Z.D. Wang

Microstructure and Sliding Wear Resistance of Laser Cladded WC/Ni Composite Coatings with Different Contents of WC Particle

The aim of this article was to address the effect of WC content on the microstructure, microhardness, and sliding wear resistance of laser cladded WC/Ni composite coatings. The content of WC particle in the feed powder varied in the range of 0-80 wt.%. Experimental results showed that the laser cladded coatings exhibited homogeneous microstructure without pores or cracks. By comparing with the 45# steel substrate, the microhardness of WC/Ni composite coatings was relatively high. The microhardness of coating increased with increasing the content of WC particles. The wear resistance of WC/Ni composite coatings was strongly dependent on the content of WC particle and their microstructure. When the WC content was lower than 40 wt.% in the feed powder, the wear rate of the coatings decreased with increasing WC content. The two-body abrasive wear was identified as the main wear mechanisms. For the coatings with WC content higher than 40 wt.% in the feed powder, their wear rate increased with increasing WC content. The three-body abrasive wear and fatigue wear were the main failures. The coating with 40 wt.% WC in the feed powder exhibited the best wear resistance.

Residual stresses within oxide layers due to lateral growth strain and creep strain: Analytical modeling

Deflection test has been widely used to estimate residual stresses within an oxide layer during isothermal oxidation of one surface of an alloy or metal. Deflection models so far developed have considered elastic, plastic, and creep model to predict stresses produced from curvature of the metal/oxide interface. However, none of the models have considered growth stress. During oxidation, when new oxide forms along grain boundaries lying perpendicular to the interface, it will generate a lateral growth strain. When this strain is constrained by the underlying metal, it will generate growth stress in the oxide. This lateral growth strain combined with creep strain of the both oxide and metal will then provide the realistic approach to deal with stresses in oxide/metal composite. Considering these situations an analytical model has been developed to determine residual stresses for the metal/oxide composite of the deflection test. The stress value in both metal and oxide is calculated for notional mechanical p...

Analytical modeling of stress and strain of symmetrically oxidized metal

During high temperature isothermal oxidation, a plane of oxide molecules is inserted in each oxide grain boundary. These oxide scales grow laterally and thicken in a columnar microstructure to generate a lateral growth strain. But as the oxide scales are constrained by the underlying metal, the metal constraint produces a net in plane compressive stress in the oxide scales. To balance a compressive stress in the oxide scales, a net in plane tensile stress is generated in the metal, which results creep elongation of an oxide/metal composite. Based on this mechanism, the present paper provides a simplified modeling approach to predict an evolution of the stresses and strains in the oxide/metal composite considering the lateral growth strain of the oxide and creep strain of the metal and oxide. Oxide stress variation due to the creep properties of the oxide/metal composite such as creep indexes (m and n) and creep constants (Aox and Am) is provided for the notional mechanical properties. Oxide stress variati...

Creep-fatigue life prediction through multiple regression analyses

The aim of this paper was to propose a creep-fatigue life prediction model based on multiple regression analysis of the existing experimental data. Three different factors including temperature, hold time, and total strain range, were taken into consideration in this model. The prediction capacity of the present model was verified through comparison between predicted results and existing experimental data of different materials with different testing conditions. A good agreement was found between the predicted results and the experimental data.