In the field of clutch facings production, Wollastonite has emerged as a significant material within clutch facings friction materials. When integrated into clutch facings mixture and clutch facings mixes, it endows the clutch facings with distinct properties, which have both advantages and disadvantages.

Wollastonite is usually added to the clutch facings mixture at a weight percentage between 10% – 30%. Its needle – like crystal structure plays a crucial role in enhancing the performance of clutch facings. It acts as a reinforcement agent, improving the mechanical properties of the clutch facings. Additionally, it can also influence the friction characteristics and thermal stability of the final product.

Clutch facings with 15% Wollastonite content can maintain their structural integrity up to 1200°C. In a high – temperature resistance test, while clutch facings without Wollastonite started to deform at around 800°C, those with Wollastonite showed no signs of deformation until the temperature reached 1100°C. This high – temperature resistance is vital during high – load and high – speed clutch operations when a large amount of heat is generated.

Wollastonite has a relatively low thermal expansion coefficient. For clutch facings with 20% Wollastonite, the thermal expansion coefficient is approximately \(5.5\times10^{-6}/^{\circ}C\), which is about 30% lower than that of clutch facings without it (\(8\times10^{-6}/^{\circ}C\)). This property helps prevent the clutch facings from cracking or warping due to thermal stress during rapid temperature changes.

In a tensile – strength test, clutch facings with 25% Wollastonite demonstrated a tensile strength of 20 – 22 MPa, which is about 40% higher than that of clutch facings without Wollastonite (usually 12 – 14 MPa). The flexural strength also increased significantly. This improvement in mechanical strength allows the clutch facings to endure the mechanical forces during clutch engagement and disengagement more effectively.

Wollastonite – containing clutch facings exhibit better wear resistance. In a wear – test over 150,000 clutch engagement – disengagement cycles, the wear depth of clutch facings with Wollastonite was only 0.15 – 0.2 mm, while that of clutch facings without it was 0.3 – 0.35 mm. This reduced wear rate extends the service life of the clutch facings.

Wollastonite contributes to a stable friction coefficient in clutch facings. In a friction – coefficient test under different loads (50 – 300 N) and speeds (500 – 3000 RPM), the friction coefficient of clutch facings with Wollastonite remained within the range of 0.3 – 0.33, with a deviation of less than ±5%. This stable friction coefficient ensures smooth clutch operation and reliable power transfer.

The extraction and processing of Wollastonite can be relatively expensive. Incorporating Wollastonite into clutch facings can increase the production cost by 25% – 35% compared to clutch facings without it. This high cost may limit its widespread use, especially in price – sensitive markets.

Due to its needle – like structure, Wollastonite can be difficult to disperse evenly in the clutch facings mixture. Uneven dispersion can lead to inconsistent performance of the clutch facings. In a production – scale experiment, when the dispersion of Wollastonite was not optimized, the friction coefficient deviation of the clutch facings increased by about 10% – 15%, and the mechanical strength also showed more significant variations.

Although Wollastonite provides high – temperature resistance, at extremely high temperatures close to its melting point, it becomes brittle. In a high – temperature mechanical – property test, when the temperature reached 1150°C, the tensile strength of clutch facings with Wollastonite decreased by about 30% – 40% compared to that at 800°C. This brittleness at high temperatures may pose challenges in some high – performance clutch applications.

In conclusion, Wollastonite offers several advantages in the production of clutch facings, such as high – temperature resistance, enhanced mechanical strength, and stable friction performance. However, its high cost, processing difficulties, and brittleness at high temperatures are factors that need to be carefully considered. Further research and development are required to overcome these challenges and fully utilize the potential of Wollastonite in clutch facings friction materials.