EP0126323A2 - Mechanisches Element für die Brennkammer einer Dieselbrennkraftmaschine mit Gleitflächen die Verschleissschutzschichten aufweisen und Verfahren zur Herstellung dieser Schichten - Google Patents

Mechanisches Element für die Brennkammer einer Dieselbrennkraftmaschine mit Gleitflächen die Verschleissschutzschichten aufweisen und Verfahren zur Herstellung dieser Schichten Download PDF

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Publication number
EP0126323A2
EP0126323A2 EP84104633A EP84104633A EP0126323A2 EP 0126323 A2 EP0126323 A2 EP 0126323A2 EP 84104633 A EP84104633 A EP 84104633A EP 84104633 A EP84104633 A EP 84104633A EP 0126323 A2 EP0126323 A2 EP 0126323A2
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EP
European Patent Office
Prior art keywords
wear
layer
fact
running
layers
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP84104633A
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English (en)
French (fr)
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EP0126323A3 (de
Inventor
Paolo Filomeni
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Marelli Europe SpA
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Gilardini SpA
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Publication date
Application filed by Gilardini SpA filed Critical Gilardini SpA
Publication of EP0126323A2 publication Critical patent/EP0126323A2/de
Publication of EP0126323A3 publication Critical patent/EP0126323A3/de
Withdrawn legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B79/00—Running-in of internal-combustion engines
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B77/00—Component parts, details or accessories, not otherwise provided for
    • F02B77/02—Surface coverings of combustion-gas-swept parts
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B3/00—Engines characterised by air compression and subsequent fuel addition
    • F02B3/06—Engines characterised by air compression and subsequent fuel addition with compression ignition

Definitions

  • the present invention relates to a mechanical element, in particular to a component for a combustion chamber of a high speed diesel engine, of the type having sliding surfaces provided with wear-protection layers which are used up during the running-in period, and to a process for obtaining such layers.
  • the object of the present invention is to provide mechanical elements having sliding surfaces coated with wear-protection layers of high thermal stability, of high resistance to oxidation and corrosion, even in the presence of gas containing sulphur, and having low friction and long life.
  • the said object is achieved by the present invention in that it relates to a mechanical element forming a component of a combustion chamber of a diesel engine in particular, of the type comprising at least one sliding surface coated with a wear-protection layer which can be worn away during a running-in period, characterised by the fact that the said wear layer is constituted by a nitride based heat diffusion layer containing a percentage by weight of nitrogen lying between about 4% and 12%.
  • the present invention further relates to a process for forming a wear-protection layer over a sliding surface of an element forming a component of a combustion chamber of a diesel engine, which can be worn away during the running-in period of the said engine, characterised by the fact that it comprises a phase of gaseous nitriding of the said surface performed with ammonia or nitrogen ionised at a temperature less than or equal to 600°C in conditions such as to obtain on the said surface the formation of a layer of nitrides substantially of 6 - type.
  • the element 1 can be constituted by any member forming a component of an engine and in particular by a member forming a component of or involved in the combustion chamber of a diesel engine, such as a piston ring, cylinder sleeve, valve stem or valve seat, a hollow piston for housing the piston rings (both pistons made of spheroidal or laminar cast iron, and those of steel), a gudgeon pin or an element of an injector or an injection pump.
  • the present invention can find application, equally, in one or all of the mechanical members listed above, and in particular to the piston rings which are among the mechanical elements most subjected to wear in an engine, and which have, as is known, three sliding surfaces 2 particularly subjected to wear, and constituted by the outer lateral surfaces thereof intended to cooperate by sliding against the wall of the cylinder sleeve to exercise a sealing action against the combustion gases on one side and the lubricating oil on the other, and by the upper and lower surfaces intended to engage against the walls of the hollow piston in which the piston ring is housed.
  • the said lateral surface 2 of the piston ring is preferably coated, as is illustrated in Figure 1, by a plasma sprayed layer 3 of a metal alloy and/or metal/ ceramic (for example based on Cr-carbide or Mo-carbide, Cr and Nicr) of great hardness substantially greater than that of the material constituting the element 1; in this case the surface 2 does not work directly but serves solely as a support for the layer 3 an outer surface 2a of which constitutes the actual sliding surface of the element 1.
  • a plasma sprayed layer 3 of a metal alloy and/or metal/ ceramic for example based on Cr-carbide or Mo-carbide, Cr and Nicr
  • the sliding surface 2 or 2a is coated with a wear-protection-layer 4 which can be worn away during a running-in period of the element 1, in such a way as to expose the surface 2 (or 2a) of great hardness at the end of the running in period.
  • the layer 4 must have low friction and be relatively soft, of hardness substantially equal to or only slightly greater than that of the material from which the element 1 is made, and must at the same time have a hardness and a resistance to wear such as to allow it to last for a period at least equal to the running-in period of the element 1, which in the case of piston rings or other elements forming components of an engine, is of the order of 1000 hours of operation.
  • wear layers 4 constituted ty nitride based heat diffusion layers containing a percentage by weight of nitrogen lying between about 4% and about 12%, preferably being iron, chrome and molibdenum elements which give, with the nitrogen, nitrides having a quite satisfactory degree of heat stability, and with the element 1 being made of an alloy containing such elements (steel or cast iron), the layer 4 is based on nitrides of iron (and/or chrome or molibdenum) of the chemical formula Fe x N where x is a number, even a decimal, the value of which must lie between two and four, and in particular, must be greater than or equal to two and less than four.
  • Such chemical compounds are well known in the art under the name "white sheet” by which are meant solid E and ⁇ type solutions of nitrogen in iron having compact hexagonal and rhombic structures respectively, and with nitrogen contents lying between 4% and 12%.
  • the ⁇ phase corresponds with a good approximation to the formula Fe 2 N and, at a lower egree of nitriding, to the formula Fe 3 N,
  • ⁇ nitrides or "white sheet” are obtained as unwanted by-products of both liquid and gaseous conventional hard nitriding of mechanical elements, the object of which is to harden the surface thereof by the formation of an intermetallic ⁇ compound of the formula Fe 4 N.
  • ⁇ nitrides The principal known utilisation of ⁇ nitrides has until now consisted in the preparation of layers of such nitrides by means of nitriding operations conducted at high temperatures (close to about 700°C)against the 590°C or a normal nitriding) on surfaces of elements subjected to corrosion by moisture, for the purpose of forming protective e nitride layers which protect the elements against corrosion; in fact it was discovered that ⁇ nitrides in saline solutions had cathodic potentials (about +0.10v NHE) which made them substantially impervious to attack by corrosive agents (protective nitriding).
  • E nitrides or "white sheet” particularly those of iron have low coefficients of friction, high resistance to oxidation and high thermal stability, and an excellent resistance to wear in the particular chemical and physical conditions present in the combustion chamber of a heat engine, in particular both high speed and slow diesel engines, even in the presence of low quality fuels which generate sulphurous combustion gases rich in fuel ash.
  • the said diagrams are each sub-divided into three sections, respectively a,b and c, relating, in order, to the running in period, to the main lifetime period of operation of the element, and to the end period in which collapse by wear takes place; the values of ⁇ are plotted on a logarithmic scale.
  • a substantially parabolic variation of W can be seen, which is free from discontinuities; at the end of the section a (about 1000 hours of operation) the variation of W is such as to join without discontinuity with the rectilinear section b. This corresponds to a lifetime of the layer 4 substantially equal to the running-in period of the element 1.
  • the section a has a discontinuity and is composed of a first curved section with strong inclination, corresponding to a period ⁇ of several tens of hours, and by a rectilinear section which constitutes an extension of the section b; this corresponds to a duration of the electro-deposited protection layer of several tens of hours only, compared with the running-in period of a thousand hours which involves, as can be seen by comparison of the two diagrams, a shorter overall lifetime of the element (the reduction of the lifetime is equal to the quantity ⁇ ), and a greater wear in the running-in period.
  • the same comparative tests have moreover permitted a significant reduction to be detected in the value of the coefficient of friction of the wear-protective layer according to the invention with respect to that of conventional electro-deposited layers.
  • the layer 4 of nitrides is obtained, according to the invention, by means of a particular gaseous nitriding treatment at low temperature (less than or equal to 500°C) performed in nitriding ovens in the form of-autoclaves, in which the nitriding is performed by means of a gaseous fluid of ammonia (NH 3 ) or ammonia mixed with methane (CH 4 ) at an aboslute pressure lying between one and ten Torr (one Torr is approximately equal to 1 mm of mercury 0.0013 atmospheres).
  • NH 3 ammonia
  • CH 4 ammonia mixed with methane
  • the elements to be nitrided are maintained at cathodic potential, whilst the metal walls of the oven are maintained at an anodic potential; between the walls and the elements there is then applied a potential difference sufficient to ionise the gaseous atmosphere between the anode and cathode.
  • the potential difference for performing the nitriding at the temperature indicated (less than or equal to 500 C) must be equal to or greater than 350v.
  • the layer 5 comprises three successive layers, increasingly rich in nitrogen the further they are from the surface 2 (towards the outside) and in fact comprises the outermost layer 4 constituted by E nitrides, followed by an immediately underlying layer 6 of monophasic ⁇ ' nitride having a formula Fe 4 N, followed in turn by a diffusion layer 7 having a low nitrogen content (nitrogen-ferrite and nitrogen- austenite) similar to that which can be found on mechanical pieces subjected to the known TENIFER liquid nitriding process.
  • the layers 6 and 7 are obtained as an involuntary and inevitable consequence of producing the layer 4 and also involve the possible coating layer 3; it has been found that such supplementary layers 6 and 7 underlying the wear layer 4 and covering the surface 2, further improve both the mechanical characteristics and the resistance to wear of the element 1; in fact the layer 7 increases the resilience and the resistance to fatigue of the element 1 with an action similar to that of the diffusion layers which can be obtained with the TENIFER process, whilst the layer of rt nitrides of thickness lying between two and fifteen micron and of much greater hardness than that of the base material of the element 1 , protects the surface 2 from fretting corrosion after the wear layer 4 has been used up at the end of the running-in period, allowing possible coating layers of electro-deposited chrome to be dispensed with.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Pistons, Piston Rings, And Cylinders (AREA)
  • Combustion Methods Of Internal-Combustion Engines (AREA)
  • Shafts, Cranks, Connecting Bars, And Related Bearings (AREA)
EP84104633A 1983-05-16 1984-04-25 Mechanisches Element für die Brennkammer einer Dieselbrennkraftmaschine mit Gleitflächen die Verschleissschutzschichten aufweisen und Verfahren zur Herstellung dieser Schichten Withdrawn EP0126323A3 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IT6754083 1983-05-16
IT67540/83A IT1159435B (it) 1983-05-16 1983-05-16 Elemento meccanico per la camera di combustione di un motore diesel del tipo con superfici di scorrimento provviste di strati protettivi di usura per il periodo di rodaggio e procedimento per ottenere tali strati

Publications (2)

Publication Number Publication Date
EP0126323A2 true EP0126323A2 (de) 1984-11-28
EP0126323A3 EP0126323A3 (de) 1985-12-18

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EP84104633A Withdrawn EP0126323A3 (de) 1983-05-16 1984-04-25 Mechanisches Element für die Brennkammer einer Dieselbrennkraftmaschine mit Gleitflächen die Verschleissschutzschichten aufweisen und Verfahren zur Herstellung dieser Schichten

Country Status (2)

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EP (1) EP0126323A3 (de)
IT (1) IT1159435B (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998019084A1 (en) * 1996-10-28 1998-05-07 Man B & W Diesel A/S Piston rings and/or a piston in an internal combustion engine of the diesel type and a method of running-in of a diesel engine
EP3159427A1 (de) * 2015-10-08 2017-04-26 Mahle International GmbH Ventil für verbrennungsmotoren
WO2021180315A1 (en) 2020-03-11 2021-09-16 Wärtsilä Finland Oy Method of configuring a gas exchange valve assembly in an internal combustion piston engine and a gas exchange valve

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1000288A (en) * 1963-03-25 1965-08-04 Goetzewerke Sealing member
US4074671A (en) * 1974-10-31 1978-02-21 Pennila Simo A O Thin and low specific heat ceramic coating and method for increasing operating efficiency of internal combustion engines
FR2518209A1 (fr) * 1981-12-16 1983-06-17 Ae Plc Bague metallique pour segment et joint d'etancheite et son procede de fabrication

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1000288A (en) * 1963-03-25 1965-08-04 Goetzewerke Sealing member
US4074671A (en) * 1974-10-31 1978-02-21 Pennila Simo A O Thin and low specific heat ceramic coating and method for increasing operating efficiency of internal combustion engines
FR2518209A1 (fr) * 1981-12-16 1983-06-17 Ae Plc Bague metallique pour segment et joint d'etancheite et son procede de fabrication

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
HTM, vol. 29, no. 1, March 1974, pages 42-49, Stuttgart, DE; J. W]NNING: "Neues Verfahren und Anlagen zum Nitrieren mit E-Verbindungsschicht" *
MTZ, vol. 18, no. 9, September 1957, pages 280-283, Stuttgart, DE; Dr. Ing. H.H. BERG: "Echte Einlaufschichten" *
ZEITSCHRIFT F]R METALLKUNDE, vol. 73, no. 6, June 1982, pages 349-353, Stuttgart, DE; K.-T. RIE et al.: "Plasmanitrieren von Eisenwerkstoffen in kohlenstoffhaltigen Gasgemischen" *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998019084A1 (en) * 1996-10-28 1998-05-07 Man B & W Diesel A/S Piston rings and/or a piston in an internal combustion engine of the diesel type and a method of running-in of a diesel engine
EP3159427A1 (de) * 2015-10-08 2017-04-26 Mahle International GmbH Ventil für verbrennungsmotoren
WO2021180315A1 (en) 2020-03-11 2021-09-16 Wärtsilä Finland Oy Method of configuring a gas exchange valve assembly in an internal combustion piston engine and a gas exchange valve
CN115244280A (zh) * 2020-03-11 2022-10-25 瓦锡兰芬兰有限公司 配置内燃活塞发动机中的气体交换阀组件的方法和气体交换阀

Also Published As

Publication number Publication date
EP0126323A3 (de) 1985-12-18
IT8367540A0 (it) 1983-05-16
IT1159435B (it) 1987-02-25

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Inventor name: FILOMENI, PAOLO