Internal Friction Study of the Bake-Hardening Properties on Low Carbon Steel Influenced by the Degree of Pre-Deformation

This paper selected cold-rolled low carbon steel as the object of experimentation to better understand that the annealed sample was baked in different degree of pre-deformation span to measure its baking hardening property. The main results of the experiments are as follows: The sample was set in different pre-deformation. Firstly, the baking temperature was set as 170°C and the time span was 20 minutes. The results released that when the degree of pre-deformation was set between 2% and 5%, the BH value increased with the increasing degree of pre-deformation. Secondly, the degree of pre-deformation was set between 5% and 10%, the BH value decreased with the increasing degree of pre-deformation. Thirdly, when the degree of pre-deformation was set at 5%, the BH value reached the maximum. It is illustrated that the BH value increased along with the rising of SKK peak while decreased with the falling of SKK peak. It indicated that the increase of the BH value was mainly due to the intensification of the Cottrell Atmosphere. As the pre-deformation increased, the sum of hSnoek+hSKK decreased. It is worth noting that while under the same circumstances, the sum of hSnoek+hSKK increased after baking.

Elevated-Temperature Wear Study of HVOF spray Cr3C2–NiCr-Coated Die Steels

Wear and surface damage of tools (die materials) in the hot metal forming industry is a critical problem observed and is producing an adverse effect on the process economy. The problem occurs when tool and workpiece interact at higher temperatures. However, the research related to the wear and friction of dies is still lacking. In the present investigation, tribological (wear and friction) studies were conducted with an aim to explore the potential of Cr3C2–NiCr surface coating. The high-velocity oxy-fuel (HVOF) spray technique was used to formulate the coatings. The microhardness, surface roughness, bond strength, and porosity of the coated specimens were found and analyzed. Subsequently, elevated-temperature wear and friction study of the uncoated and coated specimens were done in the laboratory. The study was conducted at 25 N and 50 N loads. The coated specimens showed an increase in wear resistance at all test parameters. The lowest value of coefficient of friction (COF) and the specific wear-rate for the coated specimens were observed at 400 °C. Wear mechanisms were studied by the scanning electron microscopy (SEM) technique. The wear mechanisms were observed to be adhesive in nature at room temperatures and the combination of abrasive/oxidative/adhesive in nature at higher temperatures for the Cr3C2–NiCr-coated specimens.