Discussion

The results of the study have shown that ceramics can make an important contribution to solving the wear problems experienced in advanced heat engines. Wear coefficients approaching those obtained with current conventional piston rings were measured using ceramic-based coatings and a synthetic lubricant at 260 C. Since monolithic ceramics may be difficult to apply in ring applications, the coatings offer a practical approach for using ceramics. The need for materials having inherently higher wear resistance was demonstrated by the unacceptable wear coefficient measured with conventional chromium plated rings with cast iron cylinder specimens at 260 C. The wear coefficient of the cobalt-bonded tungsten carbide coating under the same

Table 3. Comparison of Approximate Ring Wear Coefficients

Ring Material

Cylinder Material

Lubricant

Temperature, C

Ring Loading, N/mm

Friction Coefficient

Hardness Used in Calculation, kg/mm2

Average Ring Wear Coefficient

Cr

Cast Iron

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