Tungsten-inert gas surface alloying of a low carbon steel

In the present study, SAE 1020 steel surface was alloyed with preplaced graphite, chromium and high-carbon-ferro-chromium powders by using a tungsten-inert gas (TIG) heat source, separately. The effects of thickness of the preplaced powder layer on the microstructure, hardness and wear resistance of the alloyed surfaces were investigated. Following the surface alloying, conventional characterization techniques, such as optical microscopy, scanning electron microscopy (SEM), energy dispersive spectrograph (EDS) and X-ray diffraction were employed for studying the microstructure of the alloyed surface. Hardness measurements were performed across the alloyed zone and wear properties of the surfaces were evaluated by a pin-on-disc abrasive wear testing method. The results indicated that different amounts of chromium, carbon and chromium with carbon could be obtained on the surface of the SAE 1020 steel, changing the thickness of the preplaced powder layer. The alloyed surfaces showed an increase in hardness and wear resistance and this was attributed to harder phases. However, the highest hardness and wear resistance surface was obtained for the high-carbon-ferro-chromium powder layer with a 2.4-mm layer. This was attributed to a higher volume friction of carbides (Cr7C3) in the microstructure. As a result, TIG arc heat source can be used effectively for surface alloying with a preplaced powder to improve resistance of the surface of the SAE 1020 steel to wear.