PSI - Issue 40

N.B. Pugacheva et al. / Procedia Structural Integrity 40 (2022) 372–377 N.B. Pugacheva, T.M. Bykova / Structural Integrity Procedia 00 (2022) 000 – 000

373

2

operational capabilities of machines and aggregates mean new requirements for highly wear-resistant materials with adequate structural strength parameters. A promising direction is the development of new SHS-composites with a plastic matrix based on iron, nickel, cobalt, copper, and aluminum. It is important to establish the role of eutectics, which inevitably appear during the synthesis of multicomponent systems such as Fe-Ni-Ti-C-B Pugacheva et al. (2019). The strength characteristics will largely be determined not only by the strengthening phases (TiC and TiB 2 ), but also by the structure of the matrix. The heterophase nature of the matrix will inevitably lead to inhomogeneity of the distribution of micromechanical properties over the volume of the composite, which will affect the strength and functional properties. In this regard, it is very important to establish the nature of the distribution of micromechanical properties over the cross section of the composite and its influence on the nature of fracture after mechanical tests. 2. Materials and methods Samples of the Fe-Ni-Ti-C-B composite obtained by SHS according to the technique described earlier in the works Nikolin et al. (2017) and Pugacheva et al. (2019) were used as materials for the studies. Structure of the composite was investigated on a scanning electron microscope TESCAN VEGAII XMU. Hardness, according to Rockwell, was measured on a hardness tester HR 5006 on the C scale. Local chemical composition of phases was determined by energy and wave dispersive OXFORD spectroscopy. Phased x-ray diffraction analysis was completed on an X-ray diffractometer SHIMADZU in K α chromium radiation. Instrumental indentation was carried out on a Fischerscope HM2000 XYm measuring system using a Vickers indenter and WIN-HCU software at a maximum load of 0.980 N, a loading time of 20 s, a hold time at a load of 15 s, and an unloading time of 20 s according to the standard ISO 14577 – 2 – 2015. The error in the characteristics of microhardness and microindentation was calculated from 10 measurements with a confidence level of p = 0.95. According to the results of indentation, the following indicators of micromechanical properties were determined: Vickers microhardness ( Н V), contact modulus ( Е *), component of the work of plastic deformation during indentation ( φ ), indentation creep ( С IT ), index of the proportion of elastic deformation in the total deformation during indentation H IT /E (H IT - indentation hardness at maximum load), elastic restoration R e . The indicators φ , С IT , R e were determined using the following formulas: ( )   W /W % t e 100 1  = −  , (1)

h h h max −

,

(2)

1 

100

C

%

=

IT

1

h R h h max e − =

1

,

(3)

1

where W e - the work of elastic deformation during indentation, released when the applied load is removed, W t - total mechanical work during indentation, determined by the area under the load curve, h 1 – indenter penetration depth corresponding to the initial point of the horizontal section on the loading curve, h max – maximum penetration depth of the indenter. Lateral bend trials were conducted using GOST 20019- 74 “Sintered hard alloys. Transverse bending strength trial method”. Trials were conducted on samples Type A (dimensions 35x5x5 mm), trial speed was 0.2 mm/min, and distance between support axis was 30 mm. Transverse bending strength R bm 30 was calculated using the following formula:

2 b h R F l bm     = 3

,

(4)

2