Abstract
Steels which are utilized in the manufacturing of specific parts of military technology such as crankshafts of engines in heavy-duty vehicles or barrels of guns must be subsequently modified by heat treatment according to the requirements of customers. Despite the hard surface of martensitic structure obtained by hardening process, steels have a low wear resistance and high values of coefficient of friction. To improve these parameters and due to the fact that many of steels which are utilized for manufacturing of mentioned parts are also categorized as Nitralloy steels, in this paper, the improvement in these properties of chosen steels by the application of plasma nitriding has been studied. The steel equivalent 17Ni4CrMo (i.e., CSN 41 6720) and equivalent 42CrMo4 (i.e., CSN 41 5142) were chosen for the study. The chemical composition of chosen steels was verified by optical emission spectrometry. The microstructure and the diffusion layer were observed by optical microscopy due to the evaluation of layer parameters important for the lifetime. ZWICK ZHU 2.5 was used for a measurement of the universal hardness of the surface and values of graphs of microhardness were obtained by the device LM 247AT LECO from a cross-section of samples. The coefficient of friction was determined by Bruker CERT-UMT-3 with a ball-on-disc method. The parameters of wear paths were obtained by Talysurf CLI 1000. After the application of plasma nitriding technology, the hardness of both steels was rapidly increased in comparison with non-nitrided samples. According to the comparison of coefficients of friction with respect to the parameters of the measurement, the coefficient of friction of nitrided samples decreases with increasing temperature, which is essential knowledge for the weapon industry, especially the construction of bore barrel.
Highlights
IntroductionThe contemporary trend in the automotive and weapon industry of constantly improving the performance of special parts of weapons and engines, while decreasing the weight and dimension of weapon and engines’ parts at the same time, has the effect of higher requirements for quality [1]
The contemporary trend in the automotive and weapon industry of constantly improving the performance of special parts of weapons and engines, while decreasing the weight and dimension of weapon and engines’ parts at the same time, has the effect of higher requirements for quality [1].The mechanical parts of systems are innovating due to needs in the “army” area, especially in the sphere of the current trend of development of autonomous systems [2]
Methods including a microstructure assessment, microhardness and universal hardness measurements accompanied by measurements of coefficient of friction under different conditions were utilized
Summary
The contemporary trend in the automotive and weapon industry of constantly improving the performance of special parts of weapons and engines, while decreasing the weight and dimension of weapon and engines’ parts at the same time, has the effect of higher requirements for quality [1]. Nitriding is applicable for treating the outer surfaces of highly exposed parts of military technology as well as for the inner surfaces of barrel bores of small arms, where parameters such as resistance to wear and hardness are essential as well as in the case of cutting tools [12,13]. Due to these facts, in this paper, the improvement in the surface properties of chosen steels by the application of plasma nitriding is studied
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