Three kinds of coatings had been prepared on the surface of 45CrNi steel plates using laser cladded technique by adding Mo and CeO2 into the Nickel-based alloys. The wear behaviors of these three kinds of coatings in sliding against Al2O3 grinding ring were investigated by using a MM-200 Wear Tester. The results indicated that the addition of both Mo and CeO2 could improve the wear resistance of Nickel-based alloy coatings. If the original Nickel-based alloy coating was taken as the standard sample, the relative wear resistances of Mo-modified and Ce-modified coatings are 1.31 and 7.54 respectively, and the coefficients of friction appreciably decreased. SEM images of the worn surface of the coatings showed that the wear of original Nickel-based alloy coating was dominated by the mechanism of micro-cutting, and the Mo-modified coating and Ce-modified coating had a feature of fatigue wear in addition to micro-cutting. In sliding, the wearing resistance of Ce-modified coating was higher than the other two. The wear test results were closely related to the microstructures of the coatings.
The tensile plastic strains and the residual tensile stresses caused by heat input during the laser cladding process are the main reasons for the cracking. In this paper, the laser cladding process on a type 1045 steel plate with Ni60 powder feeding was investigated and simulated by finite element method to analyze the temperature field and stress-strain field of the laser cladding process. In the temperature field model, the main considerations were given to the heat source data and the thermal boundary conditions. The interactions of laser, powders and base metal were mainly considered in the application of the heat source data. The relationship between the heat convection coefficient of work piece surface and the temperature variation was mainly considered in the application of thermal boundary conditions. In the stress-strain field model, the main consideration was given to the elastic-plastic characteristics of the materials, and the materials were assumed to be linear strain-strengthened. Moreover, the thermal stresses could be solved through the temperature field and were subsequently applied directly to the stress-strain field model as loads. Besides the temperature variations, the stress variations and the strain variations of some critical points (including the crest point of the cladded layer and intersection point of cladded layer and plate) were also obtained through the finite calculation. The temperature variations show that the heating curve is approximately a straight line while the cooling curve is like an arm of a hyperbola. The strain variations show that the thermal strain has a variation trend similar to the temperature variations. The elastic strain of each point is very low when compared to the plastic strain. The calculated results show that the tensile plastic strain of the crest point on the coating is the greatest in the cladding direction and the tensile stress in this direction of this point is great too. As a result, transverse crack can be easily initiated at the crest of the coating. While the tensile plastic strain at the intersection point of the base metal and coating is the greatest in the direction vertical to the plate thickness, the stress at this point (in the same direction) is compressive. Therefore, the intersection points tend to form a limited toe crack which can not grow.
An experimental investigation of ac pulsed argon arc welding of the ZL105 alloy was carried out under the condition of existed the defects of the high temperature, the thermal deformation. The surface morphology, microstructure and temperature field of the surfacing layers were investigated. The results showed that the heat accumulation of squitter pulsed welding was less, and with smaller HAZ, crystal grains were thinner in the same conditions. Compared with argon arc welding, the energy of squitter pulse argon arc welding acted on the matrix was less but more centralized, the whole HAZ temperature raised slowly.
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