Features of prediction of the rupture-strength characteristics of metallic materials for times-to-rupture greater than 100,000 h

The special features of various bearing deformation measurements for pin-type bearing tests of metallic materials are considered along with their impact on the magnitude of the «bearing elastic modulus» and bearing stress. These bearing test methods are present in ASTM and various institutional standards, though no state standard (GOST, GOST R) is currently available for bearing test method of metallic materials. Analysis of additional deformations which arise in determining the degree of hole bearing deformation is carried out. A set of sources of additional deformations is shown to be characteristic for each test procedure and is attributed to the design features of the device, the site and a way of mounting the extensometer. Additional deformations can be both tensile and compressive. It is shown that the impact of additional deformations on the «bearing elastic modulus» is limited to 14% for different procedures. No difference between the methods is revealed with regard to determination of the strength characteristics. At the same time the dispersion decreases with increase in plastic deformation and for bearing deformation about 4% the variation coefficient for all methods is no more than 1%. Advantages and shortcomings of the bearing test methods which affect the reproducibility of the results are considered. The effect of the specimen geometry on the bearing characteristics is considered. It is shown that increase both in the distance from the edge of the bearing specimen to the center of the hole for 1163T, VT6ch, 30KhGSA alloys and residual bearing deformation up to 6%, increase bearing strength characteristics.

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Innovative Densification Process of a Fe-Cr-C Powder Metallurgy Steel

Metals ◽

10.3390/met11040665 ◽

2021 ◽

Vol 11 (4) ◽

pp. 665

Author(s):

Federico Simone Gobber ◽

Jana Bidulská ◽

Alessandro Fais ◽

Róbert Bidulský ◽

Marco Actis Grande

Keyword(s):

Heat Treatment ◽

Powder Metallurgy ◽

Process Parameters ◽

Rupture Strength ◽

Mechanical Resistance ◽

Metallic Materials ◽

Transverse Rupture Strength ◽

Sinter Forging ◽

Metallurgy Steel ◽

Main Factor

In this study, the efficacy of an innovative ultra-fast sintering technique called electro-sinter-forging (ESF) was evaluated in the densification of Fe-Cr-C steel. Although ESF proved to be effective in densifying several different metallic materials and composites, it has not yet been applied to powder metallurgy Fe-Cr-C steels. Pre-alloyed Astaloy CrM powders have been ad-mixed with either graphite or graphene and then processed by ESF. By properly tuning the process parameters, final densities higher than 99% were obtained. Mechanical properties such as hardness and transverse rupture strength (TRS) were tested on samples produced by employing different process parameters and then submitted to different post-treatments (machining, heat treatment). A final transverse rupture strength up to 1340 ± 147 MPa was achieved after heat treatment, corresponding to a hardness of 852 ± 41 HV. The experimental characterization highlighted that porosity is the main factor affecting the samples’ mechanical resistance, correlating linearly with the transverse rupture strength. Conversely, it is not possible to establish a similar interdependency between hardness and mechanical resistance, since porosity has a higher effect on the final properties.

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Evaluating the reliability of predictions of the rupture strength of metallic materials for long service lives

Strength of Materials ◽

10.1007/bf00773237 ◽

1990 ◽

Vol 22 (2) ◽

pp. 195-201

Author(s):

V. I. Kovpak

Keyword(s):

Rupture Strength ◽

Metallic Materials

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Evaluation of the Properties of an Electro-Sinter-Forged Bearing Steel

10.20944/preprints202009.0364.v1 ◽

2020 ◽

Author(s):

Róbert Bidulský ◽

Federico Simone Gobber ◽

Alessandro Fais ◽

Jana Bidulská ◽

Marco Actis Grande

Keyword(s):

Rupture Strength ◽

Bearing Steel ◽

The Other ◽

Mechanical Resistance ◽

Metallic Materials ◽

Experimental Characterization ◽

Transverse Rupture Strength ◽

Sinter Forging ◽

Bearing Steels ◽

Conventional Press

In this study one of the most innovative sintering techniques up to date was evaluated: Electro-Sinter-Forging (ESF). Despite it has been proved to be effective in densifying several different metallic materials and composites, bearing steels such as 100Cr6 have never been processed so far. Pre-alloyed Astaloy CrM powders have been ad-mixed with either graphite or graphene and then processed by ESF to produce a 100Cr6 equivalent composition. Porosity has been evaluated by optical microscopy and compared to that one of 100Cr6 commercial samples. Mechanical properties such as hardness and transverse rupture strength were tested on samples produced by employing different process parameters and then submitted to different treatments (machining, heat treatment). The experimental characterization highlighted that porosity is the factor mostly affecting mechanical resistance of the samples, correlating linearly to the transverse rupture strength. Hardness on the other side does not correlate to the mechanical resistance because process related cracking has a higher effect on the final properties. Promising results were obtained that give room to the sinterability by ESF of materials difficult to sinter by conventional press and sinter techniques.

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