Study On Joining Mechanism Of Ceramic To Metal Based On Multiple Ion Compound Diffusion Coating Alloy Technology

Ceramic materials have many excellent properties, and they were widely applied to power machine, mechanical trade, aerospace, heat exchanger, large-scale integrated circuit and electronic devices and components, etc. But because of its unavoidable disadvantage, the ceramic further extensive applications have been limited. So it is necessary to improve property of ceramic surface and join to metal into complex part, and it is the main way extending their application.This thesis has proposed the method of joining ceramic to metal based on multiple ion compounds diffusion coating alloy (MICDCA) technology. In the experiment, the complex target was used, and it was composed of multi-metal element including active elements (for instance: Ti, Zr, Hf) and other metal element (for instance: Cu, Ni, etc). The alloy-layer was directly diffusion coating on the ceramic surface by MICDCA method, and realized the alloying of the ceramic surface. The MICDCA equipment was improved and developed, the depositing alloy principle was discussed, and the technological parameter and its influence to alloy-layer composition, organization and performance were discussed.Cu-Ti, Ni-Ti binary complex target and Cu-Ni-Ti tribasic complex target structure were developed, Si3N4 structure ceramic,Al2O3 electronic ceramic and ZrO2 ceramic is compound diffusion coating by utilizing above-mentioned three complex targets implement separately. The diffusion coating alloy-layer and the combining interface were tested through optical microscopy (OM), scan electron microscope (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and scratching method.The test results testified the every elements of alloy-layer were distributed comparative uniformly; there is not obvious gathering phenomenon of composition. The diffusion coating layer makes up of interface reaction layer (diffusing layer) and surface coating layer, and the thickness of diffusion coating layer is generally 10-30um. The composition transits uniformly and continuously. The interface reaction layer consist of TiN, Ti5Si3, (Ti,Al)2O3, TiAl, Ti2O3, etc., The XRD showed the surface alloy-layer consisted of CuTi, Cu, Ni[TiO3], Ni4Ti3, Ni, etc, and this depend on the kind and structure of complex target material. Scratching method indicated the coating layer is combined better with ceramic base body, under the 100N most loads, the alloy-layer of the majority specimen were not stripped and avalanched except individual specimen.Using ordinary BAg72Cu-V brazing material, the Si3N4 ceramic with Cu-Ti diffusion coating alloy layer succeeds in joining to Q235 material and it needs not brazing flux. The liquid brazing alloy well wet and sprawl on the alloyed ceramic surface, the brazing joining interface joint well and there is not macroscopical or microcosmic defect in the joint, and the performance of resisting fracture was obviously improved.The analysis thinks the improvement of interfaces mechanics performance in ceramic/metal is based on following phenomenon and principle: (1) Th e glow ion bombard have purify and activate function on the ceramic surface, and it helps the reaction of interfaces; (2) The ion bombard can make the ceramic surfaceproduce many defects and capillary, it helps the diffusion and permeate of multi-element metal ion, especially active metallic element; (3) The diffusion of the metal ion is relatively deep, and it helps increase the thickness of interfaces reactive layer; (4) Active element Ti react to ceramic and form the compound among the metal, it plays a joining role with ceramics; Cu is not react to ceramic, it plays a increasing toughly role in interface reaction layer. (5) multi-element complex target play the ion source function, and it raise ionizing efficiency, shorten depositing time.The remaining stress of Si3N4 ceramic to Q235 brazing joint is researched by using large-scale ANSYS finite element software. Trying increase the sectional size, the equivalent remaining stress value is reduced; the thickness of brazing alloy material increases, remaining stress value drops, when reaching the best thickness lmm, the remaining stress is smaller and steadier gradually. Analyzed the remaining stress of SisN4/Q235 brazing joint with middle transition layer at the same time, the coefficient of thermal expansion and Yang mould of the middle transition layer material have influenced the jointing remaining stress. When the coefficient of thermal expansion of middle transition layer material is corresponding to ceramic, the remaining stress of interface is least value. This offers beneficial reference for project practical application that ceramic/metal joining.