Cermet vs. Carbide Inserts: Why High‑Precision Bevelling Wins the Weld Prep Game

In structural steel fabrication, plate bevelling is fundamental to joint integrity and weld quality. Unlike roughing operations, it leaves no room for built‑up edge, as any edge contamination can compromise bevel geometry, disrupt weld fit‑up, and lead to unsuccessful visual or NDT inspections.

Although many bevelling machines appear similar at first glance, their real performance is defined at the cutting edge – specifically by the insert material. PROMOTECH bevelling machines rely on two proven technologies: cemented carbide and cermet cutting inserts. Both are proven, both are widely used, and both have clear strengths and limitations.

While cemented carbide has long been the “workhorse” of the industry, stricter WPS (Welding Procedure Specifications) and EN ISO 9692 standards are pushing cermet to the forefront of modern workshops. Here is why cermet cutting inserts for bevelling are gaining a decisive edge over traditional carbide inserts in in modern fabrication shops.

What Are Cermet and Carbide Cutting Inserts?

Cermet is a composite material composed of ceramic (titanium carbide, TiC)  and metal (titanium nitride (TiN). Adding metal powder to ceramic allows it to withstand high temperatures without becoming easily breakable. This way cermet combines the high hardness of ceramics with the toughness of metals, offering excellent wear resistance and thermal stability. It is a precision cutter engineered for finish quality.

Cermet cutting inserts for bevelling provide:

• Ceramic hardness and wear resistance
• Metallic toughness and thermal stability
• Extremely low chemical affinity for steel

What is carbide?

Cemented carbide is a powdery metallurgical material: a composite of tungsten carbide (WC) particles and a binder rich in metallic cobalt (Co). Hard carbide grains do the cutting, while the cobalt keeps things from cracking under pressure.  It combines hardness with toughness, making it suitable for a wide range of machining applications. Carbide is well suited for rough or unprepared plates, as well as handheld bevelling operations where vibration levels are higher.

Carbide cutting inserts for bevelling provide:

• Toughness and impact resistance
• Good thermal conductivity
• Durability under harsh cutting conditions

Metallurgical Contamination (No BUE)

A major headache when using carbide on on mild and low-carbon steels is the formation of a Built-Up Edge (BUE), where material “welds” itself to the insert and then smears onto the bevel. This degrades the bevel surface and introduces inconsistencies that can affect weld fit up and inspection results.

With its very low chemical affinity for steel, cermet eliminates BUE, keeping the cutting edge clean and stable over long passes and delivering a smoother, more uniform bevel. This leaves the bevel metallurgically clean, preventing tool material micro-inclusions from contaminating the weld pool and compromising weldability.

Wear resistance

Tool life in finishing operations is another area where cermet cutting inserts excel. Cermet’s low thermal expansion and fine grain structure help maintain sharp cutting edges, delivering dimensional accuracy over much longer distances than carbide. Because wear develops more slowly and predictably, the cermet inserts maintain consistent performance over a longer portion of their life.

Superior Surface Finish for NDT-Ready Joints

Carbide inserts remain strong in roughing and heavy material removal, but when the operation shifts from removal to refinement, cermet’s wear resistance and edge stability provide a clear advantage.

Thanks to its high hardness, refined microstructure, and ability to maintain a sharp cutting edge, cermet produces bevels with noticeably lower roughness and better dimensional consistency. This minimizes the risk of slag entrapment or porosity.

For welded structures that must pass radiographic testing, this bevel consistency and surface integrity are no longer optional but critical. Surface finish is where cermet clearly moves ahead of carbide.

Boosting Productivity in High-Volume Manufacturing

Another decisive factor is thermal behaviour. High hot hardness enables cermet inserts to maintain their hardness and edge stability at elevated temperatures better than cemented carbide, allowing bevelling machines to operate at significantly higher cutting speeds without accelerated tool wear — ideal for automated bevelling machines. In practice, cermet allows cutting speeds from 20% to 50% higher. As a result, faster V‑, X‑, or J‑groove preparation means welding stations spend less time waiting for material, producing more finished workpieces in less time, improving overall line efficiency.

In high‑volume production environments, cermet higher speeds combined with longer tool life mean:

• Shorter processing time per running meter (cycle time)
• Reduced rework and post‑processing
• Fewer tool changes
• More efficient use of production capacity

Furthermore, cermet’s hot hardness prevents excessive edge overheating, minimizing the Heat Affected Zone (HAZ) before the arc even strikes.

“Ready-to-Weld” Edge Quality

Unlike grinding, bevelling with a use of cermet inserts does not introduce abrasive dust or disc contaminants into the material structure. The surface is ready for welding immediately after degreasing. cermet guarantees a clean edge without “tears” or gouges, eliminating potential initiation points for hot cracking.

Application Requirements

Of course, no cutting tool is perfect and cermet is not without limitations. Understanding them is essential to using it successfully. Compared to carbide, cermet is more brittle and does not like interrupted cuts or uneven plate edges. In bevelling applications this means that machine rigidity, proper clamping, and well prepared plate edges are critical. Uneven edges, excessive vibration, or aggressive entry conditions can lead to edge chipping. For this reason, cermet performs best in controlled, continuous cuts on stable machines.

Cermet inserts are the top choice for:

• High‑speed bevelling with stable machines
• Applications where bevel appearance matters (visible joints, fit‑up accuracy)
• Precision bevels for RT‑inspected welds
• Finishing operations on steel and stainless steel

PROMOTECH cermet inserts

PROMOTECH controlled comparative tests confirm that cermet cutting inserts consistently outperform carbide when machining carbon steel, particularly in finishing operations.

In the case of the PROMOTECH BM‑21 bevelling machine, the observed performance improvement exceeds 50% compared to carbide inserts. Cermet cutting inserts used in PROMOTECH bevellers provided better surface quality, more stable cutting behaviour and reduced built‑up edge. For other bevelling machines in PROMOTECH portfolio, the performance gain with cermet was up to 20 %. These results clearly indicate that, under stable conditions and with properly selected cutting parameters, cermet cutting inserts offers a measurable and repeatable advantage over carbide in carbon steel applications.

PROMOTECH offers 3 models of cermet inserts:

• PLY-000735 Cermet (LPEX) for BM-18 and BM-18A
• PLY-000756 Cermet (LPEX) for BM-25, BM-30 WM, and ABM-30
• PLY-000781 Cermet (SEMT) for BM-20plus, BM-21, ABM-50, ABM-50 DD Vario, SBM-500, and PRO-40 PBS 2

Cermet vs. Carbide cutting inserts at a glance

Quality beats aggression

The growing use of cermet in professional bevelling reflects a broader shift in fabrication toward cleaner processes, higher standards, and greater efficiency. Carbide has been the industry’s workhorse for decades — reliable, versatile, and forgiving. As machines become more rigid and production methods more controlled, the limitations of cermet are easier to manage, quality beats aggression and cermet’s performance benefits become more evident.

Check the full range of PROMOTECH portable and stationary, pipe and plate bevelling machines >>