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Study On Technique Of Powder-Feeding Laser Cladding Adulterating Composite Coating With Ceramic And Forming Mechanism Of Coating

Posted on:2003-11-20Degree:DoctorType:Dissertation
Country:ChinaCandidate:S C ZhangFull Text:PDF
GTID:1101360065956117Subject:Condensed matter physics
Abstract/Summary:PDF Full Text Request
Laser cladding is used to forming a kind of surface coating ,which has good metallurgical bonded properties between coating material and substrate ,and no gas hole and crackle , making use of high energy laser beam to melt coating material and a thin layer base metal .It has been becoming one of new techniques that having infinite development future and characteristic very much in the modern surface technique system , and bigger application foreground in "remanufacturing engineering in 21st century ".Laser cladding technique mainly involved in two aspects: 1 , design about material system of cladding coating ; 2 , constituting about cladding technological criterion . In material system , the study on laser cladding adulterating auto-melting alloy coating with ceramic has been one of forepart hotspot in these field such as metal material surface strengthening and modifying . By investigation on properties of celerity melting and solidification in laser cladding process or application attributes of cladding modified coating , author considers that the matter of material system design of laser cladding is to resolve the anti-wear design problem on tribological system , therefore , the design principle and method of laser cladding anti-wear composite material based on tribological system knowledge was put forward for the first time , and the blindness problem , which it has existed all time in the material design or electing , was settled on the methodology.Having Based on that principle , and associated it with auto-feeding laser cladding model that had best adaptability in production , author has designed a series of different material that adulterated Ni base auto-melt alloy with the WC enwrapped by metal Ni; For studying how to control crackle of cladding layer brought by thermal stress , the material system that ZrOi was intermingled with Ni base auto-melt alloy was firstly put forward and design . So , 58 or 36 kinds of cladding technics criterion , which were respectively applied to the material of adulterating with WC or ZrCh , at one time ,overlapping laser cladding were bring into effect in according to surface quality of cladding layer . By comparing of surface quality or microstructure or microhardness and its distributing on the cross section , better technique criterion of laser cladding were achieved in the different material system . Then , the material anti-wear properties were assessed by the Ring-block Frication & Wear Tester , and wear mechanism of two kinds material were analysed . The results of these experimentation showed that ceramic phase counteracted crackle production on the surface of composite coating , thereby it presented non-continuous wear trace ; the coating of containing WC particle belonged to the style of hard- phase bearing weight, but of containing ZrO2 particle peeled off.The modern surface analyse technique such as XRD or SEM and EDS were applied to investigate phase structure and micro-section and element distributing states of some cladding layer , the results had made know : 1, The cladding coating of adulterating auto-melting alloy with WC formed the symmetrical dispersion structure , and the surface of WC block was consisted of eutectic structure (WC+W2C) ; 2, In the cladding coating of containing ZrO2, the enrichment phenomenon of Cr element on the surface of ZrO2 ceramic particles occurred , so, the crystal form that ZrO2 particles were enwrapped by Cr came forth in laser cladding coating . At the same time , it indicated that crystal type of ZrO2 was not cubic type (t) that had to form under fast solidification , on the contrary , it became monotype (m) due to effect of thermal stress . so it does , the design aim , which the toughness of laser cladding coating were increased by phase transformation , was carried out. 3, The interface or transition area between cladding layer and substrate could gained the solid solution structure of Fe-Ni and Fe-Cr , which could markedly raised metallurgical concatenate intensity .The physical models about figuration...
Keywords/Search Tags:powder-feeding laser cladding, adulterating with ceramic, composite Coating design, forming mechanism, abrasion wear
PDF Full Text Request
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