In the present study, the destruction reason of peykan engine valves has been investigated using elemental and structural analysis by optical and election (SEM) microscopes. EDX results show that the alloy used for seat coating is similar to Estellite 6. The presence of denderitic arms surrounded in a fine eutectic has been shown by optical and SEM images. This is a proof for similarity between coating alloy and Estellite 6.
Composition of coating in a Co-Cr-W ternary diagram indicates that denderitic arms are Co(a) which has been surrounded by a Cr7C3/Co solid solution eutectic. Metallographic investigations showed that carbides in the most regions of coating have been spheriodized, and this indicates unsuitable production process. Erosion pattern of surface merely shows the effect of coating material yielding.