Surface hardening of 92.5W-5.25Ni-2.25Fe (wt.%) heavy alloy was investigated at 1200-1500 K using ethanol as carbon source. The hardened surfaces were characterized by XRD, optical microscope and microhardness tester. Microhardness of the alloy increased from HV0.3 318 to 1640 with temperature. This was attributed to both increased thickness of WC shells formed on W grains and increased reaction depth as a result of higher C diffusion. Reaction pathways leading to WC formation were explained using thermodynamic and experimental results. (C) 2015 Elsevier B.V. All rights reserved.