Effect of La2O3 on Microstructure and Properties of Laser Cladding SMA Coating on AISI 304 Stainless Steel

Abstract

Known as having a stress self-accommodation characteristic, the laser cladding shape memory alloy (SMA) coatings have been widely used in material failure repair. Nevertheless, their further development is greatly limited by their low microhardness (250 HV0.2) and corrosion resistance. Benefiting from the capability of refined grain and adjusted microstructure, rare earth oxides play a key role in improving the properties of materials. Herein, to improve the microhardness and anti-corrosion of laser cladding SMA coatings, different amounts of La2O3 were doped in SMA coating. The influence of the different La2O3 doping amounts on the phases, grain size and microhardness was studied. The anti-corrosion of the SMA/La2O3 composite coating was explored in 3.5 wt.% sodium chloride solution. Results showed that the grain of the SMA/La2O3 composite coating is significantly refined. When doping with 0.9 wt.%, the refinement rate reaches 19%. Furthermore, based on the Hall–Petch effect, the microhardness of the SMA/La2O3 composite coating is increased to 450 HV0.2. At the same time, the anti-corrosion of the composite coating is enhanced due to the smaller grain size and fewer defects.

Improvement of the High Temperature Wear Resistance of Laser Cladding Nickel-Based Coating: A Review

“…The γ-Ni grains within the coating grow gradually when the temperature increases to 480 • C. In accordance with Hall-Petch equation, it is well known that the hardness of the coating decreases as the grain size increases, which eventually leads to a decrease in the abrasion resistance of the coating [12,13]. At 600 • C, the hard ceramic phase Cr 7 C 3 , which has a high content in the NiCrBSi coating, starts to coarsen and the hardness of the coating decreases [14]. CrB precipitation can be observed in the γ-Ni substrate at 700 • C, and this reduces the solid solution strengthening effect of Cr in the substrate.…”

Enhancing Aluminum-Based Composite Manufacturing: Harnessing Si3N4 Reinforcement via Stir Casting Technique

“…The addition of 7.5% Si3N4 reinforcement to the aluminum alloy resulted in a substantial improvement in tensile strength by 24.76%. This significant enhancement underscores the effectiveness of Si3N4 as a reinforcing agent in aluminum matrix composites [47]. The improved tensile strength is attributed to the synergistic effects of Si3N4 particles, which act as barriers against dislocation movement and contribute to load transfer mechanisms within the composite material.…”

“…The improved tensile strength is attributed to the synergistic effects of Si3N4 particles, which act as barriers against dislocation movement and contribute to load transfer mechanisms within the composite material. The presence of Si3N4 reinforcement helps to inhibit the propagation of microcracks and voids, thereby increasing the material's resistance to deformation and fracture under tensile loading [47]. Additionally, the homogeneous dispersion of Si3N4 particles throughout the aluminum matrix ensures that the reinforcing effect is uniformly distributed across the composite, leading to consistent improvement in tensile strength throughout the material.…”

Effects of Rare Earths on Microstructure and Wear Resistance in Metal Additive Manufacturing: A Review

“…RECs remain stable during additive manufacturing heat cycling and accumulate at GB during solidification, performing a pinning theory on grain growth. This can effectively limit grain growth and improve material properties [66]. Gao et al [67] discovered that Ce was concentrated at the GB of Ni-based coatings, resulting in resistance to GB growth.…”