SURFACE ALLOYING OF PURE IRON BY MOLYBDENUM AND TIN BY A CONTINUOUS-WAVE CO2-LASER

It is now well established that considerable improvement in the mechan ical/chemical properties of near surface regions of materials can be a chieved by the process of laser surface alloying. The change in chemis try at the surface is attained through the process of melting and mixi ng of a predeposited coating and a thin layer of the substrate. Rapid solidification of this molten region at the surface then results in th e development of very interesting microstructural features. In the pre sent work, an attempt was made to surface alloy pure iron by molybdenu m and/or tin by using a continuous wave CO2 laser. Morphology of the r esulting microstructural features was examined by optical as well as s canning electron microscopy and the compositional details were determi ned using an electron probe microanalyser. Microhardness measurements were carried out as a function of depth from the laser-treated surface . This paper discusses the results of these investigations and delinea tes the roles of the various parameters on the chemistry and microstru cture of the surface alloys formed as a result of laser treatment.