The Effect of Oscillating Traverse Welding on Performance of Cr-Fe-C Hardfacing Alloys HSUAN-HAN LAI, CHIH-CHUN HSIEH, JIA-SIANG WANG, CHI-MING LIN, and WEITE WU In this study, a series of experiments involving Cr-Fe-C hardfacing alloys is conducted to evaluate the effect of oscillating traverse welding on microstructure and performance of clad alloys. The alloys are designed to exhibit hypoeutectic, eutectic, and hypereutectic morphology. The morphology of the heat-affected zone (HAZ) of the unmelted metal, the solidified remelted metal, and the fusion boundary exhibited distinct characteristics. In the hypoeutectic and the eutectic alloys, the same lamellar eutectic structure can be observed as the solidified structure, and they also showed the same evolution in the HAZ. In the hypereutectic alloy, the incomplete weld pool blending results in a eutectic morphology instead of a fully hypereutectic morphology. The hardness result reveals that, for the hypereutectic alloy, the eutectic region, instead of the HAZ, is the weak point. The wear test shows that the hypoeutectic alloy exhibits the same wear behaviors in both the remelted metal and the HAZ, and so is the hypereutectic alloy; the eutectic alloy remelted metal and the HAZ have different wear morphologies. DOI: 10.1007/s11661-015-3093-z Ó The Minerals, Metals & Materials Society and ASM International 2015 I. INTRODUCTION THE hardfacing alloy is designed as a coating to protect the substrate under some severe environment. The coatings must be able to resist wear, abrasion, corrosion, or oxidation, depending on the coated alloys; therefore, the property of a coating is more important than the substrate. [1,2] The Cr-Fe-C series alloys, well known for their excellent resistance to abrasion, oxida- tion, and corrosion, have been extensively used in aggressive conditions, such as mineral processing, cement production, and pulp manufacturing. It has been reported that these alloys can exhibit hypoeutectic, eutectic, and hypereutectic morphologies, and that additional elements can affect their microstructural characteristics, mechanical properties, and abrasive wear behaviors. [3–10] The carbon content determines the solidified morphologies of the clad alloys and also the wear resistance. [4,5] The addition of silicon reduces the size of the primary dendrites and improves the corrosion resistance of the clad alloy. [6] The addition of the rare earth oxide can reduce the size of primary carbide and increase the wear resistance. [8] The addition of boron results in the formation of borides which coexist with carbides, enhancing the overall wear resis- tance. [9] Acting as composite materials, these alloys consist of a soft Cr-Fe solid solution matrix (the a or c phase) and carbide reinforcements (M 7 C 3 or M 23 C 6 carbide), and the formation of these phases is controlled by both the Cr and C contents. [2,11] For alloys consisting of M 7 C 3 , cracks will spread along the interface between the carbide and matrix because the M 7 C 3 hardness is extremely high, as compared with that of the Fe-Cr matrix. Commercial alloys, such as Fe-28Cr-C, with M 23 C 6 as the reinforcement, can be subjected to harsh abrasive conditions with good results. Presently, the alloy can be clad by arc welding or plasma welding. [7,10,12] To prepare a large clad area, multiple-pass welding is applied and it causes overlap- ping. [1,7] Under that condition, a part of the solidified weld is remelted and fused with the filler and solidifies as the newly solidified metal. In addition, in many studies on hardfacing alloys, the alloys are clad by an oscillating traverse welding process. [3–6,9,10,12] This process also leads to the remelting of a part of the clad metal. The unmelted part of the clad metal will be heated and becomes the heat-affected zone (HAZ). Most studies about hardfacing alloys focus on the performance of the clad weld, rather than on the HAZ. It has been reported that the wear behaviors of distinctive HAZ regions differ from each other and from the weld metal in the steel joints. [13] The morphology, microhardness, and residual stress will predominate over the performance of the HAZ. Recently, characteristics of the HAZ and its effect on the hypoeutectic alloy’s performance have been examined, [3] while the effects on the eutectic and hypereutectic alloy have not been reported yet. In this study, Cr-Fe-C alloys with hypoeutectic, eutectic, and hypereutectic structures were selected for investigation to determine the effects of oscillating traverse welding on the microstructural evolution and the performance of the three clad alloys. HSUAN-HAN LAI, CHIH-CHUN HSIEH, JIA-SIANG WANG, and CHI-MING LIN, Ph.D. Candidates, and WEITE WU, Professor, are with the Department of Materials Science and Engineering, National Chung Hsing University, 250 Kuo Kuang Road, Taichung 402, Taiwan, R.O.C. Contact email: wwu@dragon.nchu.edu.tw Manuscript Submitted April 14, 2015. METALLURGICAL AND MATERIALS TRANSACTIONS A