A cross-reference chart tells you which grade is nearest, not which one will work, and the difference between those two statements is where most substitution problems start. The chart compresses a set of properties into a position, and the position can be reached by more than one combination of grain size and binder content.
This guide works through what the classes actually describe, how to read a hardness and wear table without over-reading it, why cross-references are approximate by construction, how coatings change the picture on a bonded insert, and what to do before a substitution is committed to a season.
Carbide insert grade chart: what the classes actually describe
A grade is a combination, not a single value.
What a grade designation describes, whether or not the supplier says so, is a combination of four things: the grain size of the carbide, the proportion of binder metal, the measured hardness, and the measured transverse rupture strength.
Two suppliers can reach the same hardness position with different grain and binder combinations, which is why the designation alone cannot be transferred between them.
The application classes that appear on many charts originate in cutting-tool practice, where inserts are indexed and disposed of rather than bonded to steel. They are widely borrowed for wear parts because they give a convenient shorthand, but they were not devised to describe an insert that has to survive a brazing cycle and then hold a plow edge against impact. Reading them as a wear-part specification is the first mistake a cross-reference invites.
What can be compared properly between suppliers is the underlying set of values. Grain size classification and metallographic measurement conventions are published by ISO, and the test methods for hardness and transverse rupture strength by ASTM International. Asking two suppliers for the same four values is a more useful exercise than comparing their codes.
Hardness, strength and wear tables
A grade table gives a position along a trade-off, and each column describes a different property rather than a better or worse one. Reading the table properly means knowing which column the application actually depends on.
| Column | What it describes | What it does not tell you |
|---|---|---|
| Hardness (HRA) | Resistance to indentation, and a proxy for abrasive wear resistance | Whether the insert will survive an impact on the same route |
| Transverse rupture strength | Bending load carried before fracture | Behaviour under repeated impact or thermal cycling |
| Grain size class | Coarseness of the carbide structure and the flaw size behind it | How the material was sintered, which decides whether the class was achieved |
| Binder content | Proportion of the tough phase available | Corrosion behaviour in a salty environment |
| Application class | A shorthand grouping from cutting-tool practice | Anything specific about a brazed or mechanically fixed wear part |
The first two rows are the ones that move together and are usually quoted together. The last row is the one that gets substituted for a specification when a buyer has nothing else to hand, and it is the one least suited to the job.
Why cross-references are approximate
A cross-reference is built by aligning grades on one or two properties, which means it is only as good as the properties chosen. Where two suppliers report hardness against different test methods, or report a strength figure from a specimen of different geometry, the alignment is approximate before any material difference is considered.
Three further sources of difference sit outside the table entirely. Production route changes whether a fine-grained powder stays fine through sintering. Surface condition after finishing changes how the insert behaves in a braze. And the shape and dimensional tolerance of the insert change the contact pattern on the edge, which changes the load the material sees.
The practical consequence is that a cross-reference is a shortlisting tool. It narrows a field of candidates to two or three that are plausibly equivalent, and everything after that is a comparison of measured values and a test on a real route.
Coating and substrate differences
Coating is the property most likely to be carried over from a cutting-tool chart without thinking, and on a bonded plow insert it usually works against the application. A coating is a thin layer applied to improve the behaviour of a cutting edge; on an insert that has to be brazed to steel, that layer sits at exactly the interface where the filler metal needs to wet the surface.
Two consequences follow. A coated insert may need the coating removed before bonding, which is an extra process step and a potential source of inconsistent joints. And where the coating is left in place, an incompletely wetted joint can result, which produces exactly the kind of insert loss that is later diagnosed as a material problem. The failure signatures involved are set out on the insert loss page.
The substrate is what a wear part is being chosen for. Where a supplier’s chart leads with a coating as the reason two grades differ, the useful question is what the underlying substrate would do without it.
Questions to ask when substituting
Substitution can be handled as a short interrogation, and the answers are what turn a chart position into a decision.
- What is the grain size class, and by what method was it measured?
- What is the binder content, and has it changed from the grade being replaced?
- What hardness and strength values are reported, and against which test standards?
- Is the insert coated, and if so can it be supplied uncoated for a bonded application?
- What dimensional tolerance applies to the dimensions that locate the insert?
The second question is the one that most often explains a performance change that the hardness figure does not. Two grades at the same hardness with different binder content behave differently in a cold, abrasive duty, and the difference is invisible on a chart that reports hardness alone. How the two ends of that trade-off behave is set out on the micro-grain and standard grain page.
Testing a substitution safely
A substitution is a comparison, and it only produces usable evidence if it is run as one.
- Fit the substitute to part of the fleet and keep the original grade on the rest of it.
- Hold everything else constant: same route mix, same drivers, same rotation practice, same inspection method.
- Record insert height at removal and the positions that wore first, on both groups.
- Record the number of service events each group needed, not only the wear at the end.
The third and fourth items together are what make the test decisive. A substitute that wears at the same rate but needs more service events is not equivalent, and a comparison based only on final measurements would miss that entirely. Where the substitute is being tested against a cold-weather duty, the seasonal conditions to specify are covered on the cold and abrasive conditions page.
Documenting a substitution
Once a substitution has been accepted, the record is what stops it drifting. Three items belong in it: the original grade and its four values, the substitute and the same four values, and the test result expressed in the fleet’s own unit for service life.
Two further notes save time later. Record whether the substitute is coated and whether the joint process changed as a result. And record the drawing revision the substitute inserts were produced to, since a grade change and a dimensional change are easy to make in the same order and hard to separate afterwards. Documentation practice of this kind follows the conventions published by ASME, and the receiving checks that confirm a lot matches what was ordered are set out on the delivery inspection page.
Reading a chart when two suppliers both look suitable
The final decision usually comes down to two candidates that both sit in the right place on the chart. The table below sets out what to compare at that point.
| Comparison | Why it decides the outcome |
|---|---|
| Binder content at equal hardness | Explains differences in impact behaviour that hardness alone does not |
| Grain size class and the sintering route behind it | A fine class that is not held through production does not deliver the fine structure |
| Coated or uncoated, and the bond process | A coating changes whether the joint can be made consistently |
| Dimensional tolerance on location features | Changes the seat fit, which changes the load path |
| Batch documentation offered | Determines whether a later claim can be argued at all |
The last row is the one that separates two suppliers who are otherwise indistinguishable on paper. A supplier who can tie a delivered lot to a production record is offering something a chart cannot show, and that is often the difference between a grade question being resolvable and being argued about for a season.
SENTHAI manufactures tungsten carbide inserts and plow edges in Rayong, Thailand, and reports grade values with the measurement method behind them so two specifications can be compared on the same basis. Material data published by carbide producers such as Plansee and Hyperion Materials & Technologies is useful for reading the property data behind a designation, and substitutions that need to be matched against an existing specification can be discussed through the contact page.
FAQ
Can I substitute one supplier’s grade for another using a cross-reference chart?
A cross-reference tells you which grade is nearest in a stated property, not which one will perform the same. Two grades can sit at the same hardness with different grain size, binder content and toughness, and behave differently on the same edge. Use the chart to shortlist, then compare measured values and test the substitute.
Why don’t two suppliers’ grade designations line up?
Because most designations are proprietary. A supplier’s own code describes a grade they produce, not a position on a published scale, and each supplier’s testing and production route differ. The values behind the code, not the code itself, are what can be compared between two suppliers.
Does a coating matter on a brazed plow insert?
Usually it is a disadvantage rather than a benefit. Coatings are developed for cutting tools, where the edge is disposable and the insert is clamped. On a plow insert the insert has to be bonded to steel, and a coating layer can interfere with the filler wetting the surface. What matters is the substrate, not a coating designed for another application.
How do you test a substitution before committing to it?
Run it as a comparison rather than a replacement. Fit the substitute to part of the fleet for a season, keep the original on the rest, and record the same measurements on both so the comparison has a baseline. Nothing else about the edge, the route or the inspection routine should change at the same time.
Send the grade you are running today and the property values you have for it. The SENTHAI engineering desk will report the same values for a candidate substitute so the two can be compared on one basis.
This article is one step in the Carbide Insert Selection and Replacement Guide, which covers grade, geometry, spacing, fitment tolerance and the replace-or-re-plate call.