (PIB) process has been developed at Swansea University, and has been demonstrated to show excellent capability of joining various metallic materials commonly used in aerospace gas turbine engines. The most recent PIB studies have focussed on the bonding of Titanium 6Al-4V, with a promising 90% strength retention having been demonstrated. This has led to proposals for PIB to be explored as a potential repair process within the gas turbine industry, for a range of components manufactured from Titanium 6Al-4V. Example components identified as potential repair applications for PIB include large single piece components such as bladed discs (BLISKs), as well as thin wall case structures for which there are currently very limited options for repair. While early feasibility studies have shown great promise for PIB with respect to filling these voids in repair capability, they have typically involved bonding of small-scale flat coupons which do not bear any resemblance to the shape and size of these components. The purpose of this EngD project was therefore to adapt the PIB principles, producing a machine capable of joining coupons of upscaled size and geometric complexity. It was hoped that this would help “bridge the gap” between small-scale feasibility trials and industry adaptations of the technique. The PIB principles developed at Swansea University have been successfully implemented in a new bespoke joining machine which remains in-situ at Swansea University. Small-scale bonds produced using identical parameter sets were first compared using both legacy and newly developed apparatus to validate the bespoke machine. The newly developed system was shown to produce bonds of equivalent quality with respect to upset of the fusion zone, and key powder consolidation characteristics. Moreover, additional benefits were realised in improved control, reliability and repeatability of bonding using the newly developed system. Attention was then turned to investigation of coupon interface geometry effects on key PIB bonding outputs, with a total of four interface geometries tested. Aggressively curved surfaces were shown to reduce fusion zone upset at the expense of consistent powder collapse across the interface, while mild surface changes were observed to promote powder consolidation at the expense of some dimensional loss. This led to the down selection of a 50:1 curved interface geometry which appeared to demonstrate adequate process capability for the proposed application, while also balancing coupon deformation with effective powder consolidation behaviour. Upscaled coupon testing focussed on the isolation of optimised parameter sets for bonding coupons of differing cross sections in a flat “plate and boss” interface geometry. Optimised parameters were shown to produce bonds featuring a high level of microstructural retention in combination with effective pore closure and acceptable fusion zone upset. Read across of this parameter set was successfully implemented on similarly sized coupons, mated with the down selected 50:1 curved interface geometry, in addition to a further trial involving oversized flat near-net shape BLISK aerofoil coupons. The success of these trials demonstrates the capability of PIB with respect to bonding geometries representative of the components requiring repair in the proposed applications. Finally, potential avenues for investigation which could benefit the continued adaptation of PIB for these applications were highlighted.