Microstructures and High-Temperature Friction and Wear Properties of Laser Cladded Fe-Ni-Cr Gradient Composite Coating for Brake Disc

Fig. 6. Microstructures of each part of gradient coating. (a) Whole view of cross-section; (b) enlarged area A；(c) enlarged area B; (d) enlarged area C

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$TEM morphologies of heat-affected zone. (a) TEM morphology at low magnification; (b) TEM morphology at high magnification; (c) selected area electron diffraction (SAED) of region 1; (d) SAED of region 2$

Fig. 7. TEM morphologies of heat-affected zone. (a) TEM morphology at low magnification; (b) TEM morphology at high magnification; (c) selected area electron diffraction (SAED) of region 1; (d) SAED of region 2

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Fig. 8. Element distribution of coating cross-section by linear sweep

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Fig. 9. Microhardness of coating cross-section

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Fig. 10. Friction coefficient of substrate and coating at different temperatures. (a) Substrate; (b) coating

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Fig. 11. Volume loss of substrate and coating at different temperatures

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Fig. 12. Wear appearances of substrate at different temperatures. (a) RT; (b) 100 ℃；(c) 200 ℃；(d) 300 ℃

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Fig. 13. Schematics of wear mechanism. (a) Early wear; (b) abrasive wear; (c) adhesive wear; (d) oxidative wear

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Fig. 14. Wear appearances of coating at different temperatures. (a) RT; (b) 100 ℃；(c) 200 ℃；(d) 300 ℃

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Fig. 15. Cross-section microstructures of coating after high temperature friction and wear test. (a) 200 ℃；(b) 300 ℃

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Table 1. Main chemical composition of gray cast iron and cladding powder
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Table 1. Main chemical composition of gray cast iron and cladding powder
Material Mass fraction/%
C Si B W Mn Cr Ni Fe
Gray cast iron 3.4 2.2 - - 0.7 - - Bal.
Cladding powder ≤1.4 1.6-2.4 ≤1.2 ≤1.5 - 18-20 30-33 Bal.

Table 2. Technological parameters of laser cladding test
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Table 2. Technological parameters of laser cladding test
Parameter Value
Laser power /W 900
Sweep speed /(mm·min^－1) 300
Powder feed rate /(L·min^－1) 6.5
Gas flow/(L·min^－1) 9
Spot diameter /mm 1
Overlap rate /% 75

Table 3. Friction and wear test parameters
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Table 3. Friction and wear test parameters
Parameter Value
Load force /N 75
Rotating speed /(r·min^－1) 860
Resolution ratio /mN 30
Test duration /s 1800
Temperature /℃ RT，100，200，300

Table 4. Parallel quantitative calculation results of phases

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Table 4. Parallel quantitative calculation results of phases

Phase	Mass fraction /%	Relative standard deviation /%
Fe₃C at the bottom of coating	63.7，59.2，56.7	5.9
Fe₃C at the middle of coating	20.4，24.2，23.1	8.7
Fe₅C₂ at the middle of coating	22.5，23.1，19.8	8.0
Fe₅C₂ at the surface of coating	17.5，15.9，16.3	5.0
Cr₇C₃ at the middle of coating	12.9，14.1，15.2	8.2
Cr₇C₃ at the surface of coating	21.8，21.1，18.6	8.2

Table 5. EDS analysis of worn substrate surface
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Table 5. EDS analysis of worn substrate surface
Area Mass fraction of elements/%
Fe C O
A 79.7 4.6 12.8
B 69.1 7.8 18.7
C 59.9 10.6 26.4
D 33.5 8.6 55.4
E 51.6 2.8 42.6
F 42.3 2.4 52.4
G 37.9 3.1 56.8
H 70.4 4.4 19.9

Table 6. EDS analysis of coating wear surface
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Table 6. EDS analysis of coating wear surface
Area Mass fraction of elements/%
Fe C O Cr
A 43.6 26.9 8.8
B 53.9 7.2 11.6
C 41.8 2.5 14.6 16.5
D 28.1 1.2 62.9 2.8
E 29.2 1.5 57.5 5.1
F 33.2 1.7 62.1 2.9
G 32.7 2.5 37.6 5.7
H 34.1 1.3 54.6

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Xiaoyu Shi, Daosheng Wen, Shouren Wang, Gaoqi Wang, Mingyuan Zhang. Microstructures and High-Temperature Friction and Wear Properties of Laser Cladded Fe-Ni-Cr Gradient Composite Coating for Brake Disc[J]. Chinese Journal of Lasers, 2022, 49(2): 0202017

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