On the Use of Repeated Low-Temperature Nitrocementation for Effective Hardening of the Crankshafts of KAMAZ Vehicles, Ground to Repair Dimensions

Purpose of research the aim of the work is to develop an effective technology for surface hardening of the crankshafts of KAMAZ 740 engines, restored by re-grinding to repair dimensions, by means of their accelerated low-temperature nitrocementation in the conditions of car service (car repair) enterprises.
Methods. Nitrocementation of the samples was carried out in a nitrogen-carbon paste. The samples with a nitrocementating coating were heated in a laboratory furnace with a vertical load of SSHOL-12-M3-U4. The nitrocemented samples were subjected to metallographic analysis using an Axio Observer.A1m optical microscope and a Quanta TM 3D200i electron scanning microscope. Phase analysis of diffusion layers on samples nitrocemented according to various modes was carried out on an XRD-7000S X-ray diffractometer. The microhardness of the nitrocemented samples was measured using a Duramin-5 microhardness meter with a computer and software. The hardness of the nitrocemented samples was measured on a TK-2M (Rockwell) hardness tester on the "A" scale according to the standard method.
Results. The technology of low-temperature nitrocementation of nitrided crankshafts of KAMAZ vehicles after their repair by grinding with the removal of the hardened layer from the surfaces of the root and connecting rod necks is presented. It is shown that nitrocementation of 42HMFA steel, from which crankshafts are made, at a temperature of 520...580 °C for 3 hours in a highly active paste ensures the production of hardened layers in depth, structure, phase composition and hardness are almost identical to nitrided layers. Such nitrocementation can be a full-fledged and effective replacement for the re-nitriding of the restored shafts provided for in the technical documentation for the repair of KAMAZ engines, categories E-2, E-3 and E-4.
Conclusion. The low labor intensity and technological simplicity of nitrocementation will allow it to be used to strengthen the crankshafts of all seven repair sizes provided for these parts, which can give a very large economic effect.

1. Likhanov V. A. Dvigateli KAMAZ [KAMAZ engines]. Kirov, Vyatka St. Agricultural Acad. Publ., 2018. 190 p.

2. Denisov A. S. Osnovy formirovaniya ekspluatatsionno-remontnogo tsikla avtomobilya [Fundamentals of the formation of the operational and repair cycle of the car]. Saratov, Saratov St. Univ. Publ., 1999. 352 p.

3. Buravtsev S. K. O sostoyanii kharakteristik kolenchatykh valov i ikh vliyanii na pokazateli dvigatelei [On the state of characteristics of crankshafts and their influence on engine performance]. Dvigatelestroenie = Engine building, 2006, no. 1(223), pp. 38–42.

4. Avtomobili KAMAZ 6kh4: tekhnicheskoe obsluzhivanie i remont [KAMAZ 6x4 cars: maintenance and repair]; ed. by V. N. Barun. Moscow, Izd-vo MO SSSR, 1983. 127 p.

5. Rukovodstvo po ekspluatatsii i tekhnicheskomu obsluzhivaniyu dvigatelei ekologicheskogo klassa Evro-3,4 740.60–3902010RE [Operation and maintenance manual for Euro-3,4 environmental class engines 740.60–3902010RE]. Naberezhnye Chelny, JSC KAMAZ, 2011.

6. Rukovodstvo po ekspluatatsii, tekhnicheskomu obsluzhivaniyu i remontu. Dvigateli KAMAZ 740.11-240, 740.13-260, 740.14-300, 740.30-260, 740.50-360, 740.51-320, 740.50390.1001 KD. ekologicheskogo klassa Evro-3,4 740.60–3902010RE [Operation, maintenance and repair manual. KAMAZ engines 740.11-240, 740.13-260, 740.14-300, 740.30-260, 740.50-360, 740.51-320, 740.50-390.1001 CD. ecological class Euro-3,4 740.60–3902010RE]. Naberezhnye Chelny, JSC KAMAZ, 2002.

7. Issledovanie remontoprigodnosti kolenchatykh valov dvigatelei KAMAZ. Tekhnicheskii otchet [Investigation of maintainability of crankshafts of KAMAZ engines. Technical report]. Naberezhnye Chelny, JSC KAMAZ STC, 2004.

8. Petrosov V. V. Remont avtomobilei i dvigatelei [Repair of cars and engines]. Moscow, Academy Publ., 2007. 222 p.

9. Azamatov R. A., Dazhin V. G., Kulakov A. T., Modin A. I. Vosstanovlenie detalei avtomobilei KAMAZ [Restoration of parts of KAMAZ cars]; ed. by V. G. Dazhin. Naberezhnye Chelny, JSC KAMAZ, 1994. 215 p.

10. Ageeva E. V., Ageev E. V. Povyshenie kachestva remonta i vosstanovlenie detalei sovremennykh transportnykh sistem [Improving the quality of repair and restoration of parts of modern transport systems]. Izvestiya Tul'skogo gosudarstvennogo universiteta. Seriya: Tekhnicheskie nauki = Proceedings of Tula State University. Series: Technical Sciences, 2011, is. 3, no. 3, pp. 503–509.

11. Kuznetsov Yu. A., Kravchenko I. N., Sevryukov A. A., Glinsky M. A. Tekhnologicheskie metody povysheniya dolgovechnosti detalei mashin [Technological methods of increasing the durability of machine parts]. Tekhnologii metallov = Technologies of metals, 2019, no. 5, pp. 34–40.

12. Katalog detalei i sborochnykh edinits KAMAZ-65111 s dvigatelyami urovnya Evro-1, Evro-2, Evro-3 65111-3902001 KD [Catalog of parts and assembly units of KAMAZ-65111 with Euro-1, Euro-2 engines, Euro-3 65111-3902001 CD]. Naberezhnye Chelny, JSC KAMAZ, 2010.

13. Chernoivanov V. I., Lyalyakin V. P., Litovchenko N. N. Resursosberegayushchie vosstanovitel'no-uprochnyayushchie tekhnologii – osnova vtorichnogo proizvodstva detalei [Resourcesaving restorative and strengthening technologies – the basis of secondary production of machine parts]. Vestnik Orlovskogo gosudarstvennogo agrarnogo universiteta. Remont i organizatsiya tekhnicheskogo servisa = Bulletin of the Orel State Agrarian University. Repair and Organization of Technical Service, 2009, no. 1, pp. 2–5.

14. Bondarev S. A. Sovershenstvovanie tekhnologii vosstanovleniya kolenchatykh valov [Improving the technology of restoring crankshafts]. Sovremennye materialy, tekhnika i tekhnologii = Modern materials, equipment and technologies, 2016, no. 2(5), pp. 47–51.

15. Tugushev B. F. [The world practice of restoring crankshafts]. Vosstanovlenie i uprochnenie detalei mashin. Mezhvuzovskii nauchnyi sbornik [Restoration and strengthening of machine parts. Interuniversity scientific collection]. Saratov, Saratov St. Techn. Univ. Publ., 2001, pp. 69–85.

16. Kolmykov V. I., Pereverzev V. M., Barabash A. A., Savelyev S. N. Karbonitrirovanie uluchshaemykh stalei v pastakh [Carbonitriding of improved steels in pastes]. Kursk, Kursk St. Agrarian Acad. Publ., 2000, pp. 67–72.

17. Barabash A. A., Dolzhenkov V. N., Kolmykov V. I., Pereverzev V. M., Pivovar V. P. Nizkotemperaturnoe tsianirovanie konstruktsionnykh uluchshaemykh stalei v tverdoi srede [Lowtemperature cyanidation of structural improved steels in a solid medium]. Kursk, Kursk St. Agrarian Acad. Publ., 2000, pp. 67–72.

18. Kolmykov V. I., Tutov N. D., Nikulin A. A., eds. [Development and research of a highly active saturated medium for nitrocementation of steels at low and high temperatures]. Materialy i uprochnyayushchie tekhnologii – 2008. Sbornik materialov XV Rossiiskoi nauchno-tekhnicheskoi konferentsii s mezhdunarodnym uchastiem [Materials and hardening technologies – 2008. Collection of materials of the XV Russian Scientific and technical conference with international participation]; ed. by V. N. Gadalov. Kursk, Kursk St. Technical Univ. Publ., 2008, pp. 139–144. (In Russ.)

19. Prokoshkin D. A. Khimiko-termicheskaya obrabotka metallov – karbonitratsiya [Chemical and thermal treatment of metals – carbonitration]. Moscow, Metallurgy Publ., 1984. 240 p.

20. Przhenosil B. Nitrotsementatsiya [Nitrocementation]. Moscow, Metallurgy Publ., 1969. 212 p.

21. Kolmykov V. I., Emelyanov S. G., Garaibe N. S. [On the operational properties of materials with heterophase structures]. Materialy i uprochnyayushchie tekhnologii 2009. Sbornik materialov XVII Rossiiskoi nauchno-tekhnicheskoi konferentsii s mezhdunarodnym uchastiem – 2010 [Materials and hardening technologies – 2010. Collection of materials of the XVI Russian scientific and technical conference with international participation]; ed. by V. N. Gadalov. Kursk, Kursk St. Technical Univ. Publ., 2010, pp. 155–158. (In Russ.)

22. Kolmykov V. I., Ryazantsev E. A., Garaibe N. S., eds. [Diffusion of carbon and nitrogen through the crust of carbonitrides]. Materialy i uprochnyayushchie tekhnologii – 2009. Sbornik materialov XVI Rossiiskoi nauchno-tekhnicheskoi konferentsii s mezhdunarodnym uchastiem [Materials and hardening technologies – 2009. Collection of materials of the XVII russian scientific and technical conference with international participation]; ed. by V. N. Gadalov. Kursk, Kursk St. Technical Univ. Publ., 2009, pp. 4–8. (In Russ.)