Study On Crack Defects Of High Carbon And High Chromium Surfacing And Surfacing Layer

Surfacing layer that formed by high carbon high chromium wire is easy to appear the crack, the serious crack will threat the overall safety of surfacing layer, this paper mainly studies when the high carbon high chromium wear-resistant was welded on Q235B low carbon steel、45medium carbon steel、Q345A low alloy steel,the relationship between welding parameters and cracks on the surfacing layer.Observing the external cracks and X-ray flaw analyse macro cracks on the surfacing layer, when the test material at different welding parameters and substrate conditions, analysed morphology, distribution, quantity, size of micro cracks through metallurgical. The results show that cracks on the surfacing layer are transverse crack, when the welding line energy is change, the macroscopic crack morphology would changes, the larger the width of the crack when welding energy is larger, with welding line energy is changes, the shape, distribution, quantity, size of micro cracks is changes, the phenomenon is appeared that crack extend into the substrate or along the fusion zone when welding energy was very small.The phase of the surfacing layer was analyzed by X-ray diffraction and show: when welding process is different, the kind of phase is different, the main phases are austenite, carbide of Cr7C3, Fe-Cr solid solution.Welding stress is related to the type of internal organization after welding, the effect of welding thermal cycle, differences in tissue morphology would affects the welding residual stress of surfacing layer and heat affected zone, crack formation would be influenced in the surfacing layer and heat affected zone..The macro hardness and micro hardness test was made on surfacing layer, the results showed that:when the welding line energy was smaller, the hardness of microstructure was increased, the relationship between hardness of organization surfacing layer fusion zone and welding cracks is researched. The results showed that the hardness of the fusion zone was higher, in the role of welding residual stress, the cracking would trend to increase. In order to test the safety of specimen in the actual production work, the experiment was done on the test piece, the results show:the decreases of welding line energy would increases the wear resistance.but the phenomenon of surfacing layer peeled was appeared, analysed spalling fracture morphology surface of surfacing layer by the SEM, the type of welding layer crack was low plastic hardening. The crack was produced by low plasticity and high hardness、micro cracks plus the impact stress and welding residual stress and other factors.The welding residual stress is an important factor of affecting the region and thermal crack. In this paper, the temperature field and the stress field of welding process was simulated by ANSYS software., the change of welding line energy will affect the distribution of temperature field and stress field, the change of welding line energy will change the figure stress field and discuss the relationship between the temperature field%the stress field and crack, the welding preheating is simulated.