Taboos in Using Diamond Tools for Machining Aluminum Alloys

Prohibitions on the Application of Diamond Tools in Machining Aluminum Alloy Parts

Diamond tools, primarily made of polycrystalline diamond (PCD), offer exceptional hardness, wear resistance, low friction coefficient, high elastic modulus, high thermal conductivity, low thermal expansion coefficient, and minimal affinity for non-ferrous metals. These properties make them an ideal choice for precision machining of non-ferrous materials such as aluminum alloys. Additionally, diamond tools allow for higher cutting speeds compared to carbide tools, significantly improving machining efficiency and surface quality.

However, diamond tools exhibit notable limitations when machining ferrous metals (e.g., steel materials). Since steel contains a high proportion of carbon, and diamond itself is an allotrope of carbon, the carbon atoms on the tool surface tend to adhere to chips and the workpiece during machining, leading to cutting-edge blunting. This results in increased temperatures in the machining zone. Under high temperatures and oxygen-rich conditions, diamond may undergo carbonization, manifesting macroscopically as graphitization, thereby accelerating tool failure.

In modern automotive manufacturing, to meet lightweight and functional integration requirements, die-cast aluminum alloy parts often incorporate insert processes, embedding different materials (e.g., cast iron, stainless steel) into the aluminum alloy matrix. Machining such composite materials imposes higher demands on tool selection. Given the high cost of diamond tools, their rational application requires a thorough understanding of their characteristics to leverage advantages and mitigate disadvantages.

Below are specific prohibitions and precautions for diamond tools in machining aluminum alloy parts:

### 1. Prohibition on Machining Aluminum Alloy Parts with Iron Inserts

**Typical Part: Aluminum Alloy Engine Block**

Engine blocks are typically made of die-cast aluminum alloy, but to enhance wear resistance, cast iron inserts are often embedded in the cylinder liner sections. When machining the upper surface of such parts, using diamond tools on the cast iron areas will cause rapid wear due to carbon affinity. In such cases, carbide tools should be used instead to avoid unnecessary cost losses.

### 2. Caution When Using Diamond Tools for Parts with Local Stainless Steel Inserts

**Typical Part: Aluminum Alloy Gear Housing for Diesel Engines**

Gear housings, which feature complex lubricating oil channels, often incorporate pre-formed stainless steel tubes via insert die-casting. Machining such parts requires zonal processing:

1. **Pure Aluminum Alloy Areas (e.g., Large End Faces)**: Suitable for diamond tools, ensuring efficient cutting and excellent surface quality.

2. **Stainless Steel Insert Areas**: Switch to carbide tools and ensure the stainless steel sections are below the final machining surface height to prevent diamond tools from contacting the hard inserts.

### 3. Recommended for Machining Pure Aluminum Alloy Parts Without Inserts

**Typical Part: Aluminum Alloy Oil Pan**

For parts entirely made of pure aluminum alloy (e.g., large end faces and side surfaces of oil pans), diamond tools can fully demonstrate their advantages, particularly in face milling, significantly improving surface finish and extending tool life.

### Summary

The application of diamond tools must strictly adhere to material compatibility principles:

- **Suitable Scenarios**: High-efficiency precision machining of non-ferrous metals like pure aluminum or copper alloys.

- **Prohibited Scenarios**: Materials or inserts containing carbon-affinity elements such as iron, nickel, or cobalt.

- **Composite Parts**: Require zonal machining combined with carbide tools to mitigate risks.

By rationally planning process paths and tool selection, the performance advantages of diamond tools can be maximized while reducing machining costs.