The present work focuses on investigating the wear and friction characteristics of the Atmospheric Plasma Sprayed Cr 3 C 2 -NiCr coatings deposited onto the surface of die steel material. The as-sprayed specimens were characterized. The coating porosity, bond strength and microhardness values were evaluated. Wear tests were performed on the hightemperature pin-on-disc tribometer at room temperatures, 400°C and 800°C under two loads as 25N and 50N in the laboratory. The wear mechanisms of all the worn-out samples were studied by scanning electron microscopy (SEM) technique. The specific wear rates and the coefficient of friction values were analyzed. The developed coating showed better wear resistance than its uncoated counterpart. The coefficient of friction values for coated specimens decreased at elevated temperatures. At room temperatures, the wear mode was observed to be adhesive and further at elevated temperatures of testing, the wear mode was observed to be the combination of oxidative, adhesive and abrasive.

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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.

Wear, plastic deformation, and mechanical fatigue of dies are the most common failures found during hot forming operations at elevated temperatures. The change in frictional behaviour also happens. The performance of the forming operation is affected. To ensure the quality of the end products and productivity, it has become very important to control the wear and friction of die materials. Surface treatment techniques with superior wear properties and good performance can enhance the life and functionality of dies. Plasma nitriding is the most rapidly developing technique for hot forming dies. It is a cost-effective technique and improves the mechanical properties of the die surfaces. This chapter explains the tribology of hot forming dies, the plasma nitriding technique, and the procedures to develop plasma nitriding on the die steels. Thereafter, the tribological behaviour of AISI H11 and AISI H13 plasma nitrided die steels has been reported. Plasma nitriding was found to be most promising and effective in reducing wear and friction at elevated temperatures.

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