POWDER FOR ADDITIVE MANUFACTURING, USE THEREOF, AND AN ADDITIVE MANUFACTURING METHOD

Abstract

A powder for additive manufacturing, including, in wt. %, C<0.03; Ni 13.0-14.5; Co 12.0-14.0; Mo 7.0-8.0; Ti 0.05-1.00; and, as optionals Al 0-0.1; Cr 0.0-1.0; N 0-200 ppm; Si 0-0.10; Mn 0-0.10, and a balance of Fe and unavoidable impurities.

Claims

1. A powder for additive manufacturing, comprising, in wt. %: C<0.03 Ni 13.0-14.5 Co 12.0-14.0 Mo 7.0-8.0 Ti 0.05-1.0, wherein Ni+Mo+Ti?23 wt. %, and, as optionals Al 0-0.1 Cr 0.0-1.0 N 0-200 ppm Si 0-0.10 Mn 0-0.10 with a balance of Fe and unavoidable impurities.

2. The powder according to claim 1, wherein wt. % Ti?0.27*(10.70-wt % Mo) when 13.0?Ni?13.5%.

3. The powder according to claim 1, wherein wt. % Ti?0.27*(9.45-wt % Mo) when 13.5<Ni?14.5%.

4. The powder according to claim 1, comprising 13.5-14.5 wt. % Ni.

5. The powder according to claim 1, comprising 13.0-14.0 wt. % Co.

6. A use of a powder according to claim 1, in an additive manufacturing process in which the powder is subjected to melting followed by cooling with a cooling rate of 10.sup.4-10.sup.6 K/s.

7. The use according to claim 6, wherein the additive manufacturing process is a process in which a laser beam is used for melting a layer of powder deposited on a substrate.

8. An additive manufacturing method in which: a) a layer of powder according to claim 1 is deposited onto a substrate; b) at least a part of the deposited layer of the powder is molten and subjected to cooling with a cooling rated of 10.sup.4-10.sup.6 K/s; c) a further layer of powder is deposited onto at least a part of the previous layer that was subjected to melting and cooling in the step b); d) at least a part of the layer deposited in step c) is molten and subjected to cooling with a cooling rated of 10.sup.4-10.sup.6 K/s; and e) steps c) and d) are repeated.

9. The method according to claim 8, wherein a laser beam is directed towards the deposited powder in steps b) and d), a melt pool temperature being equal to or above a temperature at which oxides of Ti and Al in the melt pool are at least partially dissolved in a melt of the melt pool and reprecipitate in a form of nano-sized oxides upon fast solidification.

Description

EXAMPLES

[0063] The result of simulations made by means of Thermocalc on compositions according to the present invention are compared with the experimental data, as well as calculated values, available for steel corresponding to grades 18Ni300 and 13Ni400. The comparisons support the correctness of the theory behind the present invention.

[0064] The Thermocalc simulations and equations to estimate the yield strength of the materials built from the powder, in as-built and age hardened condition, according to the present invention and from the 18Ni300 and 13Ni400 powders have been done in the same way.

[0065] A summary of experimental and calculated results is shown in table 3:

TABLE-US-00003 TABLE 3 Exp. As- Ex. Peak Ex. Ex. Calculated Calculated built yield aged yield As-built Peak aged As-built Peak aged strength strength Hardness Hardness yield strength yield strength (MPa) (MPa) (HRC) (HRC) (MPa) (MPa) 18Ni300 1080 1900-2020 35 53-55 1170 1920 13Ni400 1280 2310-2480 41-44 60-61 1290-1310 2390 Invention 1180-1260 2280-2326

[0066] As can be seen in Table 3, the values achieved from the Thermocalc simulations and yield strength modeling equations of the materials built from the 18Ni300 and 13Ni400 powders corresponds well to the actual values which clearly indicates that the calculated values for the material built from the powder according to the present invention are correct.

Method of Production of Samples

[0067] It is suggested that samples are produced by means an additive manufacturing method in which [0068] a) a layer of the powder is deposited onto a substrate, [0069] b) the deposited layer of the powder is molten and subjected to cooling with a cooling rate of 10.sup.4-10.sup.6 K/s, and [0070] c) a further layer of powder is deposited onto at least the part of the previous layer that was subjected to melting and cooling in the previous step, and [0071] d) at least a part of the layer deposited in step c) is molten and subjected to cooling with a cooling rated of 10.sup.4-10.sup.6 K/s, and [0072] e) repetition of steps c) and d) until a test specimen is produced.

[0073] The method includes that a laser beam is directed towards the deposited powder in steps b) and d).

[0074] Builds in 18Ni300, 13Ni400 as well as the proposed steel, can be performed in an EOS M290 L-PBF machine equipped with 400 W Yb-fiber laser. The build plate can heat up to 40? C. and the build can be conducted in nitrogen atmosphere (?1000 ppm oxygen). Laser beam size is approximately 80 ?m, hatching distance is set to 0.11 mm, and layer thickness 40 ?m. Stripes can be used as a scan pattern with stripe width of 5 mm. The scan pattern can be rotated 67 degrees between layers. A process optimization experiment performed before deciding on the optimized processing parameters to produce the samples. An example of the process parameters is presented in Table 4. For the process optimization the widely used volumetric laser energy density (E) can be used.

[00001]$E=\frac{P}{v?h?t}$

where P is laser power (W), v is the scanning speed (mm/s), h is the hatch spacing (mm), and t is layer thickness (mm). Process optimization can be performed by printing 18 cubes (15?15?15 mm3). 9 of the 18 cubes can be processed using different laser energy densities by changing the laser power as the only variable (i.e., P series) while the rest of the samples might be processed by changing the scanning velocity as the only variable (i.e., S series). Processing parameters are adjusted to yield an equal volumetric energy density for the samples sharing the same numberings (e.g., P3 and S3). A more detailed description can be found in Table 4.

TABLE-US-00004 TABLE 4 Laser Power and Scanning speeds used in this work, please note that the nominal processing parameter used to print 18Ni300 is P4, S4 which was used to print the first batch of 13Ni400 samples in this report Laser Laser Laser Laser power speed power speed sample (W) (mm/s) sample (W) (mm/s) P1 345 960 S1 285 793 P2 325 960 S2 285 842 P3 305 960 S3 285 897 P4 285 960 S4 285 960 P5 265 960 S5 285 1032 P6 245 960 S6 285 1117 P7 225 960 S7 285 1216 P8 205 960 S8 285 13345 P9 185 960 S9 285 1479