How to Address Milling Cutter Plastic Deformation and Excessive Flank Wear?

1. Introduction

2. Root Causes Analysis

2.1 Plastic Deformation of Milling Cutters

• Excessive Cutting Temperature: High-speed cutting, large cutting depth, and large feed rate will generate a lot of cutting heat. When the local temperature of the cutter edge exceeds the recrystallization temperature of the tool material, its hardness and strength will decrease sharply, making it prone to plastic deformation. For example, when machining high-temperature alloys with HSS cutters, if the cutting speed exceeds 30m/min, the cutter edge is often squeezed and deformed.
• Mismatched Tool Material: Using low-hardness, low-temperature-resistance tool materials to machine high-strength, high-hardness workpieces (such as hardened steel, titanium alloys) will lead to insufficient load-bearing capacity of the cutter edge. For instance, carbide cutters without titanium coating are far less resistant to deformation than coated ones when facing high-temperature cutting environments.
• Unreasonable Cutting Parameters: Excessively large cutting force caused by improper parameters (such as excessive radial cutting depth) exceeds the bearing limit of the cutter. Even if the temperature is not extremely high, the cutter edge will still undergo plastic flow under the action of static pressure.

2.2 Excessive Flank Wear of Milling Cutters

• Abrasive Wear: Hard inclusions (such as carbides) in the workpiece material will scratch the tool flank, resulting in continuous wear. This is particularly obvious when machining cast iron with high graphite content or composite materials with reinforcing fibers.
• Diffusion Wear: Under high-temperature conditions, chemical elements between the tool and the workpiece will diffuse mutually. For example, when machining steel with tungsten carbide cutters, the carbon element in the steel will diffuse to the cutter, reducing the hardness of the tool surface and accelerating wear.
• Oxidation Wear: At high temperatures (usually above 500°C), the tool surface will react with oxygen in the air to form a loose oxide layer. This layer is easily peeled off during the cutting process, exposing a new tool surface to continue oxidation, forming a vicious cycle of wear.
• Poor Lubrication and Cooling: Insufficient cutting fluid supply, improper type selection, or uneven spraying will fail to effectively reduce the temperature of the tool-workpiece contact area and isolate the friction surface, thereby increasing the wear rate.

3. Targeted Countermeasures

3.1 Addressing Plastic Deformation

1. Optimize Tool Material Selection: For high-temperature and high-load machining scenarios, replace traditional HSS cutters with high-performance materials. For example, cubic boron nitride (CBN) cutters are suitable for machining hardened steel above HRC50, and polycrystalline diamond (PCD) cutters have excellent deformation resistance when machining non-ferrous metals such as aluminum alloys. For general alloy steel machining, choose fine-grained carbide cutters with high cobalt content to improve toughness and high-temperature strength.
2. Adjust Cutting Parameters Scientifically: Reduce the cutting heat and cutting force by optimizing parameters. Specifically, appropriately reduce the cutting speed (for example, reduce the cutting speed of carbide cutters when machining alloy steel from 150m/min to 100-120m/min) and increase the feed rate moderately to shorten the contact time between the cutter and the workpiece; at the same time, control the cutting depth and width within the range that the cutter can bear, avoiding excessive load on the single tooth of the cutter.
3. Adopt Advanced Coating Technology: Coating the cutter surface can significantly improve its high-temperature resistance and wear resistance. Common coating materials include titanium aluminum nitride (TiAlN), titanium carbonitride (TiCN), and aluminum chromium nitride (AlCrN). Among them, TiAlN coating has good oxidation resistance at high temperatures (up to 800°C), which can effectively isolate the cutter from the high-temperature environment and prevent plastic deformation.

3.2 Solving Excessive Flank Wear

1. Enhance Abrasion Resistance of Tools: Select tool materials with high hardness for machining workpieces containing hard inclusions. For example, use ceramic cutters instead of carbide cutters when machining cast iron, or choose carbide cutters with TiCN coating (higher hardness than TiAlN coating) to improve the scratch resistance of the flank.
2. Control Cutting Temperature to Inhibit Diffusion and Oxidation: On the one hand, optimize the cutting parameters to reduce heat generation; on the other hand, improve the cooling and lubrication effect. Use cutting fluids with good thermal conductivity and lubricity (such as emulsion for general machining, and synthetic cutting fluid for high-speed machining) and adopt the internal cooling method of the cutter if conditions permit, so that the cutting fluid can directly reach the tool-workpiece contact area. For dry machining that is environmentally friendly, choose tools with high-temperature-resistant coatings and strictly control the cutting speed.
3. Optimize Tool Geometry: Reasonably design the flank clearance angle and edge radius. Increasing the flank clearance angle can reduce the contact area between the flank and the workpiece, thereby reducing friction and wear; the edge radius should be matched with the cutting parameters—too small will lead to insufficient edge strength, and too large will increase the contact area and cause severe wear.
4. Strengthen Tool Management and Maintenance: Establish a regular tool inspection mechanism, use a tool microscope to measure the flank wear amount, and replace the tool in time when the wear reaches the critical value (usually 0.3-0.5mm for finishing cutters). After use, clean the tool with a special cleaning agent to remove cutting chips and cutting fluid residues, and store it in a dry and shock-proof tool cabinet to avoid secondary damage.

4. Conclusion