RESEARCH OF LOW TEMPERATURE NITROCARBURIZING TECHNOLOGY FOR COMPLEX HARDENING OF MACHINE PARTS

The study of changes in the microstructure, thickness of the ε-phase and the hardness of diffusion coatings obtained by varying the temperature in the process of low-temperature nitrocarburizing was carried out. Studies have shown the possibility, through the use of low-temperature nitrocarburizing technology, to reduce the labor intensity of technological operations, shorten the processing time and reduce energy consumption.

Experimental analysis and modelling of temperature- and humidity-controlled curing

There has been much discussion about modelling the reaction kinetics of a curing polymer. Typically, curing is described by the development of a variable called degree of curing as a function of temperature and time. The material considered in this paper exhibits two different curing mechanisms, namely temperature-activated and diffusion-based. To be able to describe the complex hardening process, the material is extensively analysed experimentally, and a thermodynamically consistent coupled reaction kinetics model is formulated based on experimental observations. This model enables the implementation of the thermal, caloric, and mechanical properties of the material into a finite element (FE) framework.

Surface Modification of Broaches from the Powder High Speed Steels Applied to Processing of Aviation Products from Heat-Resistant Alloys

This paper considers an approach to improve durability of broaching tools made of high alloyed powder metallurgical high-speed steels by complex treatment which includes ion nitriding and following deposition of wear-resistant coating (Nb, Ti,Al)N using two-stage vacuum-arc discharge. Broaching tools complex hardening conditions which provide minimal wear rate when machining heat-resistant nickel alloy Inconel 718 used for turbine discs are defined.

Investigation of the Beginning of Plastic Yielding and the Hardening Behaviour under Biaxial Tension

The main focus of the experimental observation deals with the investigation of the plasticyielding of DC06 and DP600 under biaxial tension in comparison to an identified material modelwith an isotropic hardening behaviour. The isotropic hardening law describes the hardeningbehaviour of the material by application and approximation of the flow curve. Prevalent hardeninglaws are proposed by Swift (1952) or Hockett and Sherby (1975) and lead to an expansion of theyield surface in the stress space. By reasons of good accordance in an earlier survey the givenmaterials are modeled by the yield criterion Yld2000-2d and the isotropic hardening law of Swift.In this case the yield loci at different experimental states of plastification are compared with theyield loci given from the isotropic expansion of the Yld2000-2d yield surface. Furthermore apossible approach for modelling the change of the yield criterion’s shape in the stress space duringplastification is shown. With respect to further investigations additional research work is neededincluding extended and complex hardening laws to describe the real material behaviour sufficiently.