Why are cutting tools made of titanium or titanium alloys rare?

1. Weak performance compared to steel cutting tools
Measuring performance requires comprehensive consideration of service conditions. New enthusiasts who are new to the cutting ring often focus on hardness/strength, while ignoring other performance indicators. The major issue with titanium alloy as a tool material comes from its elastic modulus. The elastic modulus of titanium is 106.4 GPa at room temperature, which is 57% of that of steel. The elastic modulus represents the ability of a material to resist elastic deformation. This low value means that titanium alloy knives are prone to severe shaking during the production process, which affects the effectiveness of the cutting technique.
In fact, in 2012, the American company NEMO Arms launched an all titanium alloy AR10 assault rifle. In addition to the high cost problem caused by titanium alloy processing, the violent shaking of the gun god due to the low elastic modulus also affects its performance. Obviously, this product with limited performance and extremely high cost can only become a high-end toy like the Golden AK.
In addition, titanium alloy is weaker than structural steel in terms of hardness and wear resistance. Titanium alloy is not easy to grind, which gives people the illusion of wear resistance. In fact, titanium alloys have poor wear resistance and are prone to adhesive wear. After playing with it for a while, the scratches on the mirror caused trouble for tool enthusiasts with OCD.
The major obstacle of using titanium alloy as a tool material lies in the issue of matching strength and toughness.
In the production process of steel cutting tools, manual forging is a common process, which optimizes the microstructure inside the tool and improves its strength and toughness. More importantly, steel has a unique strengthening and toughening property - martensitic transformation. After heating to the fully austenitized temperature, the steel is rapidly cooled to room temperature, resulting in a non-equilibrium solid phase transition (carbon atoms are difficult to achieve effective migration, forming a non diffusive phase transition). After quenching, the steel has high strength and hardness but insufficient toughness. When combined with the tempering process, martensite is transformed into tempered martensite, forming a good match between strength and toughness. Additionally, the process of martensitic transformation can be controlled through other means. For example, Japanese knives are made with specially made clay on the back of the knife before quenching. During quenching, the cooling rate of the area covered by clay is slower than the critical value, resulting in the formation of martensite on the back of the blade. This forms a good and tough combination of the blade/back. In fact, Japanese knives are straight before quenching. After quenching, the volume expansion of martensitic transformation at the blade area caused the blade to bend. Of course, the cutting tool itself forms a bimetallic structure during the forging process, which is also difficult to achieve in the production of titanium alloy cutting tools, so it will not be elaborated here.
On the other hand, titanium alloys, although α Type and α+β Type titanium alloys exhibit allotropy transformation and have the basis for martensitic transformation. However, due to the absence of a migration mechanism similar to carbon in steel, toughness decreases and strength does not show any improvement. So this restricts the performance of titanium alloy cutting tools.
2. Difficulty in processing and high manufacturing costs
The reserves of titanium on Earth are not significant, and the high cost is due to its processing difficulties. Titanium itself has high activity, and its corrosion resistance at room temperature is due to the formation of an oxide film. It is easy to absorb oxygen and nitrogen during high-temperature processing. Generally, it involves vacuum equipment. In addition, titanium alloy grinding is difficult. This is clearly not compatible with traditional tool processing processes (forging, heat treatment, grinding). If titanium alloy is used as a tool, it will increase the manufacturing cost and make rockets fly into the sky, and the performance may not be very good. If you have money and are capricious, you should choose the more expensive one rather than the better one. Why not use gold or silver to create it? The cost is mainly reflected in the raw materials, and the processing loss is not high. Besides being competitive, it can also resist inflation. Let's learn more about it?
3. Potential corrosion issues
Titanium alloy itself is very corrosion-resistant. But the problem also lies in this. Because it is difficult to make a knife from head to toe with a single material. Once titanium comes into contact with other metals such as aluminum and steel, there is a risk of galvanic corrosion. A high cost titanium alloy sword, after years of collection by enthusiasts, was found to have lost its handle, handguard, and scabbard.
The above are the general reasons why titanium alloy cutting tools have not become mainstream. Of course, titanium alloy cutting tools have characteristics such as lightweight, paramagnetic or diamagnetic properties, and the ability to form beautiful oxide films, which still have practical significance.