"Surface contamination during the heat treatment process can greatly affect the quality of the heat treated parts. Although cleaning the post-heat treated parts is considered a value added process in heat treatment, cleaning parts prior to heat treatment is also important and can influence the outcome of subsequent processes. A series of experiments has been designed to determine the effects of the surface contaminants on nitriding. Nitralloy-135 steel was selected to evaluate the cleaning methods and the effects on the result of subsequent nitriding process. The samples were contaminated with a variety of contaminants, including rust preventive oil, cutting fluid and rust. The contaminated samples were cleaned using either acid or alkaline cleaner. Both cleaned and contaminated samples were nitride in the furnace. To determine the effect of contaminants on gas nitriding, weight gain and the surface hardness were measured. Nitrogen flux was also calculated. The results show that the acid cleaning effectively removes the rust layer. Rusted parts had lower nitrogen absorption than that of the cleaned samples. The parts contaminated by the oil did not reveal any effect on the nitrogen uptake. The surface hardness (Rc) did not show a significant difference between the heavily rusted sample and the clean sample. It has been observed that the nitrogen flux is smaller due to the rust layer on the heavily rusted samples."
Worcester Polytechnic Institute
Materials Science & Engineering
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Liu, Wendi, "The Effects of Contaminants on the Gas Nitriding of Nitralloy-135" (2008). Masters Theses (All Theses, All Years). 1093.
nitriding, contamiants, Surface hardening, Metals, Heat treatment, Nitriding