Study on the Effect of Ni Addition on the Microstructure and Properties of NiTi Alloy Coating on AISI 316 L Prepared by Laser Cladding

Abstract

This paper investigated 55 NiTi commercial alloy powder and 55 NiTi with 5% pure Ni mixed powder (55 NiTi + 5 Ni) coatings fabricated by laser cladding to study the effect of extra Ni addition on the microstructure and properties of the coating. The XRD and EDS results show that the major phases in the coatings were NiTi and Ni3Ti. Besides that, a second phase like Ni4Ti3, Fe2Ti, and NiTi2 was also detected, among which, NiTi2 was only found in 55 NiTi coating. The proportion of the phase composition in the coating was calculated via the software Image-Pro Plus. The hardness of the cladding layer reaches 770–830 HV, which was almost four times harder than the substrate, and the hardness of 55 NiTi + 5 Ni coating was around 8% higher than that of 55 NiTi coating. The wear resistance of the 55 NiTi + 5 Ni coating was also better; the wear mass loss decreased by about 13% and with a smaller friction coefficient compared with the 55 NiTi coating. These results are attributed to the solid solution strengthening effect caused by Ni addition and the second phase strengthening effect caused by the content increase of the Ni3Ti phase in the cladding layer.

Searching New Solutions for NiTi Sensors through Indirect Additive Manufacturing

“…Hardness values are higher than the hardness of bulk NiTi (NiTi (B2) 275 HV, N (B19) 112 HV, NiTi2 163 HV and Ni3Ti 1071 HV [34][35][36][37]), confirming the presence of h phases (i.e., Ni3Ti) (Table 10). The hardness values are similar to those of NiTi 3D obje obtained from other non-conventional technologies (800 HV [38], 700 HV [39,40], and HV [41]). In composition C where Ni3Ti was not detected, a lower hardness was expect Indirect additive manufacturing, such as MEX, could be the sustainable technology ideal for applications where the geometry envisaged could be complex, but the thickness is less than 3 to 5 mm.…”

“…Hardness values are higher than the hardness of bulk NiTi (NiTi (B2) 275 HV, NiTi (B19) 112 HV, NiTi 2 163 HV and Ni 3 Ti 1071 HV [34][35][36][37]), confirming the presence of hard phases (i.e., Ni 3 Ti) (Table 10). The hardness values are similar to those of NiTi 3D objects obtained from other non-conventional technologies (800 HV [38], 700 HV [39,40], and 742 HV [41]). In composition C where Ni 3 Ti was not detected, a lower hardness was expected.…”

Corrosion Behavior of Nickel–Titanium Continuous-Casted Alloys

“…The grain size of each metal material depends on the nucleation centers and the crystal's growth during the solidification of the melt. The higher nickel content in the NiTi cc alloy affected the increase in the number of initial grains during the nucleation process [23,27,28]. The grain size reduction can improve the alloy's superelastic properties, as it allows the desired orientation and stability of formatted grains due to the possibility of producing a larger number of martensite plates [29].…”

Effect of Ni Addition on the Corrosion Resistance of NiTi Alloy Coatings on AISI 316L Substrate Prepared by Laser Cladding

“…The offset distance of the laser track was 0.4 mm, hence, the overlap ratio for multi-track cladding was fixed at about 55%. The processing parameters used were optimized based on our preliminary research [24,25]. Substrates were placed on the working stage with heating function and then heated to 250 • C to release the internal stress before cladding.…”

“…Since both 55NiTi alloy powder and Ni powder are commercial (cheaper and easy to obtain), this solution provides great potential to reduce the cost for the preparation of high-performance 60NiTi coatings, which have previously been produced with customized 60NiTi alloy powder. In our previous research, the effect of Ni addition on the microstructure and mechanical properties, including microhardness and wear resistance, of the NiTi coating was revealed [24]; in this work, the key aim was to study the effect of Ni addition on the corrosion resistance of the NiTi coating. The relationship between the microstructure and corrosion resistance of the NiTi coating, the mechanism of the passive film formation and the process of pitting initiation are intensively discussed in this paper.…”