On the Wear Resistance of Some Hardfacing Materials

ON THE WEAR RESISTANCE OF SOME SURFACING MATERIALS

Yu. A. Evtyushkin, V. N. Kashcheev, E. L. Wolf

(Presented by the scientific seminar of the Department of Equipment and Technology of Welding Production)

In the course of operation, every machine loses its service properties as a result of wear of parts, assemblies, and the machine as a whole. Metal losses as a result of abrasive wear amount annually to several hundred thousand tons [6]. Abrasive wear is the principal factor limiting the service life of machines of various purposes—agricultural, construction, road-building, mining, and so on [3]. The restoration of worn parts has the aim of returning these parts to the required dimensions and ensuring their original, or even increased, working capacity. Of all methods for restoring parts, surfacing with hard alloys has become the most widespread.

The most widely used method is surfacing with special surfacing electrodes. GOST 10051-62 provides for twenty-five types of electrodes; of these, for surfacing parts operating under conditions of abrasive wear, only five are recommended: EN-U10G5Kh7S-25; EN-U30Kh28S4N4-50; EN-80Kh4SG-55; EN-U30Kh25RS2G-60; EN-U30Kh23R2S2TG-55. However, it should be borne in mind that at present, in order to increase resistance to abrasive wear, more than forty surfacing materials are effectively used [4].

The purpose of the present study was to investigate the resistance to abrasive destruction of metal surfaced with electrodes EN-60M, T-590, OZI-1, NI-1, OMG-N, by the method of a ring rotating in a stream of abrasive particles, proposed by Prof. V. N. Kashcheev, Doctor of Physico-Mathematical Sciences. For the experiments this method of wear was chosen for the following reasons: in the process of destruction of the surfaced surfaces, glazing is excluded even for the softest metals; the comparative investigation of the abrasive wear resistance of various electrode overlays is simple; the question of investigating surfaced metal by this method has not been covered; and, most importantly, the mechanism of destruction of the metallic surface by this method is characteristic of a large number of machines operating under conditions of abrasive wear, for example agricultural machines, excavators, tractors, all kinds of grinding installations, and so forth.

The essence of the method. Abrasive grain, through a device based on the principle of destroying an abrasive arch in the conical opening of a vibrating needle, enters a vertical tube, where under the action of its own weight it gains speed and then strikes the surface-

of a rotating T-shaped disk enclosed in a housing. The grain rebounding from the ring falls into a collector. The gap between the vertical tube and the rotating disk is set smaller than the average diameter of the grains used.

The principal mechanism of destruction of the surfaced surface by a freely striking particle is cutting-scratching with the separation of typical small chips, produced by the tangential component of the force of impact of the abrasive grain on the rotating disk; the normal component of the force ensures penetration through a certain layer of air. The arrangement of the installation is shown in Fig. 1. Test conditions according to the scheme.

Sample dimensions, in mm:

diameter — 90
width — 20
thickness of the surfaced layer — 3.5
weight, g — up to 200
height of grain fall, mm — 50
disk rotational speed, rpm — 3000
abrasive — black carborundum
abrasive consumption — 1 kg in 15 min
wear index — loss of sample weight, in mg.

Fig. 1. Arrangement of the installation

The study was carried out on five samples surfaced with electrodes T-590; EN-60M; OZI-1; OMG-N and NI-1. The first four grades are standard and are regulated by GOST 9466-60 and GOST 10051-62; the fifth is experimental. Electrodes T-590; EN-60M; OZI-1 provide alloying of the deposited metal through the coating, while OMG-N provides alloying both through the coating and through the electrode wire. The first three electrodes have, as the core, electrode wire Sv-08 or Sv-08A; the principal constituent of the coating in T-590 is ferrochrome, in EN-60M—ferrochrome and carbon, and in OZI-1—ferrotungsten. In the OMG-N electrode the core is made of Sv-06N3A wire, and the principal constituent of the coating is ferrochrome and marble. The manufacturer of the electrodes is the Moscow Electrode Plant [5].

After surfacing, the hardness of the deposited metal, \(HV\) (GOST 2999-45), was tested on a “TP” type hardness tester.

Table 1

After the hardness measurement, the samples were tested according to the above-described procedure. The test results were summarized in Table 2.

Table 2

On the basis of the results of the tables, the graph in Fig. 2 was plotted.

Fig. 2. Dependence of the wear of electrosurfaced deposits by free abrasive grain on hardness

Conclusions

1. The metal surfaced with electrode T-590 has the best wear resistance.

2. As can be seen from the graph, in abrasive wear of electrosurfaced deposits by this method, high hardness cannot be associated with high wear resistance, since wear resistance cannot always be characterized by the determination of hardness.

References

1. V. N. Kashcheev, V. M. Glazkov. Proceedings of conferences on methods of wear testing. USSR Academy of Sciences, Moscow, pp. 24–30, 1962.

2. V. N. Kashcheev. Izv. vuzov. Fizika, issue 1, pp. 193–194, 1968.

3. M. M. Khrushchov, M. A. Babichev. Abrasive Wear. Nauka Publishing House, Moscow, 1970.

4. L. S. Livshits et al. Fundamentals of Alloying of Surfaced Metal. Mashinostroenie, Moscow, 1969.

5. Electrodes for Arc Welding and Surfacing. Catalogue, Naukova Dumka Publishing House, Kiev, 1967.

6. V. N. Tkachev et al. Induction Surfacing of Hard Alloys. Mashinostroenie, Moscow, 1970.