Choosing the Right Heat Treatment Process: A Commercial Buyer’s Guide

Key Takeaways:

• Heat treatment can significantly enhance the durability and performance of your metals
• Selecting the correct form of heat treatment ensures greater success
• In the commercial industry, there isn’t one best way to heat treat metals
• Our Bedford facility works hard to ensure businesses in the commercial industry get the quality products they need

Why Heat Treatment?

Investing in the right heat treatment is one of the most effective ways to elevate the performance and reliability of your metal components. This critical manufacturing step delivers several tangible benefits that directly contribute to product quality and your bottom line:

1. Enhances Hardness and Strength for Durability

A primary goal is often to enhance hardness and tensile strength by refining the metal's internal grain structure. In commercial settings, this translates to stronger gears capable of greater torque, more durable tooling that retains sharpness longer, and structural components designed to withstand extreme forces without failure.

2. Improves Wear Resistance for Longevity

Constant abrasive and adhesive wear affects components that rub, slide, or roll against each other. Heat treatment significantly enhances the surface's resistance to this friction, thereby extending the operational life of crucial parts such as bearings, camshafts, and cutting blades. This, in turn, leads to reduced maintenance and replacement frequency.

3. Increases Toughness to Prevent Fractures

While hardness helps a part resist deformation, toughness is what allows it to absorb impact and energy without fracturing. Some heat treatment processes are specifically designed to impart toughness, which is vital for components like automotive suspension parts, high-impact tooling, and landing gear that must endure sudden shocks as part of their normal function.

4. Relieves Internal Stresses to Minimize Distortion

Manufacturing processes like machining, welding, and forming can leave residual internal stresses locked within a component. These hidden stresses can lead to warping, distortion, or even cracking long after the part has been put into service. A stress-relieving heat treatment cycle neutralizes these internal forces, ensuring the part remains dimensionally stable and reliable throughout its lifecycle.

Core Considerations for Heat Treat Process Selection

Making the right heat treat process selection is not a one-size-fits-all decision. It's a careful calculation involving three critical variables: the material you're starting with, the performance you need, and the physical nature of the part itself. Getting any one of these wrong can compromise the final component.

So let’s take a look at each.

The Material:

The single most important factor in any heat treatment plan is the material itself. The alloy's chemical makeup dictates its potential—what it can and cannot become through thermal processing. Carbon is the primary hardening element in steel; the higher the carbon content, the harder the steel can become.

Because of this, different hardened steel alloys respond uniquely to treatment. For example:

• A low-carbon steel like 8620 is ideal for carburizing, where carbon is diffused into the surface to create a hard case while the core remains soft and ductile
• A medium-carbon steel like 4140 is an excellent candidate for through hardening (quenching and tempering) to achieve a uniform, high-strength microstructure
• A high-carbon tool steel like D2 can be hardened to an exceptional degree to provide superior wear resistance for cutting and forming applications

The Performance Needed:

With a clear understanding of your material's potential, the next question is: "What does this part need to do?" The intended application directly informs the desired mechanical properties, which in turn points toward the optimal heat treatment. Consider these common trade-offs:

• Surface Hardness vs. Core Toughness: Does the component need to withstand surface wear while also absorbing impact? A gear is a perfect example. It requires an extremely hard, wear-resistant surface to handle teeth meshing, but it also needs a softer, tougher core to prevent the teeth from snapping off under load. This requirement points directly to a case hardening process like carburizing.
• Wear and Abrasion Resistance: If a component's primary challenge is friction, the focus shifts entirely to maximizing surface hardness and durability. For applications like industrial blades or tooling, processes that create a hard, stable surface are prioritized.
• Ductility and Malleability: Sometimes, a part needs to be soft and easy to form or machine. In these cases, annealing is used before the final hardening process. It resets the metal's internal structure, making it more workable for subsequent manufacturing steps.

The Physical Nature of the Part:

Part characteristics pose challenges for uniform heat treatment without distortion or cracking.

Complex shapes and thin sections are prone to stress concentrations during quenching, leading to warping or cracking due to uneven cooling. Part mass and volume dictate cooling rates, affecting microstructure and hardness. 

The quenching medium must be chosen to ensure consistent cooling throughout. An experienced partner assesses geometry and mass to minimize risks, ensuring strong, dimensionally accurate products. For example, oil quenching provides a thorough quench for materials like 4140 and 4340. However, say the 4340 part, which is crack-sensitive, has sharp edges or abrupt changes in cross-section, a quenchant like polymer or salt may be a better alternative to minimize the risk of quench cracking. Ensuring your heat treat provider is aware of these risks and options is critical to the success of your part(s).

A Buyer’s Overview of Common Commercial Heat Treatments

When it comes to heat treatment in the commercial industry, there are a few options out there. Whether each one is the right one for you depends on what your needs are. We have explored the options below so you can make a more informed decision for your business.

Through Hardening (Quench & Temper): 

This is a primary process used to achieve uniform strength and hardness throughout a component. Most steels like 4140, 4340, D6AC, 300M, and 4130 tend to benefit from a quench and temper. Bedford offers oil, salt (marquench), and polymer quenchants to support through hardening.

Austempering:

One of Bedford’s core competencies, Austempering increases ductility, toughness, and wear resistance of metals. It also achieves a superior strength-to-weight ratio than an annealed part would. This heat treat practice requires a salt quench with a higher temperature than a standard marquench would provide. Bedford primarily utilizes austempering for the trucking, train, oil and gas, and agricultural industries, which require high volumes and fast turnaround shipments.

Case Hardening (Carburizing):

This method creates a very hard, wear-resistant outer surface while keeping the inner core of the metal softer and tougher. It's ideal for parts like gears and bearings that need to withstand surface friction but also absorb impact.

Annealing:

This process is used to soften metal, making it easier to machine or form. It essentially "resets" the material before it undergoes its final treatment.

Stress Relieving: 

Used to reduce the internal stresses that can build up in a part from manufacturing processes like welding or machining, which helps prevent distortion or cracking later on.

Choosing the Right Partner

Once you know which heat treatment process is the one for you, your next step will be finding the right heat treatment provider. Luckily, Rex Heat Treat has many options available at a couple of locations. Our Bedford, PA, location is specifically geared towards the needs of the commercial buyer. Bedford heat treats oil and gas, trucking, military and defense, agriculture, construction and drilling, trains and railways, and more commercial industries.

Bedford utilizes efficiency and best quality practices to service high volume and quick turnaround requests. We provide services including, but not limited to, austempering, austenitizing, marquenching, carburizing, masking, and age hardening. 

This location in central Pennsylvania has served critical industry partners for 25 years, and our 80,000 sq ft facility offers flexible, full-service operations 24/7.

If you are worried about the quality, rest assured that Bedford has you covered. While not Nadcap-approved, Rex Heat Treat Bedford frequently heat treats in accordance with Aerospace standards like AMS 2759/1, AMS 2759/2, AMS 2759/3, and more specifications. Additionally, our Bedford facility offers decarburization testing, microstructure analysis, tensile testing, failure analyses, and additional lab services to ensure customers receive consistent, quality materials.

If you are interested in any of our services, please contact us today! Our experts are standing by to assist you.