What’s up guys?!?!?!?! It’s Michael with Michael Talks Metals back for video 106. Today we’re going to discuss Case Hardening, yes, again!!!
In the last few weeks we presented some of the methods of case hardening a steel. So what IS Case Hardening of Steel? Good Question – Case Hardening is just a surface layer that is harder and more wear resistant than the core of a part.
For those of you who might have missed the last 3 videos here’s a quick review:
Nitriding forms a thin layer of a hard surface of metallic nitride compounds.
Carburizing raises the carbon content of the surface layer to increase the heat treated hardness.
Carbonitriding increases both the carbon and nitrogen content of the surface layer to boost both hardness and the hardenability of the case.
In all three of these processes we change the chemical composition of the case and perform a heat treatment to achieve the desired properties.
But what if we just selectively heat treat just the surface of the steel to achieve properties?
The heat supplied to the surface needs to raise the temperature high enough to austenitize the steel to the depth to be hardened and then it needs to be cooled rapidly enough to produce martensite.
So what can we use for a heat source?
Blacksmiths would use bellows for air and coal or coke for fuel for hundreds of years.
Next came flame hardening using oxygen and various gas fuels to achieve higher temperatures and faster heat transfer to a part.
When Induction heating coils are introduced , they provide an even more efficient method for heating steel.
And of course today we have technology that can employ lasers or electron beams to provide the energy to heat the steel surface.
Once austenitized, the part needs to be cooled quickly enough to form martensite. That may require application of a coolant. Often the heat flow from the surface into the rest of the part after the heat cycle is sufficient.
The combination of alloy and process to get the required properties gets very complicated in a hurry so we leave the design parameters to the professionals to get right. But its up to us to, never forget to CHECK THE SPECS !!!!!!!
This is Michael with Michael Talks Metal, thanks for watching. Michlin Metals is a supplier and distributor of aerospace metal, check the website www.michlinmetals.com for more info! Still here and haven’t subscribed? Click here, missed last weeks? Click here. This is Michael with Michael Talks Metal. I will see you next Thursday 10am, I’m out!