Additive manufacturing process development for realization of Preburner Pump Impeller of LOX hydrocarbon based rocket engine using AlSi10Mg material
Creators: name:  R. VERMA 
name:   A. ALEX 
Publisher: name: Proceedings of  the 9th European Conference for Aerospace Sciences. Lille, France, 27 June - 1 July, 2022
Year: 2022
Subjects: STRUCTURES
MATERIALS. ADDITIVE MANUFACTURING

description: Fuel pump of LOX hydrocarbon based rocket engine employ impeller realized through investment casting process and made by aluminum alloy AL4-BM-T6-3. The pump impeller is shrouded, centrifugal flow impeller with backward curved blades. It operates with inlet pressure provided by the inducer and delivers the fuel at the required flow rate and pressure to thrust chamber. The rejection rate of the realised hardware is high, due to the inherent casting defect. Hence an alternate route for impeller realisation is thought of. The present study has been carried out to realised Preburner Pump Impeller of LOX hydrocarbon based rocket engine through Additive manufacturing process using AlSi10Mg material in place investment casting route. Additive manufacturing (AM), which is also known as 3D printing, refers to an evolutionary manufacturing technology that substitutes conventionally manufactured products, including castings, forgings, assemblies with parts consolidation, etc. Additive manufacturing enables the realisation of complex parts with reduced lead time, with minimum material, and empowers the designer to combine multiple process steps into a single design. On investigation it was found that the part was most amenable to additive manufacturing. The size of the part could easily fit into a 3D printer available .The AlSi10Mg powder, the basic feedstock was freely available and was being widely used for additive manufacturing. The vanes could easily be printed without supports by suitably orienting the parts. The entire part could be realized in one piece eliminating any further joining process. Available results on Additive Manufacturing gave the confidence that parts would be free of defects. Considering the advantages it was decided to realize the part by Additive Manufacturing.Due to non-availability Cast aluminum alloy AL4-BM-T6-3 power material, AlSi10Mg powder materials is preferred which is equivalent to cast aluminum alloy AL4-BM-T6-3 materials. To ensure the quality of the product, the feedstock powder used is virgin and characterisation of feedstock is carried out before realisation. Preburner Pump impeller along with test coupons (X, Y, Z 45o) to XY plane direction (Z is build direction) are realised in a qualified machine with optimum process parameter using AlSi10Mg powder. After printing, Preburner pump impeller along with the test coupons were stress relieved at 300 C for 2 hour and solution treatment at 530 C for 6 hours followed by air cooling. Further, aging is carried out at 160 C for 6 hours followed by air cooling as per ASTM F3318 18.To validate the soundness of specimen level, Non-Destructive Testing (DP RT) of test coupons was carried out, followed by the mechanical testing in X, Y, Z 45o to XY plane direction (ambient temperature tensile testing and impact testing). The chemical composition analysis on specimens was carried out and it meets the specification. Microstructure observed in X, Y, Z 45revealed fine Si particles distributed around Al matrix. At product level validation, the parts are subjected to Non-Destructive Testing (DP RT) before after machining, and no significant defects are observed. Videoscopic inspections are also carried out in all accessible flow path area and no projection/ are observed. Dimensional inspection is carried out and meeting the requirement. At present product level static balancing is in progress before doing spin test. As achieved mechanical strength is significantly higher than the strength required to the Preburner Pump Impeller during operating condition. Hence additively manufactured Preburner Pump Impeller is now cleared for doing spin test at ambient temperature which will indicates that the hardware confirms to system requirements. It is found that Additive Manufacturing scores over casting in terms of time, quality, cost benefits and weight savings which are of prime importance in space sector. Future scope lies in the application of design for additive manufacturing (DFAM) towards optimization. Keywords AlSi10Mg, LOX, Additive manufacturing, Powder bed fusion ACKNOWLEDGEMENTS The authors highly acknowledge Shri. Thomas Tharian, (GM MDP), Shri Aby Isaac, DM, SC-TCF of LPSC, Valiamala, and M/s Wipro Bangalore for the supports rendered for bringing out this paper. REFERENCES ASTM E 8M ASTM F3318 18