Study On Morphology And Strength Of Alumina Thin-wall Parts In Single-track By Direct Material Deposition

Alumina ceramic is one kind of the ceramic materials used widely because of its excellent performances. But traditional processing methods are complex, time and money consuming, which restrict the development of ceramic products. Direct material deposition technology shows a great application prospect and develops rapidly for its overcoming the drawback of traditional method. Alumina powder was used in the paper as research object. Thin-wall parts was formed by the method of direct material deposition. The morphological characteristics and color of the thin-wall parts strength is studied. At the same time, four kinds of substrate, light-powder coupling, three-point bending strength, macro structure is analyzed in order to achieve high quality alumina based on laser near net shaping molding.First of all, image processing method was used to analysis powder beam field image. Powder beam focal spot diameter and the focal length of 3.4 mm and 1 4.7 mm was get respectively. Four kinds of substrate are analyzed. It is found that the dense alumina ceramic substrate is prone to cracking during molding, and molding quality of the thin-wall parts is poor. Porous alumina ceramic substrate and zirconia ceramic substrates are prone to pitting, which can promote forming and has the effect of the cracking resistance. The pitting phenomenon is avoided by TC4 titanium alloy, and the forming quality is better.Secondly, the relationship between the morphology, bending strength and process factors is analyzed. Laser power influence the fracture morphology: low and high laser power affect the top morphology and fracture defects, respectively. Scanning speed affects the cross section, top morphology, profile and crack. Scanning speed and feeding rate affect the parts color. In the process of forming, the phenomenon of oxidizing reaction of TC4 titanium alloy substrate, generating Ti O 2 stain, makes the thin-walled part black or brown. In the bending strength tests of alumina, it is found that three-point bending strength of the thin wall parts increases with the increase of laser power and reduce later. And it increases with the increase of scanning speed. When the speed is more than 3 mm/s, flexure strength decreased slightly. The bending strength increases with the increase of the feeding rate, finally no longer change s. Finally the bending strength between the average temperature of molten pool is analyzed. It is found that blending strength increases and then decreases with the average temperature of molten pool. When the average temperature of the molten pool is in the range of 2194-2365 ℃, the bending strength is the highest.