Influence of fusing temperature on microstructure, wear and corrosion resistance of induction melted bimetal of Co-based alloy and AISI 4140 steel

Two bimetals composed of a Co-based alloy and AISI 4140 steel were fabricated by induction fusing 1200 IC and 1250 1C, respectively. Their microstructures were examined and their wear and corrosion resistances were investigated using a ball-on-disc system and immersion tests. The results show that the phases of the Co-based alloy of the bimetal, fused at 1200 1C, are inherited from its original power and consist of a Co-rich phase, a Cr-rich phase and W3CoB3; however, the effect of iron dilution cat, the formation of cr-CrFe and COO.72FeO.28. When fusing at 1250 oC. W3CoB3 decomposes to form C03B; increases the W content in the Co-rich phase thereby reducing the corrosion rate ofthe Co-rich phase and resulting in improved corrosion resistance ofthe bimetal. However, a higher fusing temperature caused significant drop in hardness due to severe alloy dilution by iron diffusing from AISI 4140 steel and resi in declined wear resistance. The associated wear behavior also changes from abrasion wear to oxidation wear. (C) 2009 Elsevier B.V. All rights reserved.