Ceramics Laboratory

Department of Materials Science and Engineering

(215) 895-2338 -- Fax (215) 895-6760

Density: 4.5 gm/cc.

Heat Capacity (c_p at R.T.) 588 J/kg.K

Debye Temperature 620 K

Mechanical Properties

Modulus of elasticity: 325 GPa

Shear Modulus: 133 GPa

Poisson ratio: 0.2

Compressive strength: @ RT 1.1 GPa (failure is brittle) @ 1300 °C in air 500 MPa (ductile)

Bend Strength: @ RT 600 MPa (brittle) @ 1300 °C in air 120 MPa (ductile)

Tensile Strength: @ RT » 200 MPa (brittle) @ 1200 °C » 60 MPa ( 5 % strain to failure)

Brittle-to-ductile transition » 1200 °C.

Hardness (Vickers): 4 GPa

Fracture toughness at RT: 7 MPa vm.

This material is very damage tolerant at ambient temperatures and is capable of locally absorbing a lot of energy at room temperature.

Thermal Shock Resistance

This material is not susceptible to thermal shock. Quenching from temperatures as high as 1400 °C, does not affect the bend strength. In other words, the 4-point bend strength before and after quenching are identical.

Oxidation Resistance

At 1000 °C, kw = 2 x 10^-8 kg².m^-4 s^-1 (which is comparable to Cr metal one of tthe most oxidation resistant metals). Activation energy for oxidation » 370 kJ/mol.

Electrical Properties

Conductivity at RT 4.5 x 10⁶ ohm^-1 m-¹. This value is double that of pure Ti metal and roughly two orders of magnitude higher than graphite. Resistance decreases with decreasing temperature. Temperature coefficient of conductivity is » 0.01 °C^-1.

Thermal Conductivity and Expansion

The thermal conductivity was measured at room temperature using a laser flash technique to be 34 W/m K and decreases slightly with temperature.

Thermal expansion coefficient in the 25-1100 °C temperature range is » 9 x 10^-6 °C^-1. The expansion along the a- and c-axes are 8.6 (± 0.1) x 10^-6 K^-1 and 9.7 (± 0.1) x 10^-6 K^-1, respectively.
xyxyxyTemperature dependence of parabolic rate constants

Machinability:

The material is very readily machinable. For example, a 1 cm hole was easily drilled in our sample using a commonly available high speed steel drill bit with no lubrication, and hand tapped to allow us to put a steel screw through it. It can also be sliced with a band saw. Interestingly enough no burrs were evident, but the shavings had a soapy feel to them which leads us to believe this material is probably also self-lubricating.

Abrasive and Sliding Wear

* Counterface (ball) = 440C stainless steel, 9.525 mm diameter; Load = 5 N, sliding speed = 0.1 m/s. Sliding distance = 46.3 m; Wear track diameter = 13-15 mm; Temperature range = 21.6-22.2; Relative range = 53-61 % RH.

** Belt: diamond 220 grit; Load = 10 N; sliding speed = 10 m/s; Test Length: 1 s (10 m sliding distance).

Surface Modification:

One advantage of Ti₃SiC₂ is the fact that it is relatively straightforward to carburize or silicide the surface to enhance both the oxidation resistance and especially the wear properties. Surfaces with a hardness of 25 GPa are easily obtainable. The surface modification is carried out as a last step which would result in very little dimensional changes. xyxyxy

Estimated Cost of Raw Material:

Estimated total cost per pound of raw materials strongly depends on price of Ti powder, but today is of the order of $ 20/pound.

Processing

This material can be processed to full density by sintering of Ti₃SiC₂ powders in Ar atmospheres. We can also thermal spray the Ti₃SiC₂ in air using high velocity oxy-fuel torch.

For more info please contact: Dr. M. W. Barsoum (Click on "Contact Dr. Barsoum" for more details)

Dept. Of Materials Engineering

Drexel University, Phila. PA 19104

Phone: 215 895-2338

barsoumw@drexel.edu