A Novel Austenite Aging Steel Laser Cladding Coating and Its Elevated-Temperature Wear Resistance
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INTRODUCTION
AISI H13 steel is widely used to make hot-working dies due to its high hot strength, toughness and thermal fatigue resistance.[1–4] One of its main failure modes is an elevated-temperature wear because of long-playing heating and sliding, which causes the variation of dimension and shape of the dies. Therefore, the dies fail prematurely, especially in severe working conditions.[2–6] However, the elevated-temperature wear performance (at 600C or above) of H13 steel cannot be improved by heat treatment or microstructure variations. Hence, surface treatment would be an effective route to improve elevated-temperature wear performance of H13 steel.[6–8] Laser cladding (LC) has obvious advantages over other surface treatment technologies: fine grains with rapid solidification characteristics, low dilution rate, small heat input and good metallurgical bond.[6,9,10] For laser cladding, laser energy is absorbed to melt cladding materials to form a coating on the surface of the
W. JIANG, L. WANG, and S.Q. WANG are with the School of Materials Science and Engineering, Jiangsu University, Zhenjiang 212013, China. Contact email: [email protected] Manuscript submitted September 13, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS B
substrate to improve its surface performance.[9] Clearly, the alloy composition of cladding materials is a key factor deciding the performance of the coating. Currently, for cladding materials, Fe-, Co- and Ni-based alloys were extensively studied and commercially applied to fabricate laser cladding coatings.[10–15] Compared with Co-based and Ni-based alloys,[11,12] Fe-based alloys were reported to have many merits of low cost, increased wear resistance and hardness.[10,13–15] Therefore, Fe-based alloys are suitable for the surface strengthening of ferrous alloys because of their full mutual solubility. For most of Fe-based alloys, carbides are usually used as main strengthening phases to improve strength and wear resistance.[6,13–15] However, carbides readily coarsen at high temperatures to lose their reinforcing effect. Therefore, at high temperatures, Fe-based alloys would be thermally softened not to provide high deformation resistance and wear resistance. Rahmana et al. reported that the laser cladding HSS alloys possessed higher wear resistance at room temperature but experienced severe wear at 500 C.[16] It may be considered that the inferior wear resistance of H13 steel is attributed to the above-mentioned thermal softening caused by the coarsening of carbides. Consequently, thermal softening (plastic deformation) and elevated-temperature wear might be a big obstacle for the application of hot-working dies made by H13 steel or Fe-based alloy coatings. In order to avoid the failures resulted from thermal
softening and elevated-temperature wear, the coarsening of strengthening phases at high temperatures should be retarded. Intermetallic compounds would be better substitutes for carbides as strengthening phases, just like maraging steel. Yin et al. found that the wear resist
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