Cobalt-chromium alloy vs Ti-6Al-4V
Cobalt-chromium alloy and Ti-6Al-4V are genuine alternatives to one another — a choice somebody actually makes — and differ on 4 measured properties, density most clearly.
Cobalt-chromium alloy vs Ti-6Al-4V
Cobalt-chromium alloy
Harder and stiffer than titanium, and it does not wear — the bearing surface of a joint replacement, and the hot end of a turbine.
Ti-6Al-4V
One alloy is over half of all titanium used — the aerospace workhorse, and the metal a hip replacement is made of.
| Property | Cobalt-chromium alloy | Ti-6Al-4V |
|---|---|---|
| Density | 8.3–9.2 g/cm³ higher | 4.42–4.45 g/cm³ |
| Melting point | 1290–1440 °C | 1604–1660 °C higher |
| Tensile strength These are values for different forms — cast to wrought and worked and annealed to solution-treated and aged — so the numbers describe different substances rather than a difference between them. | 655–1300 MPa | 900–1170 MPa |
| Young's modulus | 210–230 GPa higher | 110–114 GPa |
Choosing between them
Cobalt-chromium alloy is recorded as a substitute for Ti-6Al-4V — stronger.
What it gives up: Roughly twice the stiffness, so it shields bone from load and the bone resorbs — which is why a modern hip uses both alloys rather than choosing between them.
In this application, on the evidence cited above.