Stainless steel is an important metal material. 316L stainless steel is widely used in various industrial fields due to its good processing performance and excellent corrosion resistance. However, the strength of 316L stainless steel is not comparable to the lighter density of aluminum and titanium alloys, and it is difficult to meet future industrial needs. The ASTM standard stipulates that the properties of 316L are yield strength> 170 MPa, tensile strength> 485 MPa, and elongation> 40%. Therefore, strengthening 316L is imminent.
The academic journal "Composites Part B: Engineering" published a paper titled "Selective laser melting of dispersed TiC particles strengthened 316L stainless steel". This paper reveals a method for strengthening 316L stainless steel. In this method, the research team uses selective laser melting (SLM) metal 3D printing technology and a 316L stainless steel 3D printing material with TiC micron particles to increase its yield strength To 832MPa.
TiC micron particle reinforced material
The main reason for the increase in strength
According to the description of the paper, the selective laser melting 3D printing technology is a new method to strengthen 316L stainless steel. The extremely fast cooling rate of selected laser melting (up to 10^6K/s) results in high dislocation density in 316L stainless steel. This is the main reason why selective laser melting technology can strengthen 316L. Generally speaking, the yield strength of 316L material manufactured by laser melting in the selected area can reach about 600 MPa, and the elongation can reach more than 50%.
In this study, the author added 1wt.% and 3wt.% TiC micron particles to make the printed 316L-1TiC and 316L-3TiC yield strengths of 660 MPa and 832 MPa. Analysis shows that this strengthening comes from grain refinement and second phase strengthening. Through comparison with related literature, their research results (strength and plasticity) are better than 316L stainless steel reinforced by nano-TiC particles.
The main reason is the higher density of the samples they used and good 316L/TiC interface bonding. The paper pointed out that when choosing the ceramic reinforcing phase of the metal, the wettability of the reinforcing phase and the matrix is very important. The wetting angle between TiC and stainless steel is only 30°. Therefore, 316L stainless steel can easily grow on TiC particles during the solidification process.
The yield strength of 316L produced by selective laser melting additive manufacturing is much higher than that of traditional 316L stainless steel because of its high dislocation density. After adding 1% of micron-level TiC particles, the yield strength of the material was increased by 10%, but the elongation did not decrease. After adding 3% TiC, the yield strength of the material increased by 40% to 832 MPa, but the plasticity decreased to 29%.
This paper discusses the use of selective laser melting 3D printing methods to strengthen 316L stainless steel by introducing micron-level TiC particles. The results show that the strength of 316L stainless steel can be greatly improved. At the same time, plasticity is maintained at a high level. This method is expected to overcome the low-strength short plate of austenitic stainless steel and further expand its application in the industrial field.