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The Study Of Controlling Cracks In Laser Clad Layer

Posted on:2008-10-21Degree:DoctorType:Dissertation
Country:ChinaCandidate:H D MaoFull Text:PDF
GTID:1101360272985423Subject:Mechanical Manufacturing and Automation
Abstract/Summary:PDF Full Text Request
The laser cladding technology is more available, practical and flexible than other surface working methods. But the cracks exist in cladding layer reduce the performance and make it hard to become widespread available.Plentiful experiments about the crack in laser cladding process are performed in this dissertation. The control method of cladding crack is studied under the condition that the substrate is not preliminary heated and the transient layer is not designed. Some experiment studies are made about the crack detection in cladding process, the configuration of cladding material and the development of cladding techniques. The research results reach the requirement of industrial application within a certain scope. The following contributions were made.By use of the acoustic emission detective technique, the generation and development of crack in cladding process are in-situ measured. The number of crack with different cladding material are measured, meanwhile, the position of crack is detected. Considering the generation time and the temperature of cladding process calculated by finite element method, the temperature scope of crack generation is analyzed. It can be concluded that the most cracks in cladding layer is cold-crack.Configure iron-based alloy that is utilized in laser cladding process and make a test of the structure and characteristics of the cladding layer. It is found that iron-based alloy cladding layer can be well metallurgicly combined with the substrate, and the cladding layer is mainly composed of the substrate of martensite and remaining austenite and the primary and secondary dendrite of various compounds that are made from C, B and Si or Fe and Cr. Compared with the quenching substrate, the wear characteristic is improved greatly.Considering the crack of cladding layer, the method of adding softening band to the cladding layer is put forward, and it aims at making the stress softening and reducing the thermal stress of cladding layer to reduce the cladding crack. The influence to the cladding crack caused by adding stainless steel meshwork to cladding layer as the stress absorption band is studied.The function of ceramal phase in cladding layer is analysed, and the valuable conclusion that the WC at raw condition could induce stress concentration at sharp corners,can be get by analyzing the different contributions of Ni-WC and pure WC to cracks of cladding layer.By using the research results, the booster pump shaft that is repaired has been operating for over two years in Tianjin Petrochemical Company Chemical Fiber Plant. It can steadily operate for a long time, and huge economic benefits have been achieved.The outcome of this dissertation can not only provided a new method for measuring and controlling of the cladding crack, but also be valuable for relative research.
Keywords/Search Tags:Laser cladding, cladding layer, crack, acoustic emission detective technique, stainless steel meshwork, booster pump shaft
PDF Full Text Request
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