In Part 1, we left off at a tantalizing cliffhanger: pure tungsten carbide was as hard as diamond, but as brittle as a biscuit. The breakthrough took 30 years.

That breakthrough arrived in 1923.

At Osram in Germany, engineer Karl Schröter had a brilliant insight. He looked at concrete — hard aggregate bound together by cement — and applied the same logic to metals. He mixed ultra-hard tungsten carbide powder (the gravel) with cobalt powder (the cement), heated the mixture near cobalt’s melting point, then cooled it.

The result? A material that retained tungsten carbide’s extreme hardness, but gained enough toughness — thanks to cobalt — to survive real cutting forces.

In 1926, Krupp acquired the patent. The following year, at the 1927 Leipzig Machine Tool Exhibition, cemented carbide blades cut steel at speeds far beyond anything high-speed steel could handle — without softening, without failing.

Machining entered the cemented carbide era.

But HSS didn’t disappear. The two materials found their division of labor. Cemented carbide, hard and fast, took on cast iron and hardened steel. High-speed steel, tougher and more resilient, remained the go-to for drills, taps, and complex tools where chipping was the enemy.

Yet the first-generation cemented carbide had a fatal flaw.

Tungsten carbide is hard. Its melting point is sky-high. But its chemical stability is mediocre. When cutting steel at high temperatures, the carbon in WC gets “stolen” by the iron, forming crater wear — a crescent-shaped depression that destroys the cutting edge.

In the 1930s, metallurgists fixed this by adding titanium carbide (TiC). TiC locks the carbon in place, neutralizing crater wear. They also added tantalum carbide (TaC), boosting high-temperature strength and thermal shock resistance.

A classification system followed:

🔹 K-class — pure WC-Co. For cast iron and non-ferrous metals. 🔹 P-class — WC + TiC. For steel. 🔹 M-class — WC + TiC + TaC. The all-rounder.

Later, as materials like nickel-based superalloys and hard/brittle steels pushed the limits even further, S-class and H-class grades were developed.

Then came the 1970s, and evolution shifted from internal chemistry to external armor.

Sandvik of Sweden pioneered Chemical Vapor Deposition (CVD), coating carbide inserts with just a few microns of titanium carbide. The GC series was born. The substrate provided toughness; the coating provided heat resistance. Same insert, several times the tool life.

After that, alumina coatings, titanium nitride coatings, and multi-layer composite coatings arrived one after another, pushing cemented carbide to new heights — again and again.

The evolution of cemented carbide is a story of complete role reversal.

From a reinforcement particle trapped inside steel and limited by its matrix… to a standalone material redesigned as the protagonist itself. From simple WC-Co, to the addition of TiC and TaC, to multi-dimensional surface armor.

Every step was humanity rebalancing the eternal tension between hardness and edge integrity.

And that balance? It is still shifting today.