Fig. 1. Structural representation of SLM forming equipment
Fig. 2. SEM image of 18Ni300 die steel powder
Fig. 3. Direction of choosing measuring points of hardness
Fig. 4. Forming samples
Fig. 5. Normal probability plot of prediction model
Fig. 6. Residual plot of prediction model
Fig. 7. Main effect plots of relative density
Fig. 8. Metallurgy porosity in sample No.22
Fig. 9. Contrast of normal weld and sunk weld. (a) Normal weld; (b) sunk weld
Fig. 10. Powder bed diagram of powder thickness over the range of particle size
Fig. 11. Main effect plots of hardness
Fig. 12. SEM image of experiment sample No.18
Fig. 13. Main effect plots of wear resistance
Fig. 14. Surface wear morphology of sample No.28
Fig. 15. Response optimized plot of GRG
Fig. 16. Internal morphology of verified sample
| Element | C | S | P | Si | Mn | Al | Ti | Mo | Co | Ni | Fe |
|---|
| Mass fraction /% | 0.03 | 0.01 | 0.01 | 0.1 | 0.1 | 0.15 | 0.8 | 5.20 | 9.50 | 18 | Bal. |
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Table 1. Chemical composition of 18Ni300 die steel powder
| Parameter | Symbol | Level of parameter |
|---|
| Level 1 | Level 2 | Level 3 | Level 4 | Level 5 | |
|---|
| Laser power /W | A | 150 | 200 | 250 | 300 | 350 | | Scanning speed /(mm·s-1) | B | 650 | 700 | 750 | 800 | 850 | | Hatching distance /mm | C | 0.05 | 0.08 | 0.11 | 0.14 | 0.17 | | Powder coating thickness /mm | D | 0.02 | 0.03 | 0.04 | 0.05 | 0.06 |
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Table 2. Levels of experiment parameters
| No. | Forming parameter | Response value |
|---|
| A /W | B /(mm·s-1) | C /mm | D /mm | Relativedensity (RD) /% | Hardness(HD) /HRC | Wear resistance(WR) /μm3 |
|---|
| 1 | 300 | 800 | 0.08 | 0.03 | 99.8 | 27.6 | 430780 | | 2 | 350 | 750 | 0.11 | 0.04 | 99.9 | 35.5 | 1226820 | | 3 | 250 | 750 | 0.11 | 0.04 | 98.2 | 39.7 | 883720 | | 4 | 300 | 700 | 0.14 | 0.05 | 97.5 | 43.4 | 533680 | | 5 | 200 | 700 | 0.14 | 0.05 | 93.8 | 33.5 | 450080 | | 6 | 250 | 750 | 0.11 | 0.04 | 99.2 | 39.1 | 1081940 | | 7 | 200 | 700 | 0.08 | 0.05 | 96.6 | 40.1 | 513880 | | 8 | 300 | 700 | 0.08 | 0.05 | 99.4 | 42.9 | 1454260 | | 9 | 200 | 800 | 0.14 | 0.05 | 96.0 | 33.6 | 1825140 | | 10 | 150 | 750 | 0.11 | 0.04 | 93.2 | 38.3 | 845880 | | 11 | 300 | 800 | 0.08 | 0.05 | 99.6 | 36.5 | 648780 | | 12 | 200 | 700 | 0.08 | 0.03 | 98.5 | 40.9 | 1901920 | | 13 | 250 | 750 | 0.11 | 0.02 | 99.9 | 36.1 | 915040 | | 14 | 250 | 650 | 0.11 | 0.04 | 99.4 | 36.5 | 998560 | | 15 | 250 | 750 | 0.05 | 0.04 | 98.7 | 37.3 | 831540 | | 16 | 300 | 700 | 0.14 | 0.03 | 99.6 | 39.3 | 156060 | | 17 | 300 | 800 | 0.14 | 0.05 | 95.7 | 39.2 | 816140 | | 18 | 200 | 800 | 0.08 | 0.03 | 99.9 | 40.9 | 917560 | | 19 | 300 | 700 | 0.08 | 0.03 | 99.7 | 39.0 | 860520 | | 20 | 250 | 750 | 0.11 | 0.06 | 99.8 | 40.7 | 818740 | | 21 | 300 | 800 | 0.14 | 0.03 | 96.1 | 38.1 | 600280 | | 22 | 200 | 800 | 0.08 | 0.05 | 94.0 | 38.2 | 621960 | | 23 | 200 | 700 | 0.14 | 0.03 | 97.9 | 39.7 | 1461940 | | 24 | 200 | 800 | 0.14 | 0.03 | 92.2 | 37.1 | 1505180 | | 25 | 250 | 750 | 0.11 | 0.04 | 95.8 | 40.6 | 651760 | | 26 | 250 | 750 | 0.11 | 0.04 | 94.9 | 41.1 | 604780 | | 27 | 250 | 850 | 0.11 | 0.04 | 95.1 | 40.6 | 415180 | | 28 | 250 | 750 | 0.11 | 0.04 | 98.8 | 37.3 | 765940 | | 29 | 250 | 750 | 0.11 | 0.04 | 98.8 | 39.0 | 724240 | | 30 | 250 | 750 | 0.17 | 0.04 | 92.0 | 40.7 | 290960 |
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Table 3. Data of forming samples
| Parameter | Principalcomponent 1 | Principalcomponent 2 | Principalcomponent 3 | Eigenvalue | Contribution /% |
|---|
| Relative density | -0.681 | 0.072 | -0.728 | 1.1910 | 39.7 | | Hardness | 0.417 | 0.856 | -0.305 | 0.9758 | 32.5 | | Wear resistance | 0.601 | -0.512 | -0.613 | 0.8332 | 27.8 |
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Table 4. Principal component analysis results
| No. | Normalization | GRC | GRG |
|---|
| RD | | HD | WR | RD | HD | WR |
|---|
| 1 | 0.0126582 | 1 | 0.1573551 | 0.9753086 | 0.3333333 | 0.7606239 | 0.7070 | | 2 | 0 | 0.5 | 0.6133138 | 1 | 0.5 | 0.4491097 | 0.6844 | | 3 | 0.2151898 | 0.2341772 | 0.4167918 | 0.6991150 | 0.6810345 | 0.5453801 | 0.6505 | | 4 | 0.3037974 | 0 | 0.2162945 | 0.6220472 | 1 | 0.6980369 | 0.7660 | | 5 | 0.7721518 | 0.6265822 | 0.1684098 | 0.3930348 | 0.4438202 | 0.7480440 | 0.5082 | | 6 | 0.0886075 | 0.2721518 | 0.5303289 | 0.8494624 | 0.6475410 | 0.4852819 | 0.6826 | | 7 | 0.4177215 | 0.2088607 | 0.2049534 | 0.5448276 | 0.7053571 | 0.7092667 | 0.6427 | | 8 | 0.0632911 | 0.031645 | 0.7435877 | 0.8876405 | 0.9404762 | 0.4020625 | 0.7698 | | 9 | 0.4936708 | 0.6202531 | 0.9560217 | 0.5031847 | 0.4463277 | 0.3434015 | 0.4403 | | 10 | 0.8481012 | 0.3227848 | 0.3951176 | 0.3708920 | 0.6076923 | 0.5585858 | 0.5000 | | 11 | 0.0379746 | 0.4367088 | 0.2822219 | 0.9294118 | 0.5337838 | 0.6392048 | 0.7202 | | 12 | 0.1772151 | 0.1582278 | 1 | 0.7383178 | 0.7596154 | 0.3333333 | 0.6327 | | 13 | 0 | 0.4620253 | 0.4347313 | 1 | 0.5197368 | 0.5349131 | 0.7146 | | 14 | 0.0632911 | 0.4367089 | 0.4825702 | 0.8876404 | 0.5337838 | 0.5088695 | 0.6673 | | 15 | 0.1518987 | 0.3860759 | 0.3869039 | 0.7669903 | 0.5642857 | 0.5637590 | 0.6446 | | 16 | 0.0379746 | 0.2594937 | 0 | 0.9294118 | 0.6583333 | 1 | 0.8609 | | 17 | 0.53164557 | 0.2658228 | 0.3780830 | 0.4846626 | 0.6528926 | 0.5694222 | 0.5629 | | 18 | 0 | 0.1582278 | 0.4361747 | 1 | 0.7596154 | 0.5340883 | 0.7924 | | 19 | 0.0253164 | 0.2784810 | 0.4035031 | 0.9518072 | 0.6422764 | 0.5534015 | 0.7405 | | 20 | 0.0126582 | 0.1708861 | 0.3795722 | 0.9753086 | 0.7452830 | 0.5684581 | 0.7874 | | 21 | 0.4810126 | 0.3354430 | 0.2544419 | 0.5096774 | 0.5984848 | 0.6627415 | 0.5811 | | 22 | 0.746835443 | 0.329113924 | 0.266859886 | 0.4010152 | 0.6030534 | 0.6520096 | 0.5365 | | 23 | 0.253164557 | 0.234177215 | 0.747986666 | 0.6638655 | 0.6810345 | 0.4006453 | 0.5963 | | 24 | 0.974683544 | 0.398734177 | 0.772753829 | 0.3390558 | 0.5563380 | 0.3928489 | 0.4246 | | 25 | 0.518987342 | 0.17721519 | 0.283928837 | 0.4906832 | 0.7383178 | 0.6378130 | 0.6121 | | 26 | 0.632911392 | 0.14556962 | 0.257019463 | 0.4413408 | 0.7745098 | 0.660485 | 0.6105 | | 27 | 0.607594937 | 0.17721519 | 0.14841969 | 0.4514286 | 0.7383178 | 0.7711055 | 0.6335 | | 28 | 0.139240506 | 0.386075949 | 0.34932927 | 0.7821782 | 0.5642857 | 0.5886998 | 0.6576 | | 29 | 0.139240506 | 0.278481013 | 0.325444194 | 0.7821782 | 0.6422764 | 0.6057345 | 0.6877 | | 30 | 1 | 0.170886076 | 0.07726851 | 0.3333333 | 0.7452830 | 0.8661481 | 0.6153 |
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Table 5. Result ofexperimental data processing
| Source | Degree of freedom | Sum of square | Mean square | F | P |
|---|
| Prediction model | 14 | 0.240364 | 0.017169 | 3.91 | 0.006 | | Error | 15 | 0.065823 | 0.004388 | | | | Total | 29 | 0.306187 | | | | | Standard deviation | R2=78.50% |
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Table 6. Variance analysis of prediction model
