Material Development

Impervium? Eternium? What do you call a nearly unbreakable metal? Dr. Richard Waterstrat has been pondering that question ever since he invented an alloy that is nearly impervious to wear. Several years ago at the National Institute for Standards and Technology, Dr. Waterstrat was developing a metal for use in artificial hips and knees. Because the alloy would be implanted into the human body, it needed to be both nontoxic and crack-resistant. He made one alloy by mixing three metals— zirconium, palladium, and ruthenium. The alloy seemed promising, so Dr. Waterstrat sent it down to the machine shop to prepare a sample for testing. Soon after, Dr. Waterstrat received a call from a worker in the shop who reported that he was unable to cut the alloy in a lathe, using conventional meth- methods. At first, Dr. Waterstrat thought that the metal might simply be too hard to cut. But closer examination revealed that a very thin fibrous layer had formed wherever force had been applied to the metal. The crystalline structure of the alloy's surface had changed in response to the force to prevent new damage. The metal had actually "healed itself." "The new crystals are harder and stronger than the original crystals," Dr. Waterstrat explained, "and that reinforces or 'heals' the defects that form as a result of the applied stress, making the material, in fact, stronger than it was to begin with. So the unusual wear-resistance is due to the fact that the metal is continually forming crystals under stress to resist further wear." Dr. Waterstrat's alloy not only was resistant to cracking but also was found to be nearly impervious to wear. He submitted the alloy to a test to measure its wear-resistance, its ability to withstand intense wear over a long period of time. After a pin was rubbed against the metal for 5 million cycles, the alloy showed practically no wear. Artificial joints are constantly subjected to wear, so it seemed that Dr. Waterstrat had finally found his ideal metal. While the alloy is still being perfected for use in joint replacements, there are other applications for which it might be used. Any piece of metal that is subject to extreme wear, such as drill bits, bearings in machinery, or needles in sewing machines, could be coated with the wonder metal. The alloy also seems to be corrosion-resistant, suggesting that it could be used as the metal contact in an electric circuit, a part that is constantly subjected to high wear and corrosion.

As engineer we know high wear resistant contradict with high toughness. Research for this characteristic also demand. SS400 is a material from steel grade that have tensile strength 41kg/mm2 and carbon contain below standard of hardenability. But recently my instructor develop some technic to improve SS400 because is cheap yet we can get the benefit for it strength.

After some experiment SS400 can achieve surface hardness 70HRc and the core still have toughness characteristic. That can be apply for spring steel or even cutting tool material. He use carbon from animal bone for medium for carburizing process.

As can see on the part below, all are made from low carbon steel SS400. Cutting Tool, spring part and machinery gear application.