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This study investigated residual stress evaluations during gaseous nitriding of 50CrMo4 and 31CrMoV9 steels. The nitriding processes were carried out in the NH _3 /H _2 /N _2 atmosphere at 525 °C for 2 h by controlling the nitriding potential. The development of depth-dependent residual stresses was conducted using a Vickers indentation instrument with an estimated geometric correction. The obtained results correlated with the sublayer removal-assisted XRD sin ^2 ψ method. Diffusion layers between 135 and 200 μm were obtained for all samples upon nitriding. The surface hardness values reached 475 HV for 50CrMo4 and 825 HV for 31CrMoV9 steels. The geometric correction factor α was calculated as 78° for a Vickers indenter to measure residual stresses. The generated compressive residual stresses by nitriding increased with increasing nitriding potential by 71% (from −350 to −600 MPa) and 13% (from −750 to −850 MPa) for 50CrMo4 and 31CrMoV9 steels, respectively. An approximately linear relationship was obtained between the hardness and residual stress profiles of the nitrided samples.

A large amount of packaging used mainly in the food industry is obtained by technologies that involve the use of machines such as those that cut with flexible die. The durability of the flexible die is a very important aspect and in this regard the purpose of the research was to identify technologies for its development. Thus, the research considered the analysis of the durability of the knives made of 50CrMo4 steel considering hard chrome-plating treatment, as well as laser hardening of the knives. For the analysis of the durability of the tools, two technological parameters were considered, namely the moment of the tightening force, which had values in the range of 50 Nm–110 Nm, and the die cutting speed, which was adjusted to values in the range of 50–60 m/min. For the analysis of the durability of the flexible die, the wear of the tools was taken into account, as well as the maximum length of the die cut material.

Ultra-high cycle fatigue of structural materials has been an extensively investigated phenomenon in the last thirty years. Nevertheless, the fact that there is no infinite fatigue life of metallic materials has not been considered in structural design very often. This paper presents the results of 50CrMo4 low alloy steel fatigue tests in the high and the ultra-high cycle region showing a considerable difference in the fatigue strength for N = 107 and N = 109 loading cycles. A comparison of shaft mechanical design for different required fatigue lifetimes is provided showing a necessity of designs changes to achieve safe operation in the ultra-high cycle region, thus leading to a 10 % increase in the weight of the shaft. [ABSTRACT FROM AUTHOR]

A large amount of packaging used mainly in the food industry is obtained by technologies that involve the use of machines such as those that cut with flexible die. The durability of the flexible die is a very important aspect and in this regard the purpose of the research was to identify technologies for its development. Thus, the research considered the analysis of the durability of the knives made of 50CrMo4 steel considering hard chrome-plating treatment, as well as laser hardening of the knives. For the analysis of the durability of the tools, two technological parameters were considered, namely the moment of the tightening force, which had values in the range of 50 Nm–110 Nm, and the die cutting speed, which was adjusted to values in the range of 50–60 m/min. For the analysis of the durability of the flexible die, the wear of the tools was taken into account, as well as the maximum length of the die cut material. [ABSTRACT FROM AUTHOR]