| Ti/TiN/Zr/ZrN multilayer coating was deposited on1Cr17Ni2martensitic stainless steel by vacuum cathodic arc ion plating. The structure, thickness, adhesive strength and hardness of the multilayer coating were investigated by using the scanning electron microscopy (SEM), scratching tester and micro-hardness tester. Ti/TiN multilayer coating with three modulation periods was fabricated by the same preparation technics as the Ti/TiN layers of Ti/TiN/Zr/ZrN multilayer coating, and its residual stress was tested by X-ray diffraction. The effect of Ti/TiN/Zr/ZrN multilayer coating on static mechanics property and high-cycles fatigue behavior of1Cr17Ni2stainless steel was studied by tensile test and rotary bending fatigue test. The results are as follows:1. Ti/TiN/Zr/ZrN multilayer coating was flat and compact, the mean thickness is11.7μm, the hardness is2880-3492HV, and the adhesion to the substrate is56N. The residual stress of Ti/TiN multilayer coating is between-656±40and-895±62MPa.2. Yield stress, ultimate tensile stress and fatigue properties of the coated samples will be increased by applying such coating to the steel substrate, in comparison with the uncoated samples. The yield stress and ultimate tensile stress can be increased by2.34%and3.49%, respectively. The fatigue limit can be increased by11.2%(The fatigue limit of the coated samples is537MPa and the uncoated samples483MPa). The fatigue life of the steel can be increased between108and246%when the samples were tested at stresses of the order of540-650MPa.3. All the cracks initiate at the surface and at low alternating stresses the fracture process is dominated by the propagation of a single crack, whereas at high stresses many cracks can propagate simultaneously. Main reasons for the improvement in fatigue properties have been concluded that the steel surface defects can be compensated by the coating to some degree, and the coating possesses high ability to impede the initiation and propagation of the cracks because of its special microstructure and high residual compressive stress.Al coating was deposited on15CrMnMoVA steel by DC magnetron sputtering. The structure, thickness, residual stress and adhesive strength of the coating were investigated by using SEM, X-ray diffraction and tensile tester. The effect of Al coating high-cycles fatigue behavior of15CrMnMoVA steel was studied by rotary bending fatigue test. The results are as follows:1. The grains of Al coating, growing as a columnar structure, were uniform. Such coating was14.5μm in mean thickness. Its adhesion to the substrate was beyond70MPa, and its residual stress was between-113±14and-137±9MPa.2. Fatigue limit of15CrMnMoVA steel was increased by3.4%because of the application of Al coating. The fatigue limit of coated samples is701.4MPa and uncoated samples678.5MPa. But such coating has little effect on the middle fatigue life of the steel substrate.3. The fatigue cracks of uncoated samples initiate at the surface. However, the fatigue cracks of coated initiate at the boundary between the coating and substrate. Main reasons for the improvement in fatigue limit have been concluded that the steel surface defects can be compensated by the coating to some degree, and the coating possesses certain ability to impede the initiation of the cracks. |
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