PSI - Issue 53

Daniel R. Galán-Rivera et al. / Procedia Structural Integrity 53 (2024) 407–415 Daniel R. Galán-Rivera et al. / Structural Integrity Procedia 00 (2019) 000 – 000

414 8

Hardsurfacing with this type of alloy contributes to harden considerably during wear or even during machining, and the use of correct machining tools and techniques is important to achieve optimal results. Furthermore, this powder has excellent resistance to thermal and mechanical. The fifth material subject to study, mainly differ from other in that it does not contain Tungsten Carbides (WC) in its composition. That fact lowers the hardness values of material, minimizing the brittleness of surface coating. In the bases of the experience gained with the previous repairing processes carried out on other materials, the possibility of using a low powder flow was taken into consideration to avoid the appearance of silicates. In a similar way, a preheat treatment between 100 and 120 ° C was applied during tramway rail repairing, ensuring controlled cooling rates between layers. At the end of second layer of repairing, presence of several small cracks forming nearly at an angle of 45 degrees from the repairing direction was observed, maybe due to superficial stress (Fig. 8). After nondestructive tests (penetrant liquids), cracks were clearly identified. We are grinding lightly the surface to ensure the total removal these diagonal cracks. After that, performed the repairing without any new reverse. However, macrographic examination revealed presence of cracks in the injected material, most of them are perpendicular to the fusion line. These cracks may be due to differences in hardness values between the base material and the coating material (Table 2).

Fig. 8. Macrograph and detail of the tram rail repaired with “Material 5 ”

Table 2. Hardness in depth in each process in the coating area and in the heat affected zone, HV10

Hardness in depth (mm) in the powder, HV10

Hardness in depth (mm) in the heat affected zone, HV10

Powder

1

2

3

4

5

6

7

0.12 0.24 0.36 0.48 0.60

0.72

365

390

420

370

399

-

Material 1

264

284

315

317

314

312

-

480

459

424

467

491

-

Material 2

204

225

242

238

-

-

-

330

355

394

390

394

317

Material 3

557

548

361

339

410

476

-

427

470

401

405

425

-

Material 4

516

515

503

528

549

524

548

414

411

436

389

404

454

Material 5

340

387

396

387

327

-

-