**4. Conclusions**

In summary, the experimental optimization of forming overhanging structures of 316L stainless steel and chromium–nickel alloy steel was studied by selective laser melting. By using different scanning strategies, upper-surface-remelting processes, boundary-scanning powers, and boundary-counting strategies, the forming effects of the upper surface and the upper and underside overhang surface were analyzed, and the effects of the processing strategies on the surface roughness were also discussed. The conclusions are as follows:

1. The forming effect of chromium–nickel alloy is better than the 316L stainless steel below the limit forming angle in the overhanging structure.

2. Upper surface remelting can reduce the value of surface roughness, decrease the defect of surface spheroidization, and improve surface forming quality. Surface quality is better with the increase of the number of remelting, but increasing surface remelting power is not conducive to improving surface quality.

3. The optimization of boundary remelting is beneficial to the forming of suspension structure. Multiple boundary counting is beneficial to improve the forming quality of the suspension structure below the limit forming angle, and the lower scanning power is more beneficial to the forming of boundary.

4. By comparing different scanning strategies, it is found that the application of 316L stainless steel in the chessboard scanning strategy is beneficial to forming in a certain range below the ultimate forming angle, and the forming quality beyond a certain range is still not optimistic. The meander scanning strategy is suitable for forming suspension structures above the limit forming angle.

**Author Contributions:** Data curation, W.S. and P.W.; Formal analysis, W.S. and P.W.; Investigation, Y.L.; Methodology, P.W.; Resources, Y.L.; Supervision, Y.L.; Validation, G.H.; Visualization, G.H.; Writing—original draft, P.W.; Writing—review & editing, W.S., P.W., and Y.L.

**Funding:** This work was supported by gran<sup>t</sup> 51505006 from the National Natural Science Foundation of China.

**Conflicts of Interest:** The authors declare no conflict of interest.
