Microstructure, tribological performances, and wear mechanisms of laser-cladded TiC-reinforced NiMo coatings under grease-lubrication condition

Abstract

NiMo-5%TiC, NiMo-15%TiC, and NiMo-25%TiC coatings were prepared on GCr15 steel by laser cladding (LC). The microstructure and the phases of the obtained coatings were analyzed using ultra-depth-of-field microscopy (UDFM) and X-ray diffraction (XRD), respectively. A ball-on-disk wear test was used to analyze the friction-wear performance of the substrate and the NiMo-TiC coatings under grease-lubrication condition. The results show that the grain shape of NiMo-TiC coatings is dendritic. The wear resistance of NiMo-TiC coatings is improved by the addition of TiC, and the depths of the worn tracks on the substrate and on the NiMo-5%TiC, NiMo-15%TiC, and NiMo-25%TiC coatings are 4.183 μm, 2.164 μm, 1.882 μm, and 1.246 μm, respectively, and the corresponding wear rates are 72.25 μm3/s/N, 32.00 μm3/s/N, 18.10 μm3/s/N, and 7.99 μm3/s/N, respectively; this shows that the NiMo-25%TiC coating has the highest wear resistance among the three kinds of coatings. The wear mechanism of NiMo-TiC coatings is abrasive wear, and the addition of TiC plays a role in resisting wear during the friction process.

Comparing and analysing the characterisation of laser cladding of CrNiW and CrNiFeAlZr powders on H13 tool steel

“…20,44 At high temperatures, the C in the powder formed the carbides Ni 3 C and Fe 2 C, which possessed a high hardness. 45 Fe 23 C 6 and γ-Ni are the principal phase constituents of Ni25 coatings, whereas Ni25 + (ZrO 2 + C) composite coatings comprise not only γ-Ni and (Fe, Ni) 23 C 6 , but also ZrC, NiZr 2 , Ni 7 Zr 2 and Fe 3 C. 46 The presence of a considerable amount of Cr 7 C 3 and Cr 23 C 6 carbides could result in a rather robust wear resistant structure that is resistant to sliding. 47…”

“…20,44 At high temperatures, the C in the powder formed the carbides Ni 3 C and Fe 2 C, which possessed a high hardness. 45 46 The presence of a considerable amount of Cr 7 C 3 and Cr 23 C 6 carbides could result in a rather robust wear resistant structure that is resistant to sliding. 47…”