Mechanical Engineering - Production Engineering - Discussion

Machining operations of titanium alloys are considered to be difficult, due to its relatively high tensile strength, low ductile yield, Low tool-chip contact area.

Titanium and its alloys have gained widespread applications in aerospace, biomedical industries due to their following favourable properties: They are lightweight, possess high strength, have excellent fatigue performance and offer high resistance to an aggressive environment.

It is unfortunate that the above favourable properties in practical applications, prove to be a curse during machining:

Titanium alloys due to their high strength, low thermal conductivity and chemical reactivity with tool materials (at elevated temperatures), pose a hazard to the tool and significantly reduce the tool life.

In addition, a relatively low Young's modulus of titanium alloys leads to spring-back and chatter leading to the poor surface quality of the finished product.

Finally, during turning and drilling, long continuous chips are produced; causing their entanglement with the cutting tool and making automated machining near impossible.

The solution are;

Application of high-pressure coolant during cutting and drilling operations. This is quite expensive owing to coolant costs.

"Ultrasonic assisted machining" in which the tool is imparted an ultrasonic vibration with very low amplitude. Instead of continuous contact of the tool with work, this method offers an intermittent contact reducing the heat-affected zones at the chip-tool interface, work-flank interface etc. Thus increasing the tool life.

Titanium alloys due to their high strength, low thermal conductivity and chemical reactivity with tool materials (at elevated temperatures), pose a hazard to the tool and significantly reduce the tool life.

Machining titanium is challenging due to the following factors:

Chemical reaction: Titanium tends to react with the cutting tool material at high temperatures, leading to tool wear and reduced tool life.
Low thermal conductivity: Titanium has low thermal conductivity, which causes heat to concentrate at the cutting edge, further accelerating tool wear.
Low tool-chip contact area: The contact area is relatively small, which increases cutting forces and heat generation.

However, the primary reason in this context is the chemical reaction between the tool and the workpiece.

Option B is the right one.

Both B and C can be the answer.

Ref : SK Mondal.

For better machinability of any material, low tool-chip contact area is better.

So, the correct answer is B.

The machinability of titanium alloys is difficult due to their low thermal conductivity and elastic modulus, high hardness at elevated temperature, and high chemical reactivity.

C is the correct answer.

Ref:R.S. Kurmi.

Titanium has high chemical reactivity.