This dataset tracks 50 patent families filed between 2015 and mid-2026 that combine metallography or EBSD-based microstructure analysis with sample preparation, grain size measurement, phase quantification, texture analysis or automated imaging, all classified under G01N1, G01N23 or G01N33. The true figure for very recent years is understated because publication typically lags filing by about 18 months. Anyone scoping a full freedom-to-operate search should treat 50 as a floor for this specific search definition, not a ceiling, since broader IPC or keyword choices would pull in more records.

Ownership in this dataset is fragmented rather than concentrated: only four co-assignee pairs exist across all 50 families, and the most visible names, including rail rolling-stock, steel and specialty-alloy manufacturers, show zero filings in the latest tracked year. This is a field of largely independent, single-assignee filers rather than one dominated by a small group of repeat filers. A ranking table sits alongside this analysis showing the specific assignees by family count.

Filing activity peaked at 7 families in 2021 and had fallen back to 3 by the 2022 midpoint, with no clear recovery in the years since. Part of that apparent drop is a publication-lag artifact, since the most recent one to two years are always undercounted at the time of any snapshot. But the multi-year decline from the 2021 peak is real enough that it likely also reflects the core sample-preparation and imaging techniques being already well claimed, pushing new filers toward narrower process variations rather than broad new claims.

GB2551868A claims a specific two-step colour metallography process for wrought aluminium alloy welded joints: an acid pre-etch at a defined temperature range and immersion time using a solution with specific ion concentrations, followed by a short Weck-reagent immersion step. Because the claims are tied to numerically bounded process parameters rather than the general concept of colour etching, work using different temperature, timing or reagent-concentration ranges, or applied to non-aluminium alloys or non-welded-joint samples, is likely to sit outside its claim scope. Anyone using acid pre-etch plus Weck-reagent colouring on aluminium welds specifically should review the granted claims in detail rather than relying on this summary.

The lightest overlap with the core G01N filing cluster shows up in automated EBSD grain-boundary segmentation, machine-vision-based phase quantification, and in-situ texture analysis performed during processing rather than after the fact, alongside sample-preparation etchants tuned for polymer-composite substrates and multi-material colour metallography. These branches show secondary-classification activity in G06T and G06K but are not the center of gravity of the filed claims. A first claim in these areas would typically need to tie a specific imaging or segmentation algorithm to a defined material system or process step, since broad claims on automated grain analysis generally risk overlap with existing sample-preparation and imaging prior art.