The influence of surface topography on selected tribological properties of hardened 100Cr6 steel after turning

Results of surface topography analysis and selected tribological properties of samples of 100Cr6 bearing steel after turning with variable feed are presented. The hardness of samples after heat treatment carried out in a vacuum furnace (including quenching and double tempering) was 60 ±1 HRC. The influence of turning feed on surface topography after machining as well as selected tribological properties were determined. Depending on the surface topography of samples, differences between values of friction coefficients and wear rates were about 25%. Moreover, along with the surface roughness changing, different nature of wear was found.

Optimized fatigue performance of martensitic stainless steel AISI 440C using deep rolling integrated into hardening process

The deep rolling process can be modified by annealing at appropriate temperature and time to optimize the fatigue performance of metallic materials. The hardening process of the martensitic stainless steel AISI 440C composes of quenching and double tempering processes. We suggest to integrate the deep rolling process into the hardening treatment because the heat from the tempering process possibly provides sufficient static strain ageing effects. It was found that the deep rolling process can be integrated fully into the hardening process of the martensitic stainless steel AISI 440C, especially in the middle of the double tempering processes. The heat of the tempering process after the deep rolling process leads to beneficial static strain ageing effects as a consequence of greater fatigue lives. Moreover, the maximum fatigue life was detected in this research, when the optimized annealing had been performed instead of the second tempering process.

Precipitation of Secondary Phases in a Supermartensitic 13Cr6Ni2.5MoTi Steel during Heat Treatment

The balance between strength and toughness of supermartensitic steels can be controlled by heat treatment parameters. Quality heat treatment usually consists of quenching and single or double tempering above the Ac1 temperature. Such a treatment results in stabilization of reverted austenite in the tempered martensite. Tempering can also be accompanied by intensive precipitation processes, especially in high alloyed grades. A detailed TEM characterisation of precipitation processes in a 13Cr6Ni2.5MoTi supermartensitic steel proved that single tempering at temperatures of 600°C and 690°C was accompanied by precipitation of three minor phases: MX (TiX), M23C6 and Laves phase (Fe2Mo type). Precipitation processes were more intensive at 690°C. Volume fractions of MX and M23C6 phases were low. Laves phase precipitation was intensive and particles of this minor phase grew fast. However, thermodynamic calculations using the Thermocalc software suggest that Laves phase is not an equilibrium phase in the steel under consideration.

Estimation of the Heat Stability of Hardened Cr-V Cast Irons

The paper describes the structure, properties and heat stability of white cast irons containing 2.5 – 3.0 %C, 14 and 20 %Cr, 3 %V after the secondary hardness treatment (quenching from 1150 °C and double tempering at 560 °C). It is shown that after the secondary hardness treatment M23C6 carbides appear along with the M7C3 phase. Heat stability of the alloys is estimated according to GOST 19265-73 standard. The effect of the temperature and duration of holding at 520–620 °C on structural changes and softening of secondary hardness treated cast irons is considered in comparison with high-speed steel and cast irons of the same composition quenched for the maximum hardness (from 1050 °C). The processes occurring at higher temperatures and long holdings that are responsible for softening of secondary hardness treated cast irons are studied. It is shown that the alloys under consideration after the secondary hardness treatment achieve the hardness of HRC 60 and more, and are able of pertaining it when heated up to 540 °C for 20 hours. This allows using these alloys as wear-resistant materials in the said temperature range.

The Improvement of Product Quality and Production Capacity of Metal Coin Dies by Tempering Treatment and PVD TiN Coating in IsodurTM Steel

In industry of coins production, dies is proportionally compared with the production of coin. Dies, one of the essential components, is externally influenced by geometry, relief, setting parameter production and others. While, internally dies will be affected by its physical property and surface treatment. Phenomenon of dimension deformation and poor wear resistance on dies surface, are part of leakage factor in coin production. In this research, the mechanical properties of IsodurTM steel is being controlled by heat treatment especially tempering treatment and TiN PVD coating with arc cathodic method, in order to produce coining dies. IsodurTM steel samples are heated until temperature 1080◦C in 30 minutes, then samples are quenched and has a single and double tempered treatment at temperature 550◦C in each. After that, samples are coating with TiN and have variables of PVD process holding time 6 and 12 minutes. The result show that hardness of single temper treatment is 62.9 HRC on temperature 550◦C is constant in IsodurTM steel. While the double tempering treatment will decrease the hardness becoming 61.49 HRC and it will make the microstructure being finer than single tempering treatment. The variables of holding time PVD 6 and 12 minutes do not influence the roughness surface relief of coining dies, but they affect the wear resistance that is showed in average capacity production about 251,552 and 262,403 coin per dies by single tempered treatment, and average capacity production about 355,625 and 359,243 coin per dies by double tempered treatment.

Performance Analysis of Cryogenically Treated HSS Profile Cutter by Experimental and FEA

The main objective of the research was to study the effect of cryogenic treatment and double tempering on the tool life of HSS profile cutter in machining EN47 Spring Steel cutting tool components. TiAlN coated HSS profile cutters were cryogenically treated at-175 °C and double tempered at 200 °C. Milling exercises were carried out using un-treated and treated and double tempered tools on EN-47 spring steel reamer components at different machining conditions. The treated HSS profile cutter showed 40 % greater tool life than that of the un-treated in machining EN-47 spring steel components for making flutes. FEA for temperature profile of the cutting tools of the treated and non-treated was performed. Tool tip temperature for untreated and treated were found to be 22 °C and 20 °C respectively.

Microstructural Evolution during Tempering of 16Cr-5Ni Stainless Steel: Effects on Final Mechanical Properties

In this work, the structural behaviour during tempering of two different heats of 16Cr-5Ni supermartensitic stainless steel has been studied by means of dilatometry, transmission electron microscopy and X-ray diffraction. A thermomechanical simulator (Gleeble 3800) has been also used to characterize the effects on final mechanical properties of different tempering temperatures in the range 600 °C to 700 °C and the influence of sub-zero cooling on industrial double tempering treatments. It has been found that the pre-existence of retained austenite in as-quenched conditions can induce significant differences in the microstructural evolution during tempering and on the final mechanical properties of industrial components, thus inducing problems in controlling final maximum hardness allowable by normative requirements.