Vacuum carbonitriding of small-dimension tools formed from high-speed powder steel in low-energy muffle furnaces

Abstract

Vacuum casehardening (VCH) has come into increasingly widespread use in industry due to a number of advantages." the production of a clean unoxidized component surface, reduction in allowances for finish machining, improvement in ecology, and a reduction in outlays for electric energy, equipment, and accessory nlaterials. A procedure for the vacuunl carbonitriding of tools formed from high-speed powder steels in active soot-fiee liquid carburizers is discussed in this paper.Use of high-speed powder steels for the fabrication of special cutting and shaping tools is economically and technically founded [1][2][3], but requires the fulfillment of a number of technological characteristics and special procedures for the heat treatment, pressing, and casehardening [3][4][5][6].Theoretical and practical positions set forth in [5][6][7][8][9] and data on the vacuum treatment of individual types of tools fabricated from high-speed steels [10][11] were employed in evaluating the possibility of using vacuum heat treatment and vacuum casehardening for thin-edge and small-dimension shaping tools formed from powder steels R6M5-P and R6M5K5-MP.Modernized SShOL-1,6.1/1211 and SShOL-1,8,1,2/12M2 furnaces with "hot" retorts were used to conduct vacuum carbonitriding in atmospheres produced by the pyrolysis of liquid monoethanolamine-and triethanolamine-base carburizers with additives of vat residues from the regeneration of ethyl alcohol and vacuum hardening in the 860-1120°C interval. A rough drawing of a steel 12KH18N10T vacuum retort with a system of vacuum inlets and outlets and a device to weight the feed of liquid carburizer is shown in Fig. 1. The vacuum in the metallic muffle was varied from 0.133 to 425 Pa by varying the consumption of liquid mixtures fed through the needle valve of the weighing device. Cooling at various rates was accomplished by varying the nitrogen or argon delivery to the working space, and by moving the muffle into the air in accordance with the scheme outlines by Hesse [12], as well as by transporting the specimens and tools through the air into oil and slat melts.Specimens for a metallographic, x-ray-structural analysis and bending-and impact-strength testing, as well as smalldimension dies, master punches, and die plates were fabricated from extruded bars, strips, and forgings of powder steels R6M5-P, R6M5F3-MP, ROM6F3-MP, and R6M5K5-MP in accordance with Technical Specification 14-1-2988-80 and Technical Specification 14-1-2804-79. The chemical composition of the blanks is presented in Table I. hwestigated of the microstructure and x-ray-structural analysis of specimens treated in accordance with the different regimes were carried out layer-by-layer by grinding off the 40-50-/2m thick diffusion layer. Fractographic and micro-x-rayspectral analysis of the distribution of elements over the cross section of the specimens after impact-bending tests were carried out on a "Camebax" unit. The regimes employed for the vacuum carbonitriding of the high-speed powder steel in atmospheres produced by the pyr...

Laser treatment of powder high-speed steels with prior vacuum hardening and surface impregnation

“…The vacuum quenching before laser treatment was perfornaed in SGV-2.4/15-12 bell furnaces with placement of the tools on stacks [10] and plates from VK-94-1 alumina ceramics. The vacuum cyanidation was performed in sootless carburizers in modernized SShOL-VNTS furnaces [6]. The regimes of the prior heat treatment are presented in Table 2.…”

Cyaniding steels with the use of triethanolamine

“…The use of triethanolamine without additives as the saturating medium is considered in [1] for high-temperature cyaniding (at 880~ and higher) with reference to the works of S. M. Gugel'. The fabrication of a quite hard surface layer in saturating steels in triethanolamine is described in [4], but here the gas mixture is prepared by adding monoethanolamine and bottoms of the regeneration of ethyl alcohol.The use of high-temperature cyaniding creates additional problems, namely, the oxidation of the heaters and the checkerwork of the furnace, which makes it necessary to replace them quite often, the grain growth in the structure of the steel and the necessity for subsequent normalizing or preliminary quenching, and a considerable technological allowance before the cyaniding in order to eliminate the possible deformation of the parts and to remove the burn-on by subsequent grinding.The aim of the present work consisted in the development of a method for cyaniding steel parts at a diminished temperature with the use of triethanolamine without adding any other gas.We studied sliders from steel 38Kh2MYuA, for gates of the fountain equipment of the petroleum industry and specimens from steels 20, 20Kh, and 18KhG ( had the form of plates with openings. The liquid matter was triethanolamine supplied in accordance with the TU 6-09-2448-91 Specifications.…”