【摘要】：本文以工作環(huán)境惡劣的柱塞泵活塞的使用為背景,探究利用激光熔覆技術改善柱塞泵活塞工作表面的耐磨損和耐腐蝕性能,應用ANSYS仿真軟件對激光熔覆這一復雜過程的溫度場進行數(shù)值模擬及分析,利用激光熔覆技術在柱塞泵活塞所用材質(zhì)45鋼表面制備具有不同配比的Ni60+TiC復合涂層,并研究各涂層的組織形貌、顯微硬度、耐磨損以及耐腐蝕性能。研究表明,激光熔覆是材料快速熔化并且凝固的過程,激光熔覆過程的溫度場是一個有規(guī)律的準穩(wěn)態(tài)溫度場,確定了最佳的激光熔覆工藝參數(shù)。不同配比制備的激光熔覆涂層表面有差異,激光熔覆單一Ni60涂層表面較為平整致密,而Ni60+TiC熔覆涂層表面有顆粒狀的凸起,且Ni60+10%TiC涂層表面有少許孔洞。激光熔覆涂層的表面硬度與基體相比明顯提升,Ni60+TiC復合涂層硬度高于單一Ni60涂層,并且隨著TiC添加量的增多,涂層的顯微硬度也逐漸升高。激光熔覆涂層的摩擦系數(shù)與基體45鋼對比有大幅度的降低,Ni60+TiC復合涂層比單一Ni60涂層摩擦系數(shù)更小,而且Ni60+20%TiC復合涂層的摩擦系數(shù)達到最佳。各激光熔覆涂層的磨損率均比基體要低,Ni60+TiC復合涂層的磨損率比單一Ni60涂層更低,Ni60+20%TiC涂層的磨損率達到最低。激光熔覆Ni60+TiC復合涂層比單一Ni60涂層的耐磨性更好,能夠明顯地提高45鋼基體的耐磨性,并且熔覆材料在Ni60+20%TiC比例下,涂層耐磨性最佳。45鋼基體的磨損機理以犁削為主,而激光熔覆涂層磨損機制為犁削與疲勞剝落綜合作用,隨著TiC添加量的增多,涂層表面犁削作用逐漸減弱,疲勞剝落逐漸增多。激光熔覆涂層的耐腐蝕性能明顯強于基體45鋼,并且Ni60+20%TiC復合涂層與Ni60+30%TiC復合涂層耐腐蝕性能比單一Ni60涂層更為優(yōu)越。在激光熔覆過程中,高能量激光的照射使熔覆粉末完全熔融,掃描后熔融的材料迅速凝固,這種快速熔凝以及高溫度熔池內(nèi)的強烈對流,使得熔覆涂層具備均勻分布的硬質(zhì)相顆粒以及細致均勻的組織結(jié)構(gòu),這些熔覆層的內(nèi)部典型特征對于耐磨性和耐腐蝕性能的改善具有顯著作用。
[Abstract]:Based on the use of piston in poor working environment, this paper explores how to improve the wear and corrosion resistance of piston surface by laser cladding technology. The temperature field of laser cladding is numerically simulated and analyzed by using ANSYS software. The composite coating with different ratio of Ni60 TiC is prepared on 45 steel surface of piston by laser cladding. The microstructure, microhardness, wear resistance and corrosion resistance of the coatings were studied. The results show that laser cladding is a rapid melting and solidifying process of materials, and the temperature field of laser cladding is a regular quasi-steady temperature field. The optimum technological parameters of laser cladding are determined. The surface of laser cladding coating prepared by different ratio is different. The surface of laser cladding single Ni60 coating is flat and compact, while the surface of Ni60 TiC cladding coating has granular protrusions, and there are a few holes on Ni60 10%TiC coating surface. The surface hardness of the laser cladding coating is obviously higher than that of the substrate, and the hardness of the Ni60 TiC composite coating is higher than that of the single Ni60 coating, and with the increase of the amount of TiC, the microhardness of the coating increases gradually. The friction coefficient of laser cladding coating is much lower than that of 45 steel substrate. The friction coefficient of Ni60 TiC composite coating is smaller than that of single Ni60 coating, and the friction coefficient of Ni60 20%TiC composite coating is the best. The wear rate of each laser cladding coating is lower than that of substrate, the wear rate of Ni60 TiC composite coating is lower than that of single Ni60 coating, and the wear rate of Ni60 20%TiC coating is the lowest. The wear resistance of laser cladding Ni60 TiC composite coating is better than that of single Ni60 coating, which can obviously improve the wear resistance of 45 steel substrate, and the wear resistance of the cladding material is the best under the Ni60 20%TiC ratio. The wear mechanism of 45 steel substrate is mainly ploughing. The wear mechanism of laser cladding coating is the combination of ploughing and fatigue spalling. With the increase of TiC content, the ploughing effect of the coating surface decreases gradually, and the fatigue spalling increases gradually. The corrosion resistance of laser cladding coating is obviously better than that of 45 steel substrate, and the corrosion resistance of Ni60 20%TiC composite coating and Ni60 30%TiC composite coating is better than that of single Ni60 coating. During laser cladding, high energy laser irradiation completely melts the cladding powder, solidifies the melted material rapidly after scanning, and the strong convection in the melting pool at high temperature. The cladding coating has a uniform distribution of hard phase particles and fine and uniform microstructure. These typical internal characteristics of the cladding coating play an important role in improving the wear resistance and corrosion resistance of the cladding coating.
【學位授予單位】：濟南大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG174.4

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