Avoiding Eutectic Reactions

A Chart of Maximum Temperatures at Which Materials Are Compatible in Vacuum:

Metallurgy, or the science concerned with the physical and chemical properties of metals, is one that many people find intimidating due to its very technical nature. As an operator of heat treatment equipment, you may think, “I’ll let the scientists handle that,” or “metallurgy doesn’t apply to me.”

But the truth is, it does. Many of the decisions you make regarding your equipment and processes are based on metallurgy – even if you don’t realize it. For example, you probably know that each metal has a melting point. Molybdenum, commonly referred to as moly, has a melting point of 4,753 ºF (2,623 ºC), while carbon (graphite) has a melting point of 6,422 ºF (3,550 ºC). Their ability to withstand some of the highest temperatures of any elements makes them great choices for hot zone construction.

Did you know, however, that the melting point of some metals can actually change when they come into contact with other metals? If these metals come in contact with each other at or above certain temperatures, they will melt.

Eutectic Reactions
The results of a eutectic reaction in the hot zone of a furnace. Avoid this by referencing the chart of maximum temperatures at which materials are compatible in vacuum.

This is known as a eutectic reaction, and it can not only cause damage to the parts in your load, but also to your hot zone and, in some cases, your entire furnace. This is why it is critical to not only know a metal’s melting point, but also the maximum temperature at which certain materials are compatible with others while in vacuum.

Remember the melting point of moly? It’s 4,753 ºF (2,623 ºC). However, if moly comes into contact with titanium, which has a melting point of 3,034 ºF (1,668 ºC), the maximum temperature at which these two materials are compatible in vacuum is only 2,300 ºF (1,260 ºC). If they come in contact at or above 2,300 ºF (1,260 ºC), they would cause a eutectic reaction in the furnace.

Click here to view a complete chart of the maximum temperatures at which materials are compatible in vacuum.

There are some preventative steps that can be taken to prevent these reactions if you are working with reactive materials above the maximum temperatures. If your process requires such steps, contact Ipsen’s Technical Support Team at 1-844-Go-Ipsen for the recommended steps.

Several online resources provide slightly different melting point temperatures for individual elements. We referenced the Los Alamos National Laboratory’s periodic table for the information provided in this post.