Research and progress of laser cladding on engineering alloys: A review

Laser metal deposition was used to repair grooves on 20 mm thickness 316L stainless steel plates using two different 316L stainless steel commercial powders – Fe-0.15C-11.8Cr-0.15Mn-0.2Ni-0.031P-0.56Si-0.05S (wt.%) powder and Fe-0.09C-17.05Cr-1.2Mn-11.28Ni-0.019P-0.46Si-0.09S (wt.%) powder. Good comprehensive performance of fine metallurgical bonding with were successfully achieved under optimized processing parameters. The microstructure and mechanical properties (micro-hardness, ultimate tensile strength, bending strength, low-temperature impact toughness) of the repaired specimens were investigated. Results indicated that chemical composition (different element contents) of the powders played an important role in determining the microstructure, phases and properties of the specimens. It was found that the microstructure of the specimens repaired with Fe-0.15C-11.8Cr-0.15Mn-0.2Ni-0.031P-0.56Si-0.05S (wt.%) powder was homogeneous and consisted of Cr-rich martensite while a number of cellular dendrite were presented in microstructure of specimens repaired with Fe-0.09C-17.05Cr-1.2Mn-11.28Ni-0.019P-0.46Si-0.09S (wt.%) powder and the repaired specimens consisted of ferrite and austenite. Due to solid solution strengthening, the average hardness of the specimens repaired with former powder was higher than that of the specimens with later powder. However, in the aspect of mechanical properties, LMD with Fe-0.09C-17.05Cr-1.2Mn-11.28Ni-0.019P-0.46Si-0.09S (wt.%) powder had better performance than the specimens repaired with another kind of powder. The relationship between the microstructure characteristics and mechanical performances of the repaired specimens was also discussed.

Laser metal deposition as repair technology for 316L stainless steel: Influence of feeding powder compositions on microstructure and mechanical properties

Numerical and experimental investigation on microstructure and residual stress of multi-pass hybrid laser-arc welded 316L steel

In situ fabrication of titanium carbide particulates-reinforced iron matrix composites

Carbide-facilitated nanocrystallization of martensitic laths and carbide deformation in AISI 420 stainless steel during laser shock peening

Microstructure and properties of austenitic stainless steel reinforced with in situ TiC particulate

The effects of ultrasonic impact peening (UIP) and laser shock peening (LSP) on 316L stainless steel were compared in terms of surface morphologies, microstructural evolutions and mechanical properties. The grain refinement mechanisms by mechanical and laser shock wave were subsequently analyzed. Experimental results showed that both UIP and LSP produced micro-grooves with the same depth (~48 μm) at the surface of 316L. The nano-grain size induced by double UIP treatment (10–90 nm) was much smaller than that by triple LSP treatment (>70 nm) because the impact numbers and total impact energy of UIP were much higher. The mechanical twinning was almost complete absence in the sample by UIP. On the contrary, the mechanical twinning was frequently observed in samples by LSP. The magnitude of peak pressure determined the transition from dislocation-dominated mechanism (~680 MPa for UIP) to twinning-dominated mechanism (~2200 MPa for LSP). The resultant dislocation cell size by UIP was much smaller than that by LSP due to the difference of dislocation density caused by different shock wave speed and impact numbers. Additionally, the compressive residual stress on the surface by UIP was higher than that by LSP in both measuring direction. Furthermore, both grain refinement and high dislocation density induced by UIP contributed to a significant increase in the hardness (~433 HV) and yield strength (~447 MPa). By contrast, the LSP induced mechanical twins which can act as dislocation blockers significantly improved the yield strength (~423 MPa).

Microstructural characterization and mechanical behavior of ultrasonic impact peened and laser shock peened AISI 316L stainless steel

Numerical and experimental investigation of thermal field and residual stress in laser-MIG hybrid welded NV E690 steel plates

A novel underwater directed energy deposition (UDED) technique was developed for the on-site repair of marine equipment in an underwater environment. A special drainage nozzle was integrated with a laser cladding head to form the underwater manufacturing tool which ensured the successful repair of the damage zone on an HSLA-100 steel plate. The influence mechanisms of inherently complex heat-treatment cycles and kinetics involved in the UDED process on the microstructural formation/evolution process were systematically investigated using both experimental and numerical approaches. The mechanical properties, including microhardness, nanohardness, tensile strength and Charpy impact toughness of the UDED repaired samples were investigated and the results were compared with those repaired by in-air directed energy deposition (DED). The experimental results show that the rapid cooling rate accelerated by the water quenching effect promoted the formation of columnar austenite and the subsequent fine martensite. Compared with the DED samples, the activation energy values for the nucleation and growth of the precipitates in UDED samples were much lower due to the existence of high-density crystal defects and large internal residual stresses. The numerical results indicate that compared with DED, the cooling rate significantly increased and the peak temperature decreased during UDED. The average microhardness of the samples prepared by UDED (315–334 HV) was higher than that prepared by DED (307 HV). The tensile properties and impact toughness of the as-repaired samples by UDED were equal or even better than those obtained by DED owing to the formation of fine martensite and high dislocation densities in the UDED samples. This work clarifies the difference in metallurgical processes in air and underwater environments, which can provide guidance for future structural manipulation of materials additively manufactured in underwater environments.

Y. Lu

Papers

Microstructure and properties of austenitic stainless steel reinforced with in situ TiC particulate

Microstructural characterization and mechanical behavior of ultrasonic impact peened and laser shock peened AISI 316L stainless steel

Numerical and experimental investigation of thermal field and residual stress in laser-MIG hybrid welded NV E690 steel plates

Investigation of the underwater laser directed energy deposition technique for the on-site repair of HSLA-100 steel with excellent performance

Investigation on microstructure and mechanical properties of NV E690 steel joint by laser-MIG hybrid welding