Xometry offers heat treatment options for machined metals. Heat treatment modifies material hardness or ductility and can also relieve internal stresses. Select heat treatment under Finish in the Edit Configuration tool on your part.
Types of Heat Treatment Finishes
Xometry's drop-down Finish menu includes heat treatments like Annealing, Case Harden, Temper, and Through Harden. These general terms relate to specific treatments, with some examples under each offering.
Annealing
The annealing process is used to improve the properties of metals by slightly altering their microstructure. The process involves heating the metal to a predetermined temperature, for a predetermined amount of time, and then allowing it to cool back down to room temperature. All of the temperatures, times, and cool-down conditions are dependent upon which metal it is as well as the desired outcome. Some examples of common material types and outcomes below:
- Carbon steel - Softens the material, improves machinability, and relaxes internal stresses.
- Aluminum - Improves formability and relieves work hardening leftover from previous processes.
- Chromoly steel - Improves machinability, Reduces hardness, and retains strength.
Annealing Examples
We recommend calling out the specified heat and time schedule in your notes for annealing. Here is an example:
- ANNEAL FOR 2 HOURS AT 300C (572F)
Case Harden
Case hardening is typically utilized for parts that need a hard surface while retaining a softer core for better overall performance. This process is mainly utilized for steel parts. The parts are heated up to a preset temperature, usually higher than that used for annealing, and then rapidly cooled using water, oil, or some other medium. See some examples below:
- Low-carbon steels—Parts are first carburized to increase their carbon content. After the part absorbs enough carbon content, it is sent through the heat treatment process to achieve a case hardening.
- Alloy steels—Since these materials are a combination of others, they typically utilize a process called nitriding to achieve a case hardening condition. This gives the parts a good balance of strength, toughness, and wear resistance.
- Stainless steels—Like alloys, stainless steels typically undergo the nitriding process. Nitriding does not affect the corrosion resistance of stainless steel, so it’s the most utilized method to achieve a case-hardened condition.
Case Hardening Examples
We recommend calling out the specified case depth and Rockwell hardness in your notes for case hardening. Here are examples:
- CARBURIZE .015" TO .020" DEEP. 55-60 ROCKWELL "C"
- CARBURIE & HARDEN .030" DEEP TO Rc 60-62.
- CARBURIZE TO Rc 48 to 53. FINAL EFFECTIVE CASE DEPTH .3" to .6"
Temper
Tempering is another process that steel parts can also utilize. Tempering can change the ductility, hardness, and toughness of parts after they’ve been quenched during the heat treatment process. As a side effect of hardening, the parts can become brittle. The tempering process is one way to toughen the parts to better suit their application. In addition to steel, aluminum can also go through a tempering process. It is also referred to as artificial aging but is utilized to increase strength after quenching.
Temper Examples
We recommend calling out a technical specification, desired hardness outcome, or timeframe and temperature instructions on your notes for tempering. Here is an example:
- MATERIAL DESCRIPTION: CDA 360, TEMPER HALF HARDENED PER ASTM B16
Through Harden
As its name suggests, this process is utilized to harden a part throughout its entirety, not just on its surface. The process follows the same workflow as case hardening, but it is done on higher carbon content materials. The end result is a part that has the same hardness and properties on the outside as on the inside. More often than not, the parts also go through the tempering process to reduce brittleness after they are hardened. This process is exclusively for steel-based materials and their alloys. It is important to note that steels with less than 0.3% carbon content have no way of becoming hardened. The starting material must have a carbon content higher than 0.3%. Some common steel types are below:
- Carbon steels - 1045, 1050, 1095
- Alloy steels - 4140, 4340, 8620
- Tool steels - A2, O1, D2
Through Harden Examples
We recommend calling out a desired hardness outcome on your notes for thorough hardening. Here are examples:
- HEAT TREAT TO 38-43 HRC PER SAE AMS2759
- HEAT TREAT TO ROCKWELL 60HRC, HEAT TREAT AT 1850-1950F, SOAK AT HEAT, OIL QUENCH, TEMPER AT 300-400F FOR 1 HOUR, AIR COOL
- MAKE FROM 300M ALLOY STEEL, HEAT TREATED TO HRC 53-58 PER AMS 2759/2 TYPE 3
FAQ
- How is heat treatment verified or inspected?
- When a finish is selected on the quoting engine, Xometry will automatically apply a Finishing Certification requirement to be delivered with your part(s). This will confirm that the parts were finished and tested to the required specifications.
- Do I need to call out heat treatment on pre-treated metals like 17-4PH SS H900?
- No, this would be covered in the Material selection, not the Finish selection.
- Should I select just one or both options if my part needs heat treatment AND tempering?
- Because each thermal processing has its own unique steps, we recommend using the
Add function on the Finish drop-down to select each unique heat treatment required.
