Ivica Kladarić

The Influence of Multiple-Solution Annealing on Kinetics of Structural Transformation of Maraging Steels

The paper presents effects of multiple solution annealing on kinetics of structural transformation of maraging steels 18 9 5. Multiple solution annealing testing was carried out in dilatometer by simultaneous registration of transformation temperatures austenite start As at heating and martensite start Ms at cooling and registration of linearly dilatatic changes. Analysis of dilatometric curves has quantified coefficients of dilatation during heating and coefficient of contraction during cooling, and has established mathematical model for determination of quantity of retained austenite in microstructure of maraging steels.

Mechanical Properties of Boronizing Steels as Repercussion of Boron Phases

Results of the boride surface layers investigation, obtained by torsion and bending, show better ductility of the monophase Fe2B boride layers than the binary-phase FeB + Fe2B boride layers. This is especially outstanding for samples that are under higher thermal and mechanical load, where the binary-phase layer because of higher local stresses probably has tendency to fall away, respectively to husk.

The Effect of Aging Parameters on Properties of Maraging Steel

In this article, an investigation of aging parameter (temperature and time) effects on mechanical properties and dimensional changes of Maraging 15 10 5 steel is presented. Aging tests were carried out in a dilatometer accompanied by simultaneous registration of forthcoming alterations of size. The results indicate a significant influence of aging temperature and aging time duration on achieved hardness values, as well as on dimensional changes, which is caused by diffusion of alloyed elements from Ni-martensite matrix during aging. On the basis the tests, optimal aging temperature and aging time duration of Maraging 15 10 5 steel are determined.

Research of boride layers growth kinetics on C15 carbon steel

This study reports on formation of borides on C15 carbon steel. Pack boronising has been carried out in temperature range 870–970°C with durations 4–8 h. Average thickness of boride layers ranges from 69.9 μm to 239.2 μm. The aim of this study is to investigate influence of boronising temperature and duration onto average thickness of boride layer, thickness of the compact part of layer and its toothness as well as the change of volume share of boride phase concerning cross section of the layer. Analysis showed the existence of influence of mentioned factors on observed properties of boride layer. As a result, mathematical models showing their functional correlation have been obtained through application of statistical methods.

Improvement of surface layer properties of some constructional steels induced by applying thermodiffusional duplex treatment

The contribution deals with the preliminary results obtained in investigation concerning application of the duplex treatment to the low–carbon and low–alloyed steel samples (C45E, C15E, 42CrMo4 and 20MnCr5). The duplex treatment included boronising (at 900°C for 4 h in Ekabor 3 powder) and subsequent plasma nitriding processes (at 520°C for 40 minutes, 30 vol% nitrogen and 70 vol.% hydrogen, using PN–Mono 5 unit). In this study, the case and core properties of treated steels have been investigated experimentally by using: optical microscopy and SEM observations, X–ray diffraction analysis and measurements of microhardness profile on the cross–section of the treated steel samples. The results obtained by the above techniques are mutually consistent, and they are in agreement with the findings obtained by other researchers.