AZ91D镁合金表面激光熔覆Al-TiC涂层组织和性能的研究

目的研究Al-TiC涂层组织和性能的特性,以提高镁合金涂层的硬度和耐蚀性能。方法采用Nd:YAG固体激光器,在AZ91D镁合金表面通过激光熔覆制备Al-TiC涂层,采用光学显微镜、X射线衍射仪、显微硬度计、电化学工作站,对熔覆层的组织形貌、物相结构、显微硬度和耐蚀性能进行测定和分析。结果 Al-TiC涂层的主要组成相有AlTi_3(C,N)_(0.6),Al_3Mg_2,Mg_2Al_3,Al和TiC等。激光熔覆层的厚度约为0.35 mm,表面成型良好,结合层晶粒细小,熔覆层与镁合金基体之间结合良好,呈大波浪形。熔覆层试样的平均显微硬度为224HV,约为基体显微硬度(62HV)的4倍,由此表明熔覆层对镁合金硬度有明显的增强作用。镁合金基体的自腐蚀电位为-1.475 V,自腐蚀电流密度为7.556×10~(–5) A/cm~2,熔覆层试样的自腐蚀电位为-1.138V,自腐蚀电流密度为4.828×10~(–5) A/cm~2,与镁合金基体相比,熔覆层的腐蚀电位值增加,腐蚀电流密度值变小,熔覆层的耐蚀性能得到提高。结论采用激光熔覆技术,能够在AZ91D镁合金基体表面制备Al-TiC涂层,由于硬质相AlTi_3(C,N)_(0.6),Al_3Mg_2,Mg_2Al_3,TiC等的存在,熔覆层的显微硬度和耐蚀性能显著提高。

Microstructure and Properties of Laser Cladding Al-TiC Coating on AZ91D Magnesium Alloy

In order to improve micro-hardness and corrosion resistance of magnesium alloy coating by studying the charac-teristics of microstructure and properties of Al-TiC coating. Al-TiC laser cladding layer on AZ91D magnesium alloy was pre-pared by using Nd: YAG solid laser. Microstructure morphology, phase structure, micro-hardness and corrosion resistance of the cladding layer were investigated with the aid of optical microscope (OM), X-ray diffraction (XRD) measurement, mi-cro-hardness tester and electrochemical workstation. It can be seen that the Al-TiC coating were mainly composed of Al- Ti3(C,N)0.6, Al3Mg2, Mg2Al3, Al, TiC, etc. The thickness of the laser cladding layer was about 0.35 mm. The surface of laser cladding was well formed, and the grain size of the interface layer was refined. There was a good bond between the Al-TiC coating and the substrate, and it presented the shape of a big wave. The average micro-hardness of cladding layer sample was 224 HV, which was about four times of the matrix micro-hardness (62 HV), thus indicating that Al-TiC coating had significant potentiation to AZ91D magnesium alloy. The self-corrosion potential of magnesium alloy substrate was-1.475 V. Its current density of self-corrosion was 7.556×10–5 A/cm2. The self-corrosion potential of the cladding layer sample was-1.138 V. And the current density of self-corrosion was 4.828×10–5 A/cm2. Compared with the magnesium alloy substrate, corrosion potential value of the cladding layer increased, the corrosion current density value decreased and the corrosion resistance of cladding layer could be improved. Using laser cladding technology can prepare Al-TiC coating on AZ91D magnesium alloy. Since the existence of hard phase AlTi3(C,N)0.6, Al3Mg2, Mg2Al3, TiC, etc., micro-hardness and corrosion resistance of cladding layer can be increased dramatically.