المستخلص: |
Copper substrate specimens were coated by Fe-Si using thermal evaporation to three different thicknesses, then subjected to laser treatment by CW C02-laser (720 watt 0.05 cm beam diameter and 200 cm/sec beam speed) under vacuum ( 10-3 mm Hg) in an attempt to perform local alloying in a surface network of four tracks (each two are parallel and perpendicular to the other two). The visual and microscopic inspection revealed that intensive re-evaporation of the coating material has taken place, because of the high power density applied and the use of deep vacuum. The hardening of the surface and other features of the laser fused tracks observed and studied. The morphological features of the surface affected layers and their microhardness have been studied on oblique sections through the laser fused tracks. Intensive mass transfer has been observed. The hardness of central part of tracks (region of maximum power density) was raised, while the hardness of surrounding portions was lowered. The bottom of the laser fused tracks showed a number of spherical large voids causing a drastic decrease in hardness. The middle parts of the tracks showed columnar structure and relatively high hardness. The wear characteristics of the investigated laser treated specimens (determined by the pin on disc principles) confirmed the results of morphological and microhardness studies.
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