Stability of pulsed-magnetic-treated cutting plates in heavy machinery production

The paper presents the results of operational and laboratory tests of cutting inserts made of hard alloys modified by pulsed magnetic field treatment (PMFT) and combined technologies, conducted in the production conditions of enterprises in Kramatorsk on heavy lathes of models KZh16274F3, 1A670F3 and similar. The research was carried out during the processing of structural steels (40Kh) ≈ AISI 5140 (40Cr), (55Kh) ≈ AISI 1055 (55Cr3), (50KhN) ≈ 36CrNi, (45KhNM) ≈ 40CrNiMo, (90KhF) ≈ 100Cr6 (bearing steel), (3Kh13) ≈ AISI 420 (X20Cr13, martensitic stainless) and involved determining the destructive feed, stability and performance of the plates in a range of cutting modes corresponding to the conditions of heavy rough machining. To assess strength, the three-point bending method was used on samples cut from VK3 (WC–3%Co, ISO K10 analogue), VK8 (WC–8%Co, ISO K20 analogue) brazed plates, followed by fractographic analysis. The experiments showed that after PMFT treatment, the mechanical characteristics of the alloys stabilised, the coefficient of variation of tool stability decreased, and the average and γ-percentage periods of operation without failure increased. In particular, the average tool life increased by 1.6 times, the γ-percentage (γ = 80%) increased by 3.5 times, and the coefficient of variation decreased by more than half. Fractographic studies have shown that plate failure occurs mainly due to the formation of main cracks, which originate in areas of micro- and macro-level defect concentration. For samples with a high level of defectiveness, rapid crack growth was observed, which led to premature destruction (the flexural strength was approximately 900 MPa). In contrast, plates with low defect levels showed the development of several parallel cracks, which slowed down destruction and allowed for a higher level of strength (the flexural strength was approximately 1477 MPa). PMFT contributed to a reduction in the spread of the strength limit and slowed down the development of critical cracks. Thus, the developed methodological approaches to assessing the structural strength of cutting plates and the test results confirm the feasibility of using PMFT to improve the efficiency of carbide tools on heavy machine tools. This reduces the likelihood of catastrophic failures, controls crack formation, and increases the service life of tooling in the production conditions of heavy machinery manufacturing enterprises.