Nitriding vs. Induction Hardening for Pins

Nitriding vs. Induction Hardening for Pins

In the world of heavy equipment and machinery, heat treatments play a critical role in extending the life cycle and performance of components like attachment pins and bushings. At Nitrera Technologies, we’ve processed a wide range of parts that traditionally weren’t nitrided, often at the request of our customers. In nearly every case, switching to nitriding has delivered superior results. Beyond pins and bushings, nitriding has successfully replaced treatments such as induction hardening, chrome plating, nickel plating, black oxide, phosphate coatings, boron-nitride spray coatings, ceramic coatings, paint, and Cerakote. In some cases, nitriding lower-cost materials like carbon steel has eliminated the need for more expensive options, such as stainless steel in corrosive environments.

We’ve observed growing interest in using nitriding as a replacement for induction hardening, particularly for heavy equipment attachment pins and bushings. Nitrera has been nitriding these components for numerous customers over the years, with one client fully transitioning thousands of pins and bushings to nitriding 8 years ago—and reporting outstanding success. To provide deeper insights, we gathered feedback from customers who have made this switch, asking a standardized set of 17 questions. Their responses, combined with our technical expertise in liquid nitrocarburizing highlight why nitriding is often the better choice.

Note: In this article, bushings are mentioned along side pins, but we do not mean to imply that bushings are traditionally induction hardened (which they are not).

Customer Insights: Nitriding in Action

Our customer feedback underscores the real-world advantages of nitriding over induction hardening of pins. Here’s a summary of key responses:

• Longevity of Nitrided Pins in Regular Bushings: One customer reported that nitrided pins last approximately twice as long as induction-hardened pins. Others noted no returns or negative reports, though feedback loops can take years due to the long service life of these components.‍
• Longevity of Nitrided Pins in Nitrided Bushings: When paired with nitrided bushings, pins can last up to four times longer than induction-hardened alternatives, according to one respondent. Again, no negative feedback was reported.
• Materials Used: All customers use 4140 steel for both nitriding and induction hardening, making direct comparisons straightforward.
• Corrosion Resistance: Nitriding dramatically boosts corrosion resistance. One customer described nitrided pins as “orders of magnitude better” than induction-hardened ones, especially for attachments exposed to water. This aligns with our testing, where nitrided carbon and low-alloy steels withstand up to 400 hours in ASTM B117 salt spray tests—far surpassing untreated or induction-hardened parts.
• Storage and Rust Prevention: Pins stored outdoors or in humid conditions benefit greatly from nitriding’s corrosion resistance. Induction-hardened pins often rust and require sanding or lathe work before use, while nitrided pins remain rust-free—a “welcomed bonus” per customer reports.
• Dimensional Stability: Nitriding causes minimal growth, about 0.0001" to 0.0004" per surface (or roughly 0.0005" on diameter). In contrast, induction hardening can lead to 0.001" or more growth, depending on pin diameter and case depth, potentially requiring additional machining.
• Cost of Nitrided Bushings: Customers find nitrided bushings comparable in price to alternatives, but with far superior quality and durability.
• Additional Advantages of Nitriding Pins:
  
  • Aesthetic appeal: A sleek black finish with no discoloration, giving a “finished” look.
  • Durability during installation and use: Nitrided pins resist scuffing when hammered into tight bushings, unlike induction-hardened ones.
  • No need for center holes: Eliminates fixturing requirements common in induction hardening.
  • Tight tolerances: Ideal for bearing fitment due to nitriding’s stability.
  • Rust resistance in storage and transport: Pins withstand rain and weather without issue.
  • No warping: Longer or thinner pins avoid distortion seen with induction.
  • Built-in lubricity: The ceramic-like iron-nitride layer provides friction reduction, beneficial if greasing is overlooked. One example: Electrical line worker boom lift trucks specify nitrided pins for fiber bushings, where greasing isn’t possible due to electrical conductivity needs.
• Disadvantages of Nitriding Pins: Remarkably, customers reported no disadvantages based on the questions asked.
• Cost Comparison: Pricing is comparable between nitriding and induction hardening, varying by pin size and volume. Nitriding’s long-term savings in maintenance and replacements tip the scale in favor of nitriding.

These insights reflect nitriding’s versatility, drawn from our experience and customer experiences across industries.

Nitriding Wins: A Comparative Overview

Nitriding excels in several areas over induction hardening, particularly for pins and bushings in heavy equipment. While induction hardening provides a deeper case for potential strength against bending or shearing (though the difference is often negligible or not required), nitriding’s advantages are clear in durability, maintenance, and environmental performance.

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These benefits stem from nitriding’s unique process, which diffuses nitrogen (and carbon in nitrocarburizing) into the surface at lower temperatures (around 1055°F), maintaining the material’s ferritic phase and minimizing distortion.

Disadvantages: Are there any disadvantages to nitriding as compared to induction hardening? Yes, there are potentially a few:

1. While induction hardening provides a deeper case for potential strength against bending or shearing, the difference is often negligible or not required. It really depends on the application, but to date we have not had a failure owing to nitriding in place of induction hardening.
2. Nitriding is a full coverage process. Selective treatment (extremely rarely required), and masking are not among the available options. If selective treatment is required, you may wish to leave material on the features you do not want nitrided and then finish machine them after nitriding.

Endorsements from Industry Leaders

Our customers’ success stories speak volumes:

• Ed Lingel, President, Daequip Premium Attachments Ltd. “Nitriding our pins and bushings has increased performance and with tight tolerances and minimal distortion making it perfect for our precision attachment pins offering better wear resistance and lubricity for a longer life“
• Larry Pearson, President, Dynamic Link Hydraulics & Machining Ltd. “The sleek black finish of nitrided parts enhances our product's look without sacrificing performance”
• Henry Hansman, President, IOS Enterprises. "Nitriding our pins and bushings has 2-4x their lifespan compared to induction hardening, giving us a competitive edge"

Technical Deep Dive: How Nitriding Works

Nitriding is a case-hardening process—not a coating—that diffuses nitrogen into the metal surface to form iron-nitride compounds. Unlike carburizing, it focuses on nitrogen for enhanced hardness, wear resistance, and lubricity. The process temperature of 1055°F is low enough to avoid phase changes, acting like stress relief (similar to 1000-1200°F treatments). For 4140 steel, the total case depth is typically 0.008"-0.012" with standard soak times, and effective case depth (to 50 HRC) is 0.002"-0.005".

Key technical notes:

• Core Hardness Impact: 4140HTSR is not further tempered by the nitriding process. Quench hardened 4140 tempers back to 36-37 HRC core hardness (if previously higher), but nitriding over induction hardening is possible (though not always ideal).
• Welding Compatibility: Parts can be welded before or after; remove 0.010"-0.020" of material if welding after nitriding, or just weld before nitriding. Bonus: Nitriding can double as stress relief for weldments.
• Painting: Possible, but notify us to skip oilingif yo plan to paint after nitriding. Bonus: Nitriding’s black corrosion resistant finish may make painting unnecessary.
• Process Variants: Choose Q for basic hardening, QP for polished finishes, or QPQ for maximum corrosion resistance—especially for harsh environments.

Nitriding reduces wear and galling through increased hardness and lower friction, often eliminating the need for lubrication. It’s a safety net for lube failures, as seen in engine crankshafts.

Why Choose Nitriding for Your Pins and Bushings?

From extended lifespan and corrosion resistance to minimal distortion, nitriding offers a compelling alternative to induction hardening for heavy equipment components. We’ve compiled extensive research, including 35 documented benefits of nitriding, from enhanced fatigue strength to resistance against fretting and abrasive wear.

For more details or to discuss your specific needs, contact us at [email protected]. We’re here to help optimize your parts for peak performance.