Estudo do processo SHTPN em amostras de ferro puro sinterizadas a plasma

Abstract

Powder Metallurgy is a manufacturing process with increasing participation and importance in the world scenario. Its advantages for the industry are mainly minimizing costs, increasing productivity, and/or obtaining characteristics only possible from it. However, components produced by powder metallurgy have low corrosion and low mechanical resistance. Thus, performing surface treatments can tailor a component to a specific application, without modifying a part’s entire volume. The surface treatments’ growing application at several industry sectors boosts the development of this area. The SHTPN (Heat Treatment after Plasma Nitriding) process has been studied for some years and provides satisfactory results for quite a few applications, changing the microstructures and consequently the properties of the materials. However, few studies have been done on the subject of porous sintered plasma materials. Thus, the evaluation of SHTPN effects on sintered materials is fundamental for understanding this process when applied to components having a certain degree of porosity. The study of pure iron sintered by plasma and submitted to the SHTPN treatment process is the initial step of a study opportunity that may be applied to other materials in the future, especially ferrous materials with alloy elements. Thus, the present work aimed to study the influence of porosity on the introduction of nitrogen in sintered samples, using the SHTPN technique. Samples with three different levels of porosity and a sample of conventional IF (Interstitial Free) steel were plasma nitrided and solubilized in a salt bath at two different treatment times. The porosity negatively affected the thickness of the nitrided layer, but favored the diffusion process during the solubilization. The pore size and homogeneity proved to be a very important factor in the process.