Metal Injection Moulding (MIM) in Aerospace Industry

Metal injection Moulding (MIM) is an emerging manufacturing technology across the world for the small, complex, precise and net shape metal parts. MIM technology evolved from Plastic Injection Moulding and Powder Metallurgy.

MIM has been used primarily in the defence sectors and the other important sectors such as  consumer goods, sports, tele-communication devices, automotive, hand and power tools. In the recent times, it has gained popularity in the global aerospace industries as well.

The Aerospace industry demands parts with highest quality, innovative designs with better part performance and MIM is here to meet this challenge.

MIM has the following inherent capabilities, because of which it is one of the best suitable manufacturing processes for small and complex metal parts for Aerospace applications:

  • Cost reduction: MIM has the potential to enable component cost reduction, based on its near-net shape capability, which presents the opportunity to reduce process steps.
  • Efficient resource utilisation: MIM offers improved resource efficiency, particularly regards to high material utilisation levels and lower energy consumption relative to competing, conventional manufacturing processes.
  • Improved design freedom: Increased design freedom compared with conventional manufacturing processes.
  • Wider material choice: MIM offers an improved choice of material compared with conventional processing, as nearly every alloy can be made available in powder form to be consolidated by sintering.

MIM technology has found several applications in the aerospace sector, including high performance engine components like HPC Stator vanes in high pressure compressor section of jet engines, seatbelt parts, latches, fittings, spray nozzles, vane arm, adjustment levers, frame and plate parts in armature assembly in servo motors used in Aircraft turbine system, electrical connectors for wire-harness system in the aircraft.

Wide Material Choices through MIM for Aerospace Industry:

MIM can manufacture most of the alloys offered by wrought and cast route for Aerospace applications. MIM offers an improved choice of materials compared with conventional processing.

Primary MIM materials for aerospace applications include stainless steels (SS 17-4PH, 316L), 304L, Soft magnetic materials Fe-Ni alloys like Fe-50 Ni, Nickel base superalloys (Hastelloy X,

Inconel 625, 713C and 718, Nimonic 90 and 80A) and variants. Titanium alloys Ti-6Al-4V and TiAl are also can be used.

MIM’s ability to produce complex, high-volume, high-performance titanium components offers attractive possibilities to reduce aircraft weight.

MIM materials have various advantages like homogeneous microstructure and isotropic material properties with no interconnected porosity which is normally present in the PM parts. Hence, MIM is suitable manufacturing process for complex aerospace parts with higher part performance and material properties at par with wrought and cast route.

Material Category Material Name Properties Applications
Stainless Steel MIM SS 316L Corrosion resistance, non-magnetic, ductile

Hardness : 100 HRB max

UTS           : 450 MPa                        YS              : 150 MPa                       %E             : 40 min

 Electrical connectors for wire-harness system
Stainless Steel MIM SS 17-4 PH Corrosion resistance, magnetic, higher strength and hardness

Hardness : 35 – 43 HRC                 UTS           : 1070 MPa min                   YS              : 970 MPa min                     %E             : 4 min

Above properties in  solution annealed and H900 aged condition

 Seatbelt parts, latches, fittings
Nickel base super alloys INCONEL 718 Good tensile, fatigue, creep, and rupture strength at elevated temperature and higher corrosion resistance

Hardness : 35 HRC                 UTS           : 1180 MPa                        YS              : 900 MPa                       %E             : 5 min

Above properties in solution annealed and aged condition

 Spray nozzles, vane arm adjustment levers, vanes
INCONEL 713 LC Higher resistance to oxidation and thermal fatigue and outstanding structural stability

Hardness : 20 HRC

UTS           : 900 MPa                        YS              : 650 MPa                       %E             : 5 min

 HPC Stator vanes in high pressure compressor section of jet engines, sealing plates
Fe-Ni Soft magnetic materials Fe-50Ni High permeability and low coercive field

Hardness : 100 HRB max             UTS           : 400 MPa                        YS              : 100 MPa                       %E             : 25 min

 Frame, plate, coil housing, bobbin parts in armature assembly in servo motors used in Aircraft turbine system
Titanium alloys Ti-6Al-4V High strength-to-weight ratio, resistance to high temperatures, and excellent corrosion resistance    Hardness : 30 HRC max             UTS           : 900 MPa                        YS              : 830 MPa                       %E             : 10 min Structural applications and vanes for engines

MIM is inherently a lean manufacturing process as it produces a near net shape component with fewer production steps and requires few secondary finishing operations. MIM process can be controlled to get the consistent high-volume production with proper process control measures and quality system. As MIM has fewer steps in the manufacturing process, it is easy to trace the manufacturing process from raw material receipt stage to the stage of despatch of finish goods. This is advantageous for Aerospace part manufacturing.

Thus, MIM is used as a proven manufacturing process for complex Aerospace parts with high quality & regulatory requirement.