Treatment method for improving wear resistance and corrosion resistance of diesel engine plunger and barrel assembly

Abstract

The invention provides a treatment method for improving wear resistance and corrosion resistance of a plunger and barrel assembly of a diesel engine, which comprises the following steps: heating the plunger and barrel assembly to an austenitizing temperature of 750-790 DEG C, and preserving heat for a certain time to obtain the austenitized plunger and barrel assembly; cooling the austenitized plunger and barrel assembly to 680-720 DEG C along with the furnace, carrying out isothermal treatment for a certain period of time, then cooling the austenitized plunger and barrel assembly to 650 DEG C along with the furnace, taking out the austenitized plunger and barrel assembly, and carrying out air cooling to obtain the isothermal treated plunger and barrel assembly; the plunger and barrel assembly subjected to isothermal treatment is subjected to plasma composite titanizing and carbonizing treatment; and the plunger and barrel assembly subjected to titanizing and carbonizing treatment is sequentially subjected to quenching treatment, ice-cooling treatment and tempering treatment. According to the treatment method for improving the wear resistance and the corrosion resistance of the plunger and barrel assembly of the diesel engine, a TiC high-hardness permeation layer can be obtained on the surface layer of the part, so that the wear resistance and the corrosion resistance of the plunger and barrel assembly are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of alloy metal heat treatment, and in particular relates to a treatment method for improving the wear resistance and corrosion resistance of a diesel engine plunger pair. Background Art

[0002] GCr15 is a commonly used alloy material with excellent mechanical properties, wear resistance and corrosion resistance, and is widely used in the automotive, aerospace and other fields. The use of GCr15 material in the design of high-horsepower diesel engine parts is based on its high hardness, uniform structure, good wear resistance and high contact fatigue characteristics after quenching and tempering. For a long time, the contact fatigue test of the parts, the manufacturing process of the raw materials of the parts, and the experimental research on high-temperature sliding wear and micro-motion wear have been studied in order to improve the performance. First, starting from the material properties of GCr15 bearing steel, the purity of the raw materials themselves is guaranteed. Secondly, starting from the heat treatment process of GCr15 bearing steel, in-depth research is conducted on the control of quenching and tempering temperature, holding time and cooling time to minimize the level of carbides. Simulation analysis is used to study the deformation law and stress condition of the parts to provide test materials for contact fatigue and wear tests. The test parameters are referenced; the contact fatigue performance, fretting wear and sliding wear behavior of bearing steels with different microstructures at different temperatures are studied according to the service conditions, and then the contact fatigue failure mechanism of the pairs is analyzed; after the test, the fatigue failure and wear morphology, fatigue cracks and micromorphology of the sample surface are observed, and the fatigue damage mechanism and wear mechanism of the pairs are analyzed, in order to select the best performance heat treatment process for the pairs under different service conditions; after many tests and analyses, the heat treatment process has been improved and improved many times, which effectively improves the material and the organizational properties after heat treatment, but there are still wear and corrosion problems; therefore, a new treatment method for improving the wear resistance and corrosion resistance of diesel engine GCr15 plunger pairs is developed to improve the mechanical properties and fatigue resistance of the pairs, which has important practical value. Summary of the invention

[0003] In view of this, the present invention aims to propose a treatment method for improving the wear resistance and corrosion resistance of a diesel engine plunger pair, so as to solve the wear and corrosion problems of the plunger pair after the existing heat treatment process.

[0004] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0005] A treatment method for improving the wear resistance and corrosion resistance of a diesel engine plunger pair, comprising:

[0006] The plunger pair is heated to an austenitizing temperature of 750-790°C and kept at this temperature for a certain period of time to obtain an austenitized plunger pair;

[0007] The plunger pair after austenitization treatment is cooled to 680-720°C in the furnace and is isothermally treated for a certain period of time, and then cooled to 650°C in the furnace and then taken out for air cooling to obtain the plunger pair after isotherm treatment;

[0008] The plunger pair after the isothermal treatment is subjected to plasma composite titanium-carbon infiltration treatment to obtain a plunger pair after the titanium-carbon infiltration treatment;

[0009] The plunger pair after the titanium carburizing treatment is sequentially subjected to quenching treatment, ice cooling treatment, and tempering treatment to obtain a processed plunger pair.

[0010] Furthermore, the step of heating the plunger pair to an austenitizing temperature of 750-790° C. and keeping the temperature for a certain period of time includes:

[0011] Heat the plunger assembly to the austenitizing temperature of 750-790°C and keep it at that temperature for no more than 3 hours.

[0012] Furthermore, the plunger pair after austenitization treatment is cooled to 680-720°C in the furnace and is isothermally treated for a certain period of time, and then cooled to 650°C in the furnace and taken out for air cooling to obtain the plunger pair after isotherm treatment, including:

[0013] The plunger pair after austenitizing treatment is cooled to 680-720°C and is isothermally maintained for no more than 4 hours, then cooled to 650°C in the furnace and then taken out for air cooling to obtain the plunger pair after isothermally treated.

[0014] Furthermore, after the plunger pair after austenitizing treatment is cooled to 680-720°C in the furnace and is isothermally treated for a certain period of time, it is then cooled to 650°C in the furnace and then taken out for air cooling to obtain the plunger pair after isothermally treated, the method further includes:

[0015] The end faces of the plunger pair after the isothermal treatment are polished and cleaned.

[0016] Furthermore, the plunger pair after the isothermal treatment is subjected to plasma composite titanium-carbon infiltration treatment to obtain the plunger pair after titanium-carbon infiltration treatment, comprising:

[0017] The plunger pair after isothermal treatment is placed on a DC power supply support of a plasma metallization device and placed inside a cathode;

[0018] Placing the titanium material and the carbon material on the auxiliary cathode structure, and making sure that the titanium material and the carbon material do not contact the plunger couple after the isothermal treatment;

[0019] Inert gas is used as protective gas, and the gas pressure in the plasma metallization equipment is controlled within the range of 30-90Pa, the temperature is controlled at 780°C, the insulation time is 3 hours, the cathode voltage is 600V, the source voltage is 1000V, and the plunger pair after the isothermal treatment is subjected to plasma composite titanium-carbon treatment to obtain the plunger pair after titanium-carbon treatment.

[0020] Furthermore, the inert gas is argon.

[0021] Furthermore, the titanium material is in strip shape.

[0022] Furthermore, the carbon material is a graphite strip.

[0023] Further, in the process of using inert gas as protective gas, controlling the gas pressure in the plasma metallization equipment within the range of 30-90 Pa, controlling the temperature at 780° C., holding time for 3 hours, cathode voltage at 600 V, source voltage at 1000 V, and subjecting the plunger pair after isothermal treatment to plasma composite titanium-carbon treatment to obtain the plunger pair after titanium-carbon treatment, the method comprises:

[0024] The plunger pair after titanium carburizing treatment is furnace cooled to 650° C. and then air cooled.

[0025] Furthermore, the plunger pair after the titanium carburizing treatment is subjected to quenching treatment, ice cooling treatment, and tempering treatment in sequence to obtain a processed plunger pair, including:

[0026] The temperature during quenching is controlled at 840°C;

[0027] The temperature was controlled at -80°C during ice-cooling treatment;

[0028] The temperature during tempering is controlled at 160°C.

[0029] Compared with the prior art, the treatment method for improving the wear resistance and corrosion resistance of the diesel engine plunger pair described in the present invention has the following advantages:

[0030] (1) The treatment method for improving the wear resistance and corrosion resistance of diesel engine plunger parts described in the present invention can significantly improve the corrosion resistance and cavitation corrosion resistance of parts through titanium infiltration, and increase the surface hardness and wear resistance of parts. The reason why titanium infiltration can significantly improve the corrosion resistance and wear resistance is that the infiltration of titanium on the surface of parts at high temperature generates fine and dispersed TiC hard phases, which can achieve the effect of fine grain strengthening and dispersion strengthening by pinning dislocations and hindering the movement of grain boundaries, greatly improving the surface hardness and wear resistance. At the same time, titanium carbide has extremely high chemical stability and extremely high microhardness, which is much higher than the hardness of other metal carbides (for example, tungsten carbide, molybdenum carbide, vanadium carbide, chromium carbide, etc.).

[0031] (2) The treatment method for improving the wear resistance and corrosion resistance of diesel engine plunger parts described in the present invention can significantly improve the corrosion resistance and cavitation corrosion resistance of parts through titanium infiltration, increase the surface hardness and wear resistance of parts, and simultaneously perform carburization because during the ion titanium infiltration process, the strong ion bombardment causes a large number of titanium atoms transported to the sample surface and iron and carbon atoms in the matrix to sputter out. The sputtering loss of titanium atoms can be continuously transported to the sample surface by the titanium target to be replenished, while iron and carbon atoms cannot be replenished from the outside and decrease, especially the carbon atoms with a lower content, the surface concentration decreases more significantly. At the same time, titanium is a strong carbide-forming element, and its affinity with carbon is stronger than that of iron. It can capture carbon atoms from iron, which also causes a decrease in the surface carbon concentration. Therefore, in order to maintain the balance of carbon concentration and due to the decrease in the surface carbon content, carbon infiltration is performed simultaneously to maintain the stability of the matrix carbon content and ensure that a normal structure is obtained during the subsequent heat treatment process. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0033] Figure 1 The present invention is a flowchart of a method for improving the wear resistance and corrosion resistance of a diesel engine plunger pair according to a first embodiment of the present invention.

[0034] Figure 2 The present invention is a schematic structural diagram of a plunger pair after being treated by a treatment method for improving the wear resistance and corrosion resistance of a diesel engine plunger pair. DETAILED DESCRIPTION

[0035] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0036] Embodiment 1

[0037] Figure 1 This is a flow chart of a treatment method for improving the wear resistance and corrosion resistance of a diesel engine plunger pair according to the first embodiment of the present invention. This treatment method can be used to treat plunger pairs used in high-horsepower diesel engines under high-load conditions, and can effectively improve the wear resistance and corrosion resistance of plunger pairs. Figure 1 , this method specifically includes the following steps:

[0038] Step 101, heating the plunger pair to an austenitizing temperature of 750-790°C and keeping the temperature for a certain period of time to obtain an austenitized plunger pair.

[0039] Step 102, the plunger pair after austenitization treatment is furnace-cooled to 680-720°C and isothermally treated for a certain period of time, and then is furnace-cooled to 650°C and taken out for air cooling to obtain the plunger pair after isotherm treatment.

[0040] Step 103, subjecting the plunger pair after the isothermal treatment to a plasma composite titanium-carburizing treatment to obtain a plunger pair after the titanium-carburizing treatment.

[0041] Step 104, subjecting the plunger pair after the titanium carburizing treatment to quenching treatment, ice cooling treatment, and tempering treatment in sequence to obtain a processed plunger pair.

[0042] Preferably, step 101 specifically includes the following steps:

[0043] Heat the plunger assembly to the austenitizing temperature of 750-790°C and keep it at that temperature for no more than 3 hours.

[0044] Since the heating temperature of spheroidizing annealing is a key factor affecting whether the degree of spheroidization is complete or not. The appropriate selection of heating temperature can not only ensure the disappearance of lamellar pearlite, but also retain a part of carbides that are not completely dissolved in austenite as spheroidizing cores, and finally form a normal spheroidized structure of coarse granular carbides. When the austenitizing temperature is very high, the carbides are completely dissolved and homogenized, and lamellar pearlite is always obtained after cooling. Therefore, this embodiment can ensure the spheroidizing annealing treatment effect of the plunger pair by controlling the austenitizing temperature at 750-790°C and keeping it warm for no more than 3 hours.

[0045] Preferably, step 102 specifically includes the following steps:

[0046] The plunger pair after austenitizing treatment is cooled to 680-720°C and is isothermally maintained for no more than 4 hours, then cooled to 650°C in the furnace and then taken out for air cooling to obtain the plunger pair after isothermally treated.

[0047] In actual application, the cooling rate directly affects the size and uniformity of carbide particles. If the cooling is too fast, the carbide particles are too fine, and there is a possibility of forming flaky carbides, which makes the hardness too high. If the cooling is too slow, the carbide particles are too coarse. Therefore, this embodiment can ensure the treatment effect of the plunger pair by controlling the isothermal cooling of the plunger pair.

[0048] Preferably, in step 102, after the plunger pair after austenitizing treatment is cooled to 680-720°C with the furnace and isothermally treated for a certain period of time, it is then cooled to 650°C with the furnace and then taken out for air cooling (i.e., air cooling or room temperature cooling) to obtain the plunger pair after isotherm treatment, the method further includes:

[0049] The end faces of the plunger pair after the isothermal treatment are polished and cleaned.

[0050] Specifically, the bottom surface of the plunger pair after the isothermal treatment can be polished and cleaned with alcohol or acetone to ensure the contact effect between the bottom surface of the plunger pair after the isothermal treatment and the DC power supply bracket, thereby ensuring the conductive performance.

[0051] Preferably, in step 103, the following steps are specifically included:

[0052] Step 1031, placing the plunger pair after the isothermal treatment on a DC power supply support of a plasma metallization device and inside a cathode.

[0053] Step 1032: placing a titanium material and a carbon material on the auxiliary cathode structure, and making sure that the titanium material and the carbon material do not contact the plunger pair after the isothermal treatment.

[0054] Step 1033, using inert gas as protective gas, and controlling the gas pressure in the plasma metallization equipment within the range of 30-90Pa, the temperature is controlled at 780°C, the insulation time is 3 hours, the cathode voltage is 600V, the source voltage is 1000V, and the plunger pair after the isothermal treatment is subjected to plasma composite titanium-carbon treatment to obtain the plunger pair after titanium-carbon treatment.

[0055] In actual application, the inert gas is argon, the titanium material is in strip or short strip shape, and the carbon material is graphite strip. Among them, the plasma metallization equipment in the plasma composite titanium-carbonization treatment can adopt a multifunctional plasma chemical heat treatment equipment with a power of 10-20KW.

[0056] Preferably, in step 1033, the inert gas is used as the protective gas, and the gas pressure in the plasma metallization equipment is controlled within the range of 30-90 Pa, the temperature is controlled at 780° C., the holding time is 3 hours, the cathode voltage is 600 V, the source voltage is 1000 V, and the plunger pair after the isothermal treatment is subjected to plasma composite titanium-carbon infiltration treatment to obtain the plunger pair after titanium-carbon infiltration treatment, and the method includes:

[0057] Step 1034, cooling the plunger pair after titanium carburizing treatment to 650°C in the furnace and then air cooling.

[0058] Preferably, the plunger pair after the titanium carburizing treatment is subjected to quenching treatment, ice cooling treatment, and tempering treatment in sequence to obtain the processed plunger pair, including:

[0059] The temperature during quenching is controlled at 840°C;

[0060] The temperature was controlled at -80°C during ice-cooling treatment;

[0061] The temperature during tempering is controlled at 160°C.

[0062] The present embodiment provides a treatment method for improving the wear resistance and corrosion resistance of a diesel engine plunger pair, wherein the plunger pair is heated to an austenitizing temperature of 750-790°C and kept at this temperature for a certain period of time to obtain an austenitized plunger pair; then the austenitized plunger pair is furnace cooled to 680-720°C and kept isothermal for a certain period of time, then furnace cooled to 650°C and taken out for air cooling to obtain an isothermal plunger pair; then the isothermal plunger pair is plasma composite titanium-carbonized to obtain a titanium-carbonized plunger pair; finally, the titanium-carbonized plunger pair is sequentially quenched, ice-cooled, and tempered to obtain a processed plunger pair.

[0063] Compared with the existing technology, this treatment method can enable the plunger pair to obtain a high hardness layer of TiC, and the matrix to obtain tempered needle-shaped, hidden needle martensite structure and fine particle carbide, maintain strength, thereby improving the wear and corrosion resistance of the plunger pair. It is a treatment method that greatly improves the resistance of parts.

[0064] Embodiment 2

[0065] Embodiment 2 of the present invention provides a treatment method for improving the wear resistance and corrosion resistance of a diesel engine plunger pair. This embodiment is an optimization based on the above embodiment. This embodiment takes a plunger pair made of GCr15 alloy as an example. The specific treatment method is as follows:

[0066] Step 1: Heat the processed GCr15 plunger pair to an austenitizing temperature of 750°C and keep it warm for 3 hours. Then cool it to 680°C with the furnace for isothermal treatment for 4 hours, slowly cool it to 650°C, take it out and air cool it to obtain the pre-treated structure.

[0067] Step 2: placing the plunger pair with fine spheroidal carbide structure obtained by pretreatment in a plasma metallization device for plasma composite titanium-carbon infiltration treatment;

[0068] Plasma composite titanium carburizing treatment is carried out and the treatment temperature is controlled at 780°C.

[0069] Plasma composite titanium carburizing treatment is carried out and the holding time is controlled at 3h.

[0070] Plasma composite titanium-carbon treatment requires the cathode voltage to be controlled at 600V and the source voltage to be controlled at 1000V.

[0071] Plasma composite titanium carburizing treatment is carried out, the furnace cooling temperature is controlled at 650°C and then air cooling is carried out.

[0072] Step 3: quench, cool and temper the sample obtained after plasma composite titanium carburizing treatment.

[0073] Embodiment 3

[0074] Embodiment 3 of the present invention provides a treatment method for improving the wear resistance and corrosion resistance of a diesel engine plunger pair. This embodiment is an optimization based on the above embodiment. This embodiment takes a plunger pair made of GCr15 alloy as an example. The treatment method includes:

[0075] Step 1: Heat the processed GCr15 plunger pair to an austenitizing temperature of 770°C and keep it warm for 2 hours. Then cool it to 700°C with the furnace for isothermal treatment for 3 hours, slowly cool it to 650°C, take it out and air cool it to obtain the pre-treated structure.

[0076] Step 2: placing the plunger pair with fine spheroidal carbide structure obtained by pretreatment in a plasma metallization device for plasma composite titanium-carbon infiltration treatment;

[0077] Plasma composite titanium carburizing treatment is carried out and the treatment temperature is controlled at 780°C.

[0078] Plasma composite titanium carburizing treatment is carried out and the holding time is controlled at 3h.

[0079] Plasma composite titanium-carbon treatment requires the cathode voltage to be controlled at 600V and the source voltage to be controlled at 1000V.

[0080] Plasma composite titanium carburizing treatment is carried out, the furnace cooling temperature is controlled at 650°C and then air cooling is carried out.

[0081] Step 3: quench, cool and temper the sample obtained after plasma composite titanium carburizing treatment.

[0082] The invention provides a treatment method for improving the wear resistance and corrosion resistance of a diesel engine plunger pair. The method comprises the following steps: performing composite titanium carburizing pretreatment on the plunger pair, then performing composite titanium carburizing treatment on the treated parts in a plasma manner, obtaining a surface TiC carburized layer and a matrix with a spherical carbide structure, then continuing to heat the parts to an austenitizing temperature for heat preservation treatment, then oil cooling the parts to room temperature and performing ice cooling treatment and tempering, so that the parts surface can obtain a high-hardness TiC carburized layer, the matrix can obtain a tempered needle-shaped, hidden needle martensite structure and fine particle carbide, and the strength can be maintained, thereby improving the wear resistance and corrosion resistance of the plunger pair. The invention is a simple and effective treatment method that greatly improves the resistance of the parts.

[0083] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A treatment method for improving the wear resistance and corrosion resistance of a diesel engine plunger pair, characterized in that: include: The plunger pair is heated to an austenitizing temperature of 750-790°C and kept at this temperature for a certain period of time to obtain an austenitized plunger pair; The plunger pair after austenitization treatment is cooled to 680-720°C in the furnace and is isothermally treated for a certain period of time, and then cooled to 650°C in the furnace and then taken out for air cooling to obtain the plunger pair after isotherm treatment; The plunger pair after the isothermal treatment is subjected to plasma composite titanium-carbon infiltration treatment to obtain a plunger pair after the titanium-carbon infiltration treatment; The plunger pair after the titanium carburizing treatment is sequentially subjected to quenching treatment, ice cooling treatment, and tempering treatment to obtain a processed plunger pair.

2. The method according to claim 1, characterized in that The step of heating the plunger pair to an austenitizing temperature of 750-790° C. and keeping the temperature for a certain period of time comprises: Heat the plunger assembly to the austenitizing temperature of 750-790°C and keep it at that temperature for no more than 3 hours.

3. The method according to claim 1, characterized in that The plunger pair after austenitization treatment is cooled to 680-720°C in the furnace and is isothermally treated for a certain period of time, and then cooled to 650°C in the furnace and taken out for air cooling to obtain the plunger pair after isothermally treated, including: The plunger pair after austenitizing treatment is cooled to 680-720°C and is isothermally maintained for no more than 4 hours, then cooled to 650°C in the furnace and then taken out for air cooling to obtain the plunger pair after isothermally treated.

4. The method according to claim 1 or 3, characterized in that: After the plunger pair after austenitization treatment is cooled to 680-720°C in the furnace and is isothermally treated for a certain period of time, it is then cooled to 650°C in the furnace and then taken out for air cooling to obtain the plunger pair after isotherm treatment, the method further includes: The end faces of the plunger pair after the isothermal treatment are polished and cleaned.

5. The method according to claim 1, characterized in that The step of subjecting the isothermally treated plunger pair to a plasma composite titanium-carbon infiltration treatment to obtain a titanium-carbon infiltration treated plunger pair comprises: The plunger pair after isothermal treatment is placed on a DC power supply support of a plasma metallization device and placed inside a cathode; Placing the titanium material and the carbon material on the auxiliary cathode structure, and making sure that the titanium material and the carbon material do not contact the plunger couple after the isothermal treatment; Inert gas is used as protective gas, and the gas pressure in the plasma metallization equipment is controlled within the range of 30-90Pa, the temperature is controlled at 780°C, the insulation time is 3 hours, the cathode voltage is 600V, the source voltage is 1000V, and the plunger pair after the isothermal treatment is subjected to plasma composite titanium-carbon treatment to obtain the plunger pair after titanium-carbon treatment.

6. The method according to claim 5, characterized in that: The inert gas is argon.

7. The method according to claim 5, characterized in that: The titanium material is in strip shape.

8. The method according to claim 5, characterized in that: The carbon material is graphite strip.

9. The method according to any one of claims 5 to 8, characterized in that: In the process of using inert gas as protective gas, controlling the gas pressure in the plasma metallization equipment within the range of 30-90 Pa, controlling the temperature at 780° C., holding time for 3 hours, cathode voltage at 600 V, source voltage at 1000 V, and subjecting the plunger pair after isothermal treatment to plasma composite titanium-carbon treatment to obtain the plunger pair after titanium-carbon treatment, the method comprises: The plunger pair after titanium carburizing treatment is furnace cooled to 650° C. and then air cooled.

10. The method according to claim 1, characterized in that The plunger pair after the titanium carburizing treatment is sequentially subjected to quenching treatment, ice cooling treatment, and tempering treatment to obtain a processed plunger pair, including: The temperature during quenching is controlled at 840°C; The temperature was controlled at -80°C during ice-cooling treatment; The temperature during tempering is controlled at 160°C.

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