High Performance Alloys Developed for Turbochargers

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1 High Performance Alloys Developed for Turbochargers Kazuaki Nishino, Hiroyuki Kawaura, Kouji Tanaka, Toshio Horie, Takashi Saito, Hiroshi Uchida NV (FOD) Mg 300GPa6.6 Ip High performance were developed in order to improve the performance of turbochargers for automotive engines by leaps and bounds. The developed are (1) a γ -TiAl alloy for turbine wheels, which improved the high temperature oxidation resistance by a new surface treatment and (2) a heat-resistant magnesium alloy for compressor impellers with a specific high temperature strength superior to that of the conventional aluminum alloy, and (3) a high modulus steel for turbine shafts with a Young's modulus of 300GPa strengthened by the dispersion of titanium borides. The application of these developed for rotating parts can reduce the inertia moment (Ip) by 42% and can increase the resonance frequency of shaft vibration by 44%.

2 1970 NV Si 3 N 4 FOD Foreign Object Damage NV SCr GPa NV (TiAl) Ni1/2 Ni TiAlK IC 713C1/3 FOD TiAlNi C Al2/3Mg 300GPa Target of developed for rotating parts. Turbine wheel Compressor impeller Turbine shaft Conventional Ni-base superalloy (Inconel 713C) <ρ=7.9> Al alloy (AC4D) <ρ=2.7> SCr steel Developed TiAl alloy High resistance to FOD Oxidation resistance at 950 C ρ Heat resistant Mg alloy Strength at 150 C equal to Al alloy ρ High Modulus Steel <E=210GPa> <E=300GPa> <ρ=7.8> <ρ=6.6> ρ : Specific gravity Ε : Young's modulus

3 TiAl Mg 300GPa FOD φ1mm He He200m/s 550m/s 550m/s 50mm 21rpm FOD 713C TiAlTi-47mol%Al NbCr B Fig. Ti-Al FOD FOD TiAl NbWMoSi Ni NbFOD TiAl 900 C Sensor Helium gas Oscilloscope Steel ball<φ1mm> Maximum speed:550m/s Valve Sabot Helium gas cylinder (0.25~0.99Mpa) Thickness of wheel Min.: 0.7mm Thickness of wheel Min.:1.6mm Ti-47Al Ti-48Al-2Cr-2Nb Ti-47Al-1.7B Ti-47Al-2.0Nb Inconel 713C Ceramics (Si3N4) Impact Velocity, m/sec Damage Damage No Damage Schematic drawing of FOD test set up for TiAl. Effect of impact velocity on foreign object damage of TiAl wheels.

(WO 3 ) Ti-47Al 950 C Nb 713C Compressed air (0.4MPa) Ti-47Al Treating powder (WO3) Spray gun Schematic drawing of surface treatment using shot-blast equipment.

4 (WO 3 ) Ti-47Al 950 C Nb 713C Compressed air (0.4MPa) Ti-47Al Treating powder (WO3) Spray gun Schematic drawing of surface treatment using shot-blast equipment. 50h 200h TiAl FOD 713C 150 C Mg-Al MgAgNd Y250 C Mg-Zn-Ca ( Mm: Ce50 ) Zr Mg-2%Zn-0.8%Ca-2%Mm-0.6%Zr (mass%) Ca Mass Gain (g / m 2 ) C-100hr in exhaust gas atmosphere Ti-47Al Ti-47Al -2Nb Untreated WO3-SB Treated (Ti-47Al) Inconel 713C Composition of exhaust gas O2 CO2 NO CO C3H6 SO2 H2O N vol% 7.4 vol% 1000 ppm 760 ppm 600 ppm 300 ppm 3.5 vol% Bal. Mass gain due to cyclic oxidation in exhaust gas. (a) untreated (after 50 hr) (b) WO 3 -SB treated (after 200 hr ) Appearance of untreated (a) and WO 3 -SB treated (b) Ti-47Al specimens oxidized at 950 C in exhaust gas after cyclic oxidation tests.

465 C24h 200 C2h ( ) 100 CAZ91 Al150 C1.3 150 C 100h0.

5 465 C24h 200 C2h ( ) 100 CAZ91 Al150 C C 100h0.1 Al Specific Tensile Strength, MPa AC4D-T6 (Al alloy) Developed Mg alloy AZ91 (Mg alloy) Temperature, C 250 Specific tensile strength of developed Mg alloy (Mg-2%Zn-0.8%Ca-2%Mm- 0.6%Zr). 5nm Zr Mg-Zn-Ca TiB 2 Specific Creep Strength at 150 C MPa [100hr, 0.1% creep strain] AC4D-T6 Developed Mg alloy AC4D-T6 Developed Mg alloy Fatigue Strength at R.T., MPa 0 0 Creep strength at 150 C and fatigue strength (10 7 cycles) of developed Mg alloy (Mg- 2%Zn-0.8%Ca-2%Mm-0.6%Zr). Dark field image of heat-treated developed alloy observed by TEM.

TiB 2 TiB 2 TiB 2 TiB 2 In- Situ TiB 2 46%TiB 2 1.6345GPa TiB 2 4.5360% 26GPa2 55GPa TiB 2 TiB 2 30%TiB 2 300GPa 1.7 Fe- 13.2%Cr-13.9%Ti-6.

Young's Modulus EGPa 500 400 300 Steel 200 100 E/ρ E 50 TiB2:20vol% 30vol% 46vol% 20 10 ρ = 7.9 ρ = 6.9 ρ = 6.6 ρ = 6.

6 TiB 2 TiB 2 TiB 2 TiB 2 In- Situ TiB 2 46%TiB GPa TiB % 26GPa2 55GPa TiB 2 TiB 2 30%TiB 2 300GPa 1.7 Fe- 13.2%Cr-13.9%Ti-6.4%B (mass%) SUS430Fe-TiFe-B TiAl Ni Ip BSE image of the developed HMS. Young's Modulus EGPa Steel E/ρ E 50 TiB2:20vol% 30vol% 46vol% ρ = 7.9 ρ = 6.9 ρ = 6.6 ρ = Specific Modulus E/ρ, GPa Raw Powders SUS or Fe + Fe-Ti, Fe-B Mixing Compacting Sintering Extrusion Machining 20mm Young's modulus / specific modulus of the developed HMS. Outline of the HMS shaft producing method.

Ip 600 C rpm FOD Mg. Ip 1) : -12(1997)702 2) Nishiyama, Y., Miyashita, T., Isobe, S. and Noda, T. : High Temperature Aluminides and Intermetallics, Ed. by Whang, S. H., Liu, C. T., Pope, D. P. and Stiegler, J.

7 Ip 600 C rpm FOD Mg. Ip 1) : -12(1997)702 2) Nishiyama, Y., Miyashita, T., Isobe, S. and Noda, T. : High Temperature Aluminides and Intermetallics, Ed. by Whang, S. H., Liu, C. T., Pope, D. P. and Stiegler, J. O. (The Minerals, Metals& Materials Soc.), (1990), 557 3) Kim, Y.-W. and Dimiduk, D. M. : Structural Intermetallics 1997, Ed. by Nathal, M. V., Darolia, R., Liu, C. T., Martin, P. L. Miracle, D. B., Wagner. R. and Yamaguchi, M. (The Minerals, Metals & Materials Soc.), (1997), 531 4) Kim, Y.-W. : JOM, -7(1994), 30 Rotating parts made of developed. Resonance frequency of shaft vibration measured by rotating test of turbocharger. Conventional alloy Developed alloy Weight and inertia moment of rotating parts. Wheel Shaft Impellar Nuts Total weight 62 g 29 g 24 g 125 g 10 g (-37%) Inertia moment,ip g/mm (-42%) Rotating parts Conventional Developed Resonance frequency 150,000 rpm 216,000 rpm < 44% up >

5) :, -12(1997), 1365 6) : -6(1998), 504 7)

8 5) :, -12(1997), ) : -6(1998), 504 7) : 93 (1997), 5 8) Emley, E. F. : Principles of Magnesium Technology, (1966), 232, Pergamon Press 9) Handbook of High-Temperature Materials,No.2,Ed. by Samsonov, G.V., (1964), Plenum Press 10) : -8(1998)46 11) : -5(1998), 399

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