Gear Heat Treatment Patents: Leaders, Trends & White Space 2026
- Concentrated at the top. the ranked leader alone holds 11 of 51 records, and the top 5 combined account for 56.9% of all 51 records in scope.
- Heat treatment chemistry dominates the claim map. C21D, C23C and C22C each cover roughly two in five of the 51 records, while gearing-specific F16H sits at just 13.7%.
- Filing activity has gone quiet since its 2020 peak. the field peaked at 6 records in 2020, and the documented 2021→2024 span shows a full -100% falloff to zero complete filings.
Filing growth compares 2021 (1 records) with 2024 (0) — a three-year span. 2024 is the most recent year we treat as complete: publication lags filing by roughly 18 months, so 2025 onwards are still filling in and any growth rate that ends there would understate the field. Top-5 share is the combined record count of the five largest assignees divided by all 51 records in scope (CR5), not by the ranked leaders only.
What this landscape covers
This dataset tracks 51 published patent families filed against a search built around gear heat treatment, case carburizing and distortion control, cross-referenced against process terms like low pressure carburizing, press quenching, retained austenite and shot peening. The scope runs from 2015 through the 2026-07-31 cut-off, capturing both the metallurgy side (case depth uniformity, intergranular oxidation control) and the mechanical distortion-control side of gear manufacturing.
Because publication lags filing by roughly 18 months, the most recent one to two years in any trend understate real filing activity — treat 2025 and 2026 as still filling in, not as a genuine drop-off.
Filing trend and technology composition
Filing volume and IPC composition across the 51 records in scope, drawn directly from the underlying search.
Filing trend, 2015–2026
Activity peaked at 6 records in 2020. The documented growth figure for 2021→2024 is -100%, a complete span end to end rather than a single bad year — but with 2024 as the last complete year and everything after it still lagging into publication, this reads as a lull rather than a verdict on the technology's future.
IPC subclass composition
C21D (heat treatment of metals) leads at 43.1% of the 51 records, closely followed by C23C (coating and surface deposition) at 41.2% and C22C (alloys) at 39.2%. Mechanical subclasses trail well behind: F16C (shafts, bearings and couplings) at 17.6% and F16H (gearing and transmissions) itself at only 13.7%, with powder metallurgy, non-ferrous treatment and forging each under 4%. Records can carry multiple classes, so these shares sum to more than 100%.
Shares are the percentage of the 51 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
Go deeper on Gear Heat Treatment and Distortion Control with Eureka
This page is one run against one query. Ask Eureka your own question about gear heat treatment and distortion control and every answer comes back with the patent numbers behind it.
Try EurekaThe most-cited records in this space
US3891474A — Method for the case carburizing of steel
In the case carburizing of low carbon (<0.4%C) steels, the hardness of the case and toughness of the core are both improved by following a prescribed heat-treating sequence. After the article is carburized in contact with a carbon containing substance, it is quenched to below about 900 degrees F and maintained within the bainite region for a time sufficient to transform retained austenite. The article is then austenitized by rapidly heating to a temperature above the A3 of the core, after which it is quenched and tempered in a conventional manner.Filed by USX Corporation, dated 1975-06-24 — one of the oldest and most-cited records in this dataset at 39 citations.
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | US5683183A | Spindle device and bearing device therefor | 86 |
| 2 | US3891474A | Method for the case carburizing of steel | 39 |
| 3 | US3737204A | Extended life bearing | 34 |
| 4 | US20160298203A1 | High fatigue strength components requiring areas of high hardness | 27 |
| 5 | US5660647A | Rolling bearing with improved wear resistance | 27 |
| 6 | US20020124911A1 | Low carbon, low chromium carburizing high speed steels | 20 |
| 7 | US20070221006A1 | Variable case depth powder metal gear and method thereof | 19 |
| 8 | US6702981B2 | Low-carbon, low-chromium carburizing high speed steels | 19 |
| 9 | GB2292389A | Rolling bearing | 19 |
| 10 | WO2015199599A1 | Method for surface hardening a metal component | 13 |
Citation counts inside this corpus skew toward older filings that have had more time to accumulate citations — read them as a signal of influence, not of current relevance.
Each row carries its publication number; clicking a row searches Eureka by that number.
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Three patterns stand out once the records are broken down by assignee, class and filing year.
A narrow leadership group, then a long tail
The ranked leader alone accounts for 11 of the 51 records in scope. The top 5 combined reach 56.9% of all 51 records, and the top 10 reach 82.4% — leaving 12 of the 22 ranked companies with only single-digit filing counts.
Metallurgy claims outnumber gearing-specific claims
Heat treatment (C21D), coatings (C23C) and alloy composition (C22C) each sit near or above 40% of the 51 records, while gearing-and-transmission-specific claims under F16H cover only 13.7%. Most of the documented claim space describes the process and material, not the gear geometry itself.
Activity has cooled since the 2020 peak
Filings peaked at 6 records in 2020. The documented span from 2021 to 2024 shows a full -100% falloff to zero complete filings, though 2025-2026 figures are still filling in given the roughly 18-month publication lag.
Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to gear heat treatment and distortion control, with the prior art for and against each one.
Who is filing, and where the gaps sit
Filing activity concentrates among a small group of established bearing, automotive and heat-treatment specialists, with most other assignees appearing once or twice.
A single company leads the ranked field
The top-ranked assignee holds 11 of the 51 records in scope, more than double the count at fifth place (4 records), underlining how tightly the core carburizing and press-quenching claims are held.
A thinning mid-tier before the long tail begins
Fifth place holds 4 records and tenth place holds 2, meaning the top 10 together reach 82.4% of the 51 records — the remaining 12 ranked companies split the rest.
Momentum has flattened across the leading names
None of the leading assignees tracked for recent-year momentum show filings in the latest year, consistent with the broader -100% falloff documented for 2021 to 2024 and the publication lag affecting the newest years.
| Assignee | Recent year | YoY |
|---|---|---|
| The Timken Company | 0 | — |
| Metal Improvement Co LLC | 0 | — |
| NSK Ltd. | 0 | — |
| AB SKF | 0 | — |
| ORIENTAL ENJINIARINGU | 0 | — |
| Public Interest Inc. Association Research Institute for Applied Science | 0 | — |
| Neturen Co., Ltd. | 0 | — |
| Mazda Motor Corporation | 0 | — |
Where to take this next
The landscape points to specific next steps depending on whether the goal is freedom-to-operate, licensing, or R&D scoping.
Map claim boundaries around the leader's 11 records
With one assignee holding more than a fifth of all 51 records, a freedom-to-operate review should start by pulling that portfolio's independent claims before scoping any new carburizing or press-quenching process.
Explore the leader's portfolio in EurekaTest the under-claimed branches for a first-filer position
F16H-specific gearing claims sit at only 13.7% of records against 40%+ for the underlying metallurgy — a gap worth probing before assuming the geometry side is already occupied.
Run a white-space search in EurekaWatch for the 2025-2026 filing wave to surface
The apparent falloff after 2020 partly reflects publication lag; re-checking assignee momentum once 2025-2026 filings finish publishing will clarify whether activity has genuinely paused.
Set an alert in EurekaCommon questions about this landscape
Within the 51 records in scope, one assignee leads with 11 records, well ahead of the rest of the field. The top 5 assignees combined hold 56.9% of all 51 records, and the top 10 hold 82.4%, so filing activity is concentrated among a handful of established bearing, automotive and heat-treatment companies. Beyond the top 10, the remaining ranked companies each hold only a few records, forming a long tail of narrower or more experimental filings.
Case depth uniformity governs how evenly the hardened surface layer forms during carburizing, and uneven case depth is a major driver of distortion during quenching. This dataset groups case depth uniformity together with press quenching and retained austenite control because process patents in this space typically address all three together — controlling the carburizing atmosphere and quench sequence to limit both hardness variation and geometric distortion in the finished gear.
The documented data shows filings peaking at 6 records in 2020, followed by a -100% falloff from 2021 to 2024. That said, publication lags filing by roughly 18 months, so the 2025 and 2026 figures in this dataset are still filling in and should not yet be read as a genuine slowdown. A clearer picture will emerge once those years finish publishing.
C21D (heat treatment of metals) is the largest class at 43.1% of the 51 records, followed closely by C23C (coating and surface deposition) at 41.2% and C22C (alloys) at 39.2%. Gearing-specific claims under F16H cover only 13.7% of records, and mechanical subclasses like F16C (shafts, bearings and couplings) sit at 17.6% — indicating that most patent activity centres on the metallurgical process rather than gear geometry itself.
US3891474A, filed by USX Corporation, claims a specific case-carburizing sequence for low-carbon steels: carburizing followed by quenching into the bainite region to transform retained austenite, then re-austenitizing above the core's A3 temperature before a final quench and temper. Anyone using a similar multi-step reheat-and-requench sequence to manage retained austenite in low-carbon carburized steel should review this claim carefully, since it is one of the most-cited records in this dataset at 39 citations. Alternative approaches that skip the intermediate bainite hold, or that rely on low-pressure carburizing with different retained-austenite control, sit outside its literal claim language.
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Disclaimer. This page is generated from Patsnap Eureka data drawn from a limited snapshot of global patent and scientific-literature records, and is provided for general information and reference only.
Patent data carries inherent limitations: recent filings (typically the most recent 18–24 months) are under-counted due to standard publication lag; counts may be reported at either a patent-family or a patent-record basis and are not always directly comparable; classification, applicant-name, and citation data may contain errors, duplicates, or omissions; and the underlying search query defines and constrains the scope shown. As a result, the analysis may be incomplete or inaccurate and may not reflect the full technology landscape.
Nothing on this page constitutes an exhaustive prior-art, novelty, freedom-to-operate, or validity search, nor does it constitute legal, financial, investment, or professional advice, and it should not be relied upon as such. Any patent, commercial, or strategic decision should be verified independently and reviewed with qualified patent, legal, and domain professionals. Patsnap makes no warranties, express or implied, as to the accuracy, completeness, or fitness for any particular purpose of the information presented.
Machine translation. Assignee and organisation names originally recorded in Chinese, Japanese or Korean have been rendered into English by an AI translation step so that the tables stay readable. These renderings are best-effort and may not match a company’s registered English name; the original name is what the underlying patent record carries, and it is what any Eureka query launched from this page uses.