Showing 4 results for Microhardness
N. Rahimi, T. Saed,
Volume 5, Issue 2 (1-2020)
Abstract
In this study the effect of activating fluxes on the penetration depth, microstructure and microhardness of AISI316L austenitic stainless steel were evaluated by three TIG process variations (TIG, A-TIG and FB-TIG) and the results were compared together.. After selecting the optimal flux in the second stage, the effect of that on the penetration depth, microstructure and weld microhardness of welded 316L austenitic stainless steel by A–TIG and FB-TIG methods, were evaluated and the results were compared by the sample which was welded by TIG process. At this stage, it was found that the depth and width to depth ratio in FB-TIG method is slightly greater than the other two methods. Also in FB-TIG method, eqiaxed dendritic zone in the center line of weld is slightly greater than in A-TIG method. Study of microhardness of weld in three methods shows that in A-TIG and FB-TIG methods hardness of center line is more than TIG method.
A. Ghandi, M. Shamanian, M. R. Salmani3,
Volume 6, Issue 1 (8-2020)
Abstract
The structural and hardness developed in advanced high-strength steel DP590 have been investigated with the help of optical microscopy and scanning electron microscopy on resistance spot welded specimens. The hardness diagram of the weld sections was prepared by microhardness test and the temperature peak and heat distribution were simulated by menas of the Abaqus software. The results show that according to the temperature generated in each region of the weld nugget, the HAZ and base metals have different microstructures, and these difference affects the hardness of the regions. The presence of tempered martensite islands with a fraction of 44% in ferrite matrix in base metal, mainly martensitic structure in the nugget, and martensitic structure along with scattered areas of ferrite in the HAZ was observed. The results of the microhardness tests showed difference in hardness values of the regions, and also it was observed that the hardness values increased in the HAZ and weld zone. The hardness values measured in the nugget, base metal, and HAZ were around 400, 200, and 450 HV which were in accordance with the observed structures
Mojtaba Vakili-Azghandi, Ali Shirazi,
Volume 7, Issue 1 (8-2021)
Abstract
The results showed that the microhardness and tensile strength of the heat-affected zone as the weakest welding zone in some samples reduced up to 30% compared to the base metal. On the other hand, a decrease in rotational speed, an increase in tool movement speed, and the number of welding passes cause grain refinement and improve mechanical properties. However, the effect of decreasing the rotation speed and increasing the tool movement speed were shown to be more favorable due to less heat production. Accordingly, the hardness in the welded zone with a rotational speed of 600 rpm and a movement of 80 mm/min increased from 90 to 125 HV compared to the base metal, and the hardness reduction in the zones around the welded zone was only 5 Vickers. It was also found that reducing the grain size of the stir zone, while improving the mechanical properties leads to increasing the density of the surface pasive layer, preventing the attack of aggressive chlorine ions and thus reducing the corrosion intensity by 50 times in saline seawater.
M.r. Borhani, S.r. Shoja Razavi, F. Kermani, M. Erfan Manesh, S.m. Barekat, H. Naderi Samani, M. Shahsavari,
Volume 8, Issue 2 (1-2023)
Abstract
The purpose of this research is to laser cladding of stellite6 and stainless steel 17-4PH powders on the substrate of stainless steel 17-4PH, and investigate its solidification microstructure. The results showed that the microstructure of the stellite6 cladding has a cobalt solid solution ground phase with an FCC structure and Cr7C3 and Cr23C6 carbides. Also, the values of the primary dendrite distance and the distance of the secondary dendrite arm have decreased by moving away from the interface; The reason for this is related to the difference in the cooling rate in different parts of the coating. The microstructure of 17-4PH stainless steel coating includes martensitic, ferritic, and austenitic phases; Due to the same chemical composition of the substrate and the cladding, the weight percentage of elements such as iron, nickel, chromium, and copper did not change from the cladding to the interface. It indicates the uniformity of the chemical composition of the cladding and the substrate. The calculated microhardness for the cladding of stellite6, the substrate and the cladding of stainless steel 7-4PH is about 480, 350, and 350 respectively. The reason for the higher microhardness of the cladding is the presence of chromium carbides (Cr7C3 and Cr23C6) formed in the cobalt field and the cobalt solid solution field of the cladding.
