Mikio Yoneyama

Dynamic observation of formation process in laser cladding using high speed video camera

Formation phenomena of cladding layers were observed with high speed video camera to analyze the cladding layer formation process. The influence of the overlap rate and laser beam profile were also investigated on formation process of cladding layer. High speed video revealed that the bottom of the laser beam having low power intensity melted only powder material without melting the substrate and gathered powder to be a globular shape. This caused the lack of powder material, melting of the substrate and mixing substrate to cladding layer by the following laser irradiation. The gathering of powder material was suppressed by using a copper slit to shape laser beam profile. It was found that the laser beam profile strongly affected the laser cladding process.

Influence of laser parameters on hardness of the Ni-Cr-B-Si cladding layer

Laser cladding is one of the useful surface coating methods for improving the quality of wear and corrosion resistance of material surface. Compared with other conventional surface coating methods, such as thermal spray and plasma transferred arc welding (PTA), laser cladding can produce much better coatings with minimum dilution and well bond to the substrate. Ni-Cr-Si-B alloy is widely used as a hard facing material. However hardness of this layer produced by PTA is decreased due to dilution. In this study, we investigated the influence of power density and heat input on hardness of the Ni-Cr-Si-B alloy layer. We revealed the combination of laser parameters which can produce cladding layer with Ra of under 8 μ m and upper the hardness of 820 HV.Laser cladding is one of the useful surface coating methods for improving the quality of wear and corrosion resistance of material surface. Compared with other conventional surface coating methods, such as thermal spray and plasma transferred arc welding (PTA), laser cladding can produce much better coatings with minimum dilution and well bond to the substrate. Ni-Cr-Si-B alloy is widely used as a hard facing material. However hardness of this layer produced by PTA is decreased due to dilution. In this study, we investigated the influence of power density and heat input on hardness of the Ni-Cr-Si-B alloy layer. We revealed the combination of laser parameters which can produce cladding layer with Ra of under 8 μ m and upper the hardness of 820 HV.

Experimental analysis of the influence of beam profile on cladding layer formation phenomena

In order to investigate the influence of beam profile on laser cladding phenomena, Ni-Cr-Si-B alloy coating was produced on type 304 stainless steel plate with two types of beam profile, Gaussian-like and flat-top type. High speed observation revealed that Gaussian-like beam profile generated the droplets near the molten pool. These droplets caused the rough cladding layer. Droplets were not generated by using flat-top beam profile. These droplets caused the rough cladding layer. Flat-top beam profile suppressed the droplets formation and smooth cladding layer was produced.In order to investigate the influence of beam profile on laser cladding phenomena, Ni-Cr-Si-B alloy coating was produced on type 304 stainless steel plate with two types of beam profile, Gaussian-like and flat-top type. High speed observation revealed that Gaussian-like beam profile generated the droplets near the molten pool. These droplets caused the rough cladding layer. Droplets were not generated by using flat-top beam profile. These droplets caused the rough cladding layer. Flat-top beam profile suppressed the droplets formation and smooth cladding layer was produced.