Study On The Basic Process Of Preparing Bioceramic Coatings By Laser Cladding

Laser cladding is the use of high-energy,high-density laser beam to melt the powder and form a metallurgical bonding surface on the surface of the substrate.As a surface modification technology,it has been widely used.Bio-ceramics are stable because of their physical and chemical properties,and they have good biological activity and biocompatibility.It has become a research hotspot to use laser cladding to prepare a layer of bio-ceramic coating on the metal surface.In this paper,the laser cladding technology of HA was synthesized in situ by using CaHPO₄·2H₂O and CaCO₃ mixed powders as raw materials and powders were preset.The laser power,scanning speed,focal length and other process parameters are the key factors affecting the surface composition and molding quality of the coating.Through XRD analysis,the surface composition of the coating was analyzed.With the increase of laser power and scanning speed,the content of HA on the coating surface increased first and then decreased.With the increase of focal length,the change of HA on the coating surface was not obvious.Temperature is the main factor affecting the formation of HA on the coating surface.The ideal temperature for generating HA is between 800 and 1200 degrees.Because the bath temperature cannot be measured directly,the temperature of the bath is measured by experiments and numerical simulations.Finally,the effect of the scanning speed>laser power>focal length on the temperature is obtained.By further optimizing the process parameters through orthogonal experiments,it was found that the HA component produced on the coating surface was more when the laser power,scanning speed and focal length were:500w,7mm/s,30mm and 400w,5mm/s,and40mm,respectively.The content of HA after cladding varies with the ratio of powders.Finally,when the ratio of Ca/P is 1.8,the HA content of the coating surface is the highest.In order to prepare the multi-channel single-layer HA coating with narrower surface cladding width,deeper penetration,and higher bonding strength,a good surface morphology of the coating is controlled by selecting a reasonable process parameter.Finally,when the power is 300w,the scanning speed is 9mm/s,and the focal distance is 25mm,the coating surface is good,and there are no defects such as coating cracking and peeling.Based on the single-factor experimental rule,a bioceramic coating was prepared on the surface of a titanium alloy.At a laser power of 400 W,a scanning speed of 5 mm/s,and a focal length of 30 mm,the coating surface was relatively smooth,and the average Rockwell hardness was 67 HRC.Then,the longitudinal microhardness test showed that the maximum value was 1127 HRC in the bond area between the substrate and the coating.Finally,the biological properties of the coating were studied,and the final coating surface had good biocompatibility.