Fig. 1. 30CrMnSiNi2A substrate. (a) Metallographic microstructure; (b) local magnification in Fig. 1(a)

Fig. 2. Photographs of required equipment for laser cladding and the geometric shapes and sizes of mechanical specimens for 30CrMnSiNi2A steel in laser quenching and tempering states. (a) Equipment for laser cladding; (b) impact specimens; (c) tensile specimens

Fig. 3. Macroscopic morphology in the cross section of 30CrMnSiNi2A substrates under multiple cladding 30CrMnSiA coating. (a) 1 layer; (b) 2 layers; (c) 3 layers; (d) 4 layers; (e) 5 layers; (f) 6 layers; (e) 7 layers; (e) 8 layers

Fig. 4. Microstructures of laser quenching zone in the 30CrMnSiNi2A substrate (located in Fig. 3). (a) 1 layer, A1 zone; (b) 2 layers, A2 zone; (c) 3 layers, A3 zone; (d) 4 layers, A4 zone; (e) 5 layers, A5 zone; (f) 6 layers, A6 zone; (g) 7 layers, A7 zone; (h) 8 layers, A8 zone

Fig. 5. Microstructures of high temperature tempering zone in the 30CrMnSiNi2A substrate (located in Fig. 3). (a) B1 zone; (b) B2 zone; (c) B3 zone; (d) B4 zone; (e) B5 zone; (f) B6 zone; (e) B7 zone; (e) B8 zone

Fig. 6. Microstructures of partial tempering zone in the 30CrMnSiNi2A substrate (located at C1--C2 of each coating in Fig. 3). (a) C1 zone; (b) C2 zone; (c) C3 zone; (d) C4 zone; (e) C5 zone; (f) C6 zone; (e) C7 zone; (e) C8 zone

Fig. 7. Tensile properties of 30CrMnSiNi2A substrate with HAZ (1 layer to 8 layers) and 30CrMnSiNi2A substrate

Fig. 8. Initiation fracture position of tensile specimens in HAZ of the 30CrMnSiNi2A substrate. (a) High temperature tempering zone (HTTZ) in 1 cladding layer; (b) HTTZ in 2 cladding layers; (c) HTTZ in 3 cladding layers; (d) HTTZ in 4 cladding layers; (e) HTTZ in 5 cladding layers; (f) HTTZ in 6 cladding layers+partial tempering zone (TZ); (g) incomplete quenching zone (IQZ) in 7 cladding layers+HTTZ in 6th-cladding layer; (h) HTTZ of 7th-cladding layer in 8 cladding layers

Fig. 9. Fracture morphology of the tensile specimens of the 30CrMnSiNi2A substrate with HAZ after multiple layer cladding. (a) Macro-morphology of the fracture for 1 cladding layer; (b) crack initiation zone and (c) crack growth zone are shown in Fig. 9(a); (d) macro-morphology of the fracture for 2 cladding layers; (e) crack initiation zone and (f) crack growth zone are shown in Fig. 9(d); (g) macro-morphology of the fracture for 7 cladding layers; (h) crack initiation zone and (i) crack growth zone are shown in Fig. 9 (g); (j) macro-morphology of the fracture for 8 cladding layers; (k) crack initiation zone and (l) crack growth zone are shown in Fig. 9(j)

Fig. 10. Impact toughness of HAZ in 30CrMnSiNi2A substrate according to different cladding layers