KR20180072876A - Nitrided sintered steels - Google Patents

Abstract

The present invention relates to a method of producing a sintered component, and to a sintered component by such a method. This method cost-effectively produces sintered steel parts with abrasion resistance similar to components made from cold cast iron.

Description

[0001] NITRIDED SINTERED STEELS [0002]

The present invention relates to a method of producing a sintered component by a single press and a single sintering, and to a sintered component produced by such a method. This method cost-effectively produces a sintered steel component with abrasion-resistant properties similar to components made from chilled cast iron.

In the industry, the use of metal products made by compaction and sintering of metal powder compositions is becoming increasingly prevalent. A number of other products of various shapes and thicknesses are being produced, and it is desirable to continue to increase quality requirements while at the same time lowering costs. Because a net shape component or nearly orthopotential component requiring minimal mechanical processing to reach the final shape is obtained by press and sintering of the iron-based powder composition with high material utilization , This technique has great advantages over conventional techniques for forming metal parts from bar stock, such as molding or machining, casting or forging.

It is desired to increase the performance of the sintered part so that more parts can be replaced with this cost-effective technique. Various industrial steel components, for example steel components in the automotive industry, have been successfully produced by press and sintering techniques. Automotive parts are manufactured in high volume for applications with stringent performance, design and durability requirements. Accordingly, the single-press and single-sintering techniques are well suited for the production of such components as long as the overall quality requirements can be met.

In the automotive industry, in the case of certain power train and valve train components, such as cam lobes, the requirements for abrasion resistance have so far become very difficult to convert to conventional sintered products . The main production techniques for these components currently include machining from Barstock, or casting to cold-drawn cast iron (CCI). In the case of small car cam lobes with slightly lower wear resistance requirements, these parts were successfully produced using double press / double sintering. However, until now, fabrication techniques including single pressing and single sintering have not been proven to provide abrasive properties similar to those of components made using CCI.

WO 2006/045000 discloses for cam lobes and other high wear articles made from iron-based powder metal mixtures of 0.5-3.0% Mo, 1-6.5% Cr, 1-5% V, and balance of Fe and impurities To carburized sintered alloys. However, wear resistance does not reach the same level as the CCI component.

Surprisingly, by using a specific iron-based powder alloy composition in combination with a warm die compaction and a nitriding process, a component having abrasion resistance similar to that of a component made with CCI can be produced Found.

More specifically, this can be achieved by a method of producing a sintered component by single-press and single-sintering, comprising the steps of:

a) at least one of Mn of less than 0.3% by weight, and 0.2-3.5% by weight of Cr, 0.05-1.20% by weight of Mo and 0.05-0.4% by weight of V and up to 0.5% of incidental impurities ), And a remaining amount of iron, the pre-alloyed iron-

b) mixing said pre-alloyed iron-based steel powder with a lubricant and graphite, and optionally a machining enhancing agent (s) and other conventional sintering additives,

c) compressing the mixed composition of step b) to a pressure of from 400 to 2,000 MPa to provide a compact,

d) sintering said compact from step c) in a reducing atmosphere at a temperature of from 1,000 to 1,400 ° C to provide a sintering component, and

e) nitriding the sintered component of step d) in a nitrogen-containing atmosphere at a temperature of 400 to 600 ° C with a soaking time of less than 3 hours.

The components produced according to this method exhibit abrasion-resistant properties similar to those of CCI-components. The present component has a hard case with a softer core and is therefore not through-hardened. The precured components can be more difficult to fabricate than a case hardened component with a softer core.

The method is particularly suited for automotive component work in an oil-lubricated environment, where the operating temperature is less than 250 占 폚, and the components have functions that require sliding movement. For example, cam lobes, sprockets, CVTs, and other power transmission devices, valve drive systems, and engine components. Of course, this method may also be suitable for producing components for other applications where good wear properties are desired.

Figure 1 is an IRG wear potential diagram showing three major wear areas: medium (safe) wear, limited wear and scuffing (severe adhesive wear).
2 shows the results of a wear test carried out using a commercial friction meter, a multi-purpose friction and abrasion measuring machine with crossed cylinder test setup.
3 shows the length of a wear track visually determined using an optical microscope.
Figure 4 shows the results from the evaluation of the test specimen at 2.5 m / s.
Figure 5 compares the composition CA before and after the nitridation step at three rates.
Figure 6 shows the metallurgical image of the nitrided specimen CA.
Figure 7 shows the hardness profile measured on Vickers (according to ISO 4498: 2005 and ISO 4507: 2000) of specimen CA.

Iron-based Alloyed  Manufacture of steel powder

The pre-alloyed iron-based steel powder provided in step a) of the process is preferably produced by water atomization of an iron melt comprising alloying elements. The atomized powder may be further processed by a reduction annealing process. The particle size of the pre-alloyed powder alloy can be any size as long as it is compatible with the press and sintering process. An example of a typical particle size is the particle size of a known powder ASC 100.29 available from Hoeganaes AB (Sweden) having a maximum of 2.0 wt%, greater than 180 [mu] m and 15 to 30 wt%, and less than 45 [mu] m. However, powders of thicker or finer particles can be used.

The use of coarse iron-based steel powders is becoming increasingly common in the field of powder metallurgy. Examples of such powders are iron-based powders having an average particle size of 75 to 300 [mu] m wherein less than 10% of the powder particles have a size of less than 45 [mu] m and the amount of particles of greater than 212 [mu] m is greater than 20%.

Finer iron-based steel powders may also be used. When using fine powders, such powders are preferably combined with binder (s) and / or flow agent (s) to provide better powder properties and compressibility. Such powders may have an average particle size in the range of, for example, 20 to 60 [mu] m.

Content of pre-alloyed steel powder

The pre-alloyed steel powder provided in step a) of the method is iron-based, comprising Mn, and at least one element selected from the group of Cr, Mo and V. The pre-alloyed steel powder may optionally further comprise Ni and / or additional strong nitride forming element (s), for example tungsten, titanium, niobium and / or aluminum.

The manganese (Mn) is present in an amount of 0.02 to 0.3 wt%. In practice, it is very difficult to achieve a content of less than 0.02% by weight when recycled scrap is used, in the event that no specific treatment for reduction which increases the cost is carried out during the steel making process. In addition, manganese increases the strength, hardness and hardenability of the steel powder, and accordingly has a manganese content of greater than 0.05 wt%, or preferably greater than 0.9 wt%. Mn contents exceeding 0.3 wt.% Will increase the formation of manganese inclusions in the steel powder and adversely affect compressibility due to solid solution hardening and increased ferrite hardness Will be. Accordingly, the Mn content should not exceed 0.3% by weight. The most preferred range for Mn is 0.1 to 0.3% by weight.

Chromium (Cr) is an alloying element and is provided for strengthening the matrix by solid-solution curing. Chromium also increases the hardenability and abrasion resistance of the sintered body. In addition, Cr is a very strong nitride former, thereby promoting nitriding. If chromium is added, it should be added in an amount of at least 0.2% by weight, preferably at least 0.4% by weight, and more preferably at least 1.3% by weight in order to have the desired effect on the properties of the sintering component. However, in the case of increasing the addition of chromium, the requirements of the controlled atmosphere during sintering are increased, making the component more expensive. Thus, when chromium is added, it should be at most 3.5 wt.% Cr, preferably at most 3.2 wt.% Cr. In a preferred embodiment, the chromium content is 0.4 to 2.0 wt%, more preferably 1.3 to 1.9 wt%. In another preferred embodiment, the chromium content is from 2.8 to 3.2% by weight.

Molybdenum (Mo) stabilizes the ferrite after sintering. If molybdenum is added, it should be added in an amount of at least 0.1% by weight, preferably at least 0.15% by weight, in order to have the desired effect on the properties of the sintering component. It is not desired to have a Mo-content that is too high, because too high a Mo-content will not contribute sufficiently to performance. Accordingly, when molybdenum is added, it should be at most 1.2 wt% Mo, preferably at most 0.6 wt% Mo. In some embodiments, the steel may be essentially free of Mo, or may have an Mo content of less than 0.1 wt%, preferably less than 0.05 wt%.

Vanadium (V) increases strength by precipitation hardening. Vanadium is also a strong nitride forming element, with a grain size refining effect. When vanadium is added, it should be added in an amount of at least 0.05 wt.%, Preferably at least 0.1 wt.%, More preferably at least 0.25 wt.%, In order to have the desired effect on the properties of the sintering component . However, high vanadium content facilitates oxygen pickup and thereby increases the oxygen level in the component produced by the powder, which is not desired in too high a quantity. Accordingly, the vanadium content should be at most 0.4% by weight, preferably at most 0.35% by weight.

Pre-alloyed steel powders are optionally selected from the group of additional strong nitride forming element (s) known in the art, such as tungsten (W), titanium (Ti), niobium (Nb) and aluminum And may further include one or more element (s). When added, the total amount of any of the additional strong nitriding element (s) should be from 0.05 wt% to 0.50 wt%, preferably from 0.1 wt% to 0.4 wt%, and more preferably from 0.15 wt% to 0.30 wt% .

Nickel (Ni) increases strength and hardness while providing good ductility properties. However, nickel is an expensive element and is avoided as much as possible. When added, the content is kept low. The pre-alloyed steel powder may optionally contain Ni in an amount of 0.1 wt.% To 1.0 wt.%, Preferably 0.1 wt.% To 0.5 wt.%. In a preferred embodiment, the pre-alloyed steel powder is essentially free of nickel, so that the pre-alloyed steel powder contains less than 0.1 wt% nickel, preferably less than 0.05 wt% nickel.

The oxygen (O) is at most 0.25 wt%. Too high a content of oxygen impairs the strength of the sintered component and compromises the compressibility of the powder. For this reason, O is preferably at most 0.18 wt%. In fact, when using the water jetting technique, it is difficult to reach an oxygen content of less than 0.1% by weight. Accordingly, the oxygen content in the water dispersed and annealed powders is generally in the range of 0.10 to 0.18 wt%.

The carbon (C) in the steel powder should be at most 0.1 wt.%, Preferably less than 0.05 wt.%, More preferably less than 0.02 wt.%, And nitrogen (N) at most 0.1 wt.%, Preferably less than 0.05 wt. Should be less than 0.02% by weight. The higher the content of carbon and nitrogen, the more unacceptable the compressibility of the powder will be.

An arbitrary element selected from the group consisting of copper (Cu), phosphorus (P), silicon (Si), sulfur (S), and any other element is added to each of the inevitably contained impurity elements, Is preferably less than 0.15 wt.%, Preferably less than 0.10 wt.%, More preferably less than 0.05 wt.%, And most preferably less than 0.1 wt.%, In order to prevent degradation of the compressibility of the steel powder or act as a formative agent of harmful inclusions. 0.03 wt.% Of each element. The total sum of all inevitably contained impurities should be less than 0.5% by weight, preferably less than 0.3% by weight, more preferably less than 0.2% by weight.

Preferred embodiments of the pre-alloyed steel powder

In a preferred embodiment, the pre-alloyed steel powder according to the invention consists of the following elements (wt.%):

Fe: residual quantity

Mn: 0.09 - 0.3

Cr: 1.3-1.9

Mo: 0 - 0.3

And an inevitably contained impurity of up to 0.3.

In another preferred embodiment, the pre-alloyed steel powder according to the invention consists of the following elements (wt.%):

Fe: residual quantity

Mn: 0.09 - 0.3

Cr: 1.3-1.6

Mo: 0.15 - 0.3

And an inevitably contained impurity of up to 0.3.

In another preferred embodiment, the pre-alloyed steel powder according to the invention consists of the following elements (wt.%):

Fe: residual quantity

Mn: 0.09 - 0.3

Cr: 1.5 - 1.9

Mo: 0 - 0.1

And an inevitably contained impurity of up to 0.3.

In another preferred embodiment, the pre-alloyed steel powder according to the invention consists of the following elements (wt.%):

Fe: residual quantity

Mn: 0.09 - 0.3

Cr: 2.8-3.2

Mo: 0.4 - 0.6

And an inevitably contained impurity of up to 0.3.

In another preferred embodiment, the pre-alloyed steel powder according to the invention consists of the following elements (wt.%):

Fe: residual quantity

Mn: 0.09 - 0.3

V: 0.05 - 0.4

Mo: 0 - 0.1

And an inevitably contained impurity of up to 0.3.

Powder composition

Prior to compression, the pre-alloyed steel powder is mixed with a lubricant, graphite, optionally one or more machining enhancer (s), and optionally other conventional additives, such as hard phase materials.

In order to improve the strength and hardness of the sintered component, carbon is incorporated into the matrix. Carbon is added to the composition as graphite in an amount of 0.15 to 1.0 wt% of the composition. An amount less than 0.15 wt% will cause very low strength, and an amount greater than 1.0 wt% will result in excessive formation of carbide, adversely affecting nitride formation properties. Preferably, the graphite is added in an amount of 0.20 to 0.80 wt%, and more preferably 0.30 to 0.60 wt%.

The lubricant is added to the composition to facilitate ejection of the compressed and compressed components. The addition of less than 0.05% by weight of the lubricant to the composition will not have a significant effect and the addition of more than 2% by weight of the composition will make the density of the compacted body too low. Preferably, the amount of lubricant added is 0.3 to 0.8 wt% of the composition, more preferably 0.4 to 0.6 wt% of the composition. Any type of lubricant suitable for compression may be used. The lubricant may be selected from the group of metal stearates, waxes, fatty acids and derivatives thereof, oligomers having a lubricating effect, polymers and other organic materials.

In one embodiment, composite lubricating particles suitable for compression into a heated mold, such as 10 to 60 wt% of at least one primary fatty acid amide having 18 to 24 carbon atoms and 40 to 90 wt% Composite lubricating particles comprising a core of at least one fatty acid bisamide are selected and the lubricating particles also comprise nanoparticles of at least one metal oxide attached to the core.

In a preferred embodiment, the composite lubricating particles suitable for compression into a heated mold comprise from 10 to 30% by weight of at least one primary fatty acid amide and from 70 to 90% by weight of at least one fatty acid bisamide. The at least one fatty acid bisamide is preferably selected from the group consisting of methylene bisoleamide, methylenebisstearamide, ethylenebisoleamide, hexylenebisstearamide, and ethylene bisstearamide. Nanoparticles of at least one metal oxide is _{preferably, Ti0 2, Al 2 0 3} , Sn0 2, Si0 2, is selected from the group consisting of Ce0 _2, and indium titanium oxide.

Copper (Cu) is an alloy element commonly used in powder metallurgy technology. Cu will improve strength and hardness through employment of hardening. Cu will also promote the formation of a sintering neck during sintering as a copper melt before reaching a sintering temperature which provides so-called liquid phase sintering. The powder may optionally be mixed with Cu, preferably in an amount of 0.2 to 3 wt% Cu. In a preferred embodiment, no copper is added to the composition at all.

Nickel (Ni) increases strength and hardness while providing good ductility properties. However, a content of greater than 1.5% by weight will tend to form Ni-rich austenite during the heat treatment conditions and will degrade the strength of the material. The powder may optionally be mixed with Ni in an amount of 0.1 to 1.5% by weight. In a preferred embodiment, the composition is not mixed with nickel.

The machining enhancer (s) may optionally be incorporated into the composition in an amount of 0.1 to 1.0% by weight of the composition. If it is less than 0.1% by weight, its effect is not sufficiently good, and if it exceeds 1.0% by weight, no further improvement is added. Preferably, when mixed, the machining enhancer (s) is mixed in an amount of 0.2 to 0.8% by weight of the composition, more preferably 0.3 to 0.7% by weight of the composition. The machining enhancer (s) are preferably selected from the group consisting of MnS, MoS ₂ , CaF ₂ , and / or phyllosilicates such as kaolinite, smectite, bentonite and mica (e.g., Muscovite or phlogopite). ≪ / RTI > In working conditions, the machining enhancer (s) also act as a solid lubricant, thereby helping to increase the abrasion resistance of the component.

Other conventional sintering additives, such as hard phase materials, may optionally be incorporated into the composition.

compression

The iron-based powder composition is transferred to a press mold and treated at a compression pressure of 400 to 2,000 MPa, preferably 500 to 1,200 MPa. In a preferred embodiment, the mold in the press is heated to a temperature between 40 and 100 캜, preferably between 50 and 80 캜 before and during compression. This technique is referred to as "warm die compaction" or "heated die compaction ". The component is preferably compressed to a green density of at least 7.10 g / cm3, preferably at least 7.15 g / cm3, more preferably at least 7.20 g / cm3.

Due to the choice of lubricant and compression process, high green densities can be achieved, ensuring high sintered density without undue dimensional changes. This provides good tolerance and closed porosity of the sintered components.

Sintering

The green component obtained is further sintered at a temperature of about 1,000 to 1,400 ° C in a reducing atmosphere. In a preferred embodiment, the components are sintered at typical sintering temperatures ranging from 1,000 to 1,200 ° C, preferably from 1,050 to 1,180 ° C, most preferably from 1,080 to 1,160 ° C. However, according to the requirement, the components may also be sintered at higher temperatures, for example in the range of 1,200 to 1,400 ° C, preferably 1,200 to 1,300 ° C, and most preferably 1,220 to 1,280 ° C.

The component is sintered to a density in the range of 7.1 to 7.6 g / cm3, preferably 7.15 to 7.50 g / cm3, more preferably 7.20 to 7.45 g / cm3. However, it is also possible to sinter at a density higher than 7.6 g / cm < 3 >.

Post-sintering treatment

The sintered component is then treated with a nitridation process to obtain the desired microstructure. The nitridation process is carried out in a nitrogen-containing atmosphere at a temperature of approximately 500 캜. In a preferred embodiment, the nitridation process is carried out in a mixture of nitrogen and hydrogen gas at 400 to 600 占 폚, preferably 470 to 600 占 폚, with a soaking time of less than 3 hours, preferably less than 2 hours, more preferably less than 1 hour, Deg.] C to 580 [deg.] C. However, the soaking time during the nitriding process is preferably at least 10 minutes, more preferably at least 20 minutes.

Optionally, other general types of nitridation processes may be used, such as, but not limited to, carbonitriding and nitrocarburizing.

Often, when sintering components are gas nitrided, the sintering component must first be steam-treated to close the pores and regulate nitrogen penetration, since excessive nitrogen penetration into the components can result in a fragile structure. However, this step is not necessary when providing the component according to the present invention, since the sintering density achieved is high enough to ensure closed porosity. Thus, the component may be nitrided in a controlled manner without previous steam-treatment steps.

Using the method of the present invention, the surface of the component is coated with a nitride-rich so-called white layer or compound layer with a thickness of 1 to 20 탆, preferably 5 to 15 탆, and a depth of approximately 1 to 6 mm, preferably 1 to 4 mm Lt; RTI ID = 0.0 > cured < / RTI >

Properties of the final component

The components made according to the present invention achieve high abrasion resistance in sliding lubricated contacts. Achieved abrasion resistance is similar to components made of chilled cast iron.

The sintered component has a closed porosity immediately after sintering to eliminate the need for steam treatment prior to gas nitridation.

Also, components manufactured by the claimed method include deeper surface porosity as compared to CCI-components, although not wishing to be bound by any particular theory, it is believed that this is due to the fact that during working conditions, It is believed to provide a lubricating effect because of the presence of the enhancer.

In a preferred embodiment, the nitride final component is 0.5 to 1 mm depth of hardness of the core more than twice the hardness, and preferably the core hardness is more than _{0 .05} 600 MHV 300 MHV when approximately _{0 .05,} preferably ₀ 700 MHV It has a hardness of greater than _0.05, or when the core hardness be approximately 350 MHV 700 MHV _{0.05 0 .05} excess, preferably greater than 800 MHV _{0 .05.} The overall case depth should be 0.5 to 4.0 mm, preferably 1.0 to 3.0 mm, more preferably 1.5 to 2.5 mm.

The term core hardness will be understood as the hardness value at the center of the component prior to nitridation. The term total case depth will be understood as the distance from the surface of the component if the hardness value equals the core hardness value.

According to the test method described in the embodiment section, the final component should exhibit good abrasion resistance in lubricating sliding contact. When tested at a sliding speed of 2.5 m / s for 100 seconds, the component is safe for hertzian pressure of at least 800 MPa, preferably at least 900 MPa, and more preferably at least 1,000 MPa wear.

Example

Test Methods

The general characterization of the wear in the lubricated sliding contact was carried out by the researchers in the linked international plane in the Informal IRG-WOEM group supported by the OECD in 1980. Several co-coordinated investigations have provided the severity of the valuable results that IRG-wear transitions diagrams may be the most important (see Figure 1).

The IRG wear potential diagram (FIG. 1) shows three major wear areas: medium (safe) wear, limited wear and scuffing (severe adhesive wear). This wear is mainly dependent on the relative sliding speed between the contact surfaces, as well as other factors such as lubrication mode, lubricant chemistry, surface roughness, i.e. topography, surface metallurgy, and contact bodies. Other alloys will have similar curves at different pressures, and Figure 1 is just an illustrative example.

An automotive cam lobe for sliding contact with a cam follower is a good example of a component that is carried in use at a sliding speed of about 0.1 m / s to 3 m / s or higher. In 1988, the literature [Chatterley [TC Chatterley, "Cam and Cam Follower Reliability", SAE Paper No. 885033, 1988] summarized the MIRA engine test bench testing of several cold cast (CCI) cam lobes for CCI, coated and boron treated ceramic follower. At the 800 MPa hertz level there was no breakage for most test drives, but at the 1,000 MPa level, only the CCI passed for the SiN ceramic test combination.

In addition to the above, abrasion tests in these investigations were carried out at three sliding speeds, i.e. 0.1, 0.5 and 2.5 m / s, with standard engine oil (see Table 1) at 90 DEG C as a lubricant. At 2.5 m / s, the test was performed by sequentially increasing the Hertz pressure until scuffing occurred.

The abrasion test was carried out using a commercial friction meter, a multi-purpose friction and abrasion measuring machine with cross-cylinder test setup (FIG. 2). The friction meter applies a vertical load on the cylinder specimen holder by a dead weight / load arm while the AC thyristor controlled motor drives the counter ring. The counter ring was immersed in an oil bath with approximately 25 ml oil and an option to heat up to 150 < 0 > C. The PC controls the test and records the contact, wear, friction and linear displacement of the oil temperature. The obtained linear displacement is about three times larger than the linear wear over the wear track because the displacement transducer is placed on the load arm lever rather than being placed across the test cylinder. The Hertz pressure is proportional to the linear wear (h) of the cylinder sample and also to the length (a) of the wear track. The length (a) can be visually determined using an optical microscope, as shown in Fig.

Table 1 describes the properties of the lubricating oil used during the wear test.

Table 1. Lubricant used in the wear test

Table 2 describes pre-alloyed steel powders used in the tests.

Table 2. Used pre-alloyed steel powders

Distaloy (TM) DC-1, Astaloy (TM) CrL and Astaloy ( TM ) 85 Mo are well known powder metallurgy pre-alloyed steel powders available from Hoeganaes AB ( www.hoganas.com ). Powder C was produced in the same manner as Astaloy ™ 85 Mo and Astaloy ™ CrL.

Test specimens for these investigations are sintered test specimens and reference cast iron specimens as outlined in Table 3 and Table 4.

Table 3. Reference Specimen

Table 4. Specimens produced by powder metallurgy

*) MnS is a machining agent available from Hoeganaes AB ( www.hoganas.com ), Kenolube ™ is a compressive lubricant available from Hoeganaes AB, C-UF4 is available from Graphit Kropfmuehl AG ( www.grahite.de) ). ≪ / RTI >

Figure 4 shows the results from the evaluation of the test specimen at 2.5 m / s. Surprisingly, it can be seen that all specimens produced in accordance with the present invention reach levels comparable to reference standards R1 and R2, that is, the chilled cast iron reference. Comparison of the reference C-R with the inventive C-A, C-B and C-C clearly demonstrates how efficient the novel process of producing sintered components by virtue of a single press / single sintering actually is.

In addition, the composition C-A was compared before and after the nitridation step at three rates. The results are shown in Table 5.

Table 5. Wear test results for C-A

In Table 5, it can be seen that the nitridation step is essential for the nature of the material. Already at a level of 320 MPa hertz, the components which were not carried out in the nitriding step e) and which were treated with a) to d) of the claimed method only showed severe wear. On the other hand, the components first treated in steps a) to e) exhibited severe wear at 1,100 MPa, a considerably higher hertz level. The results of Table 5 are plotted in FIG.

6 shows a metallurgical image of the nitrided specimen C-A. The white nitride-rich layer is visible on the sintered surface, which provides high adhesive abrasion resistance, as can be seen from the results.

Figure 7 shows the hardness profile measured in Vickers (according to ISO 4498: 2005 and ISO 4507: 2000) of specimen CA. As can be seen from these figures, the hardness was _greater than 700 MHV _0.05 at a depth of 1 mm, thus forming a case having a hardness twice as high as the core.

Claims (13)

a) at least one of Mn of less than 0.3 wt.%, and 0.2 to 3.5 wt.% Cr, 0.05 to 1.20 wt.% of Mo and 0.05 to 0.4 wt.% of V, and inevitably contained impurities of up to 0.5 wt.%, Providing a pre-alloyed iron-based steel powder comprising an amount of iron,
b) mixing the pre-alloyed iron-based steel powder with a lubricant and graphite and optionally a machining enhancing agent (s) and other conventional sintering additives,
c) compressing the mixed composition of step b) to a pressure of from 400 to 2,000 MPa to provide a compact,
d) sintering said compact from step c) in a reducing atmosphere at a temperature of from 1,000 to 1,400 ° C to provide a sintered component, and
e) nitriding said sintered component of step d) at a temperature of 400 to 600 占 폚 in a nitrogen-containing atmosphere with a soaking time of less than 3 hours. A method of producing a sintered component by single sintering. The lubricating composition of claim 1 wherein the lubricant is a composite lubricant particle comprising from 10 to 60% by weight of at least one primary fatty acid amide having from 18 to 24 carbon atoms and from 40 to 90% by weight of at least one core of fatty acid bisamide Wherein the lubricating particles further comprise nanoparticles of at least one metal oxide deposited on the core. 3. Process according to claim 1 or 2, in which the compact is not steamed before nitriding in step e). 4. The process according to any one of claims 1 to 3, wherein in step c) the compact is compressed to a green density of at least 7.10 g / cm3. 4. The process according to any one of claims 1 to 3, wherein in step d) the sintered component is sintered at a density of 7.1 to 7.6 g / cm3. 6. The method of any one of claims 1 to 5, wherein the pre-alloyed iron-based steel powder further comprises from 0.1 wt% to 1.0 wt% Ni. 6. The method according to any one of claims 1 to 5, wherein Ni is essentially absent in the pre-alloyed iron-based steel powder. The method of any one of claims 1 to 7, wherein the pre-alloyed iron-based steel powder comprises from 0.05% to 0.50% by weight of tungsten (W), titanium (Ti), niobium (Nb) Al). ≪ / RTI > 6. Method according to any one of claims 1 to 5, characterized in that the pre-alloyed iron-based steel powder is present in a weight percentage,
Fe: residual quantity
Mn: 0.09 - 0.3
Cr: 1.3-1.6
Mo: 0.15 - 0.3
And at most 0.3 inevitably contained impurities. 6. Method according to any one of claims 1 to 5, characterized in that the pre-alloyed iron-based steel powder is present in a weight percentage,
Fe: residual quantity
Mn: 0.09 - 0.3
Cr: 1.5 - 1.9
Mo: 0.1 max
And at most 0.3 inevitably contained impurities. 6. Method according to any one of claims 1 to 5, characterized in that the pre-alloyed iron-based steel powder is present in a weight percentage,
Fe: residual quantity
Mn: 0.09 - 0.3
Cr: 2.8-3.2
Mo: 0.4 - 0.6
And at most 0.3 inevitably contained impurities. 6. Method according to any one of claims 1 to 5, characterized in that the pre-alloyed iron-based steel powder is present in a weight percentage,
Fe: balance,
Mn: 0.09 - 0.3
V: 0.05 - 0.4
Mo: 0.1 max
And at most 0.3 inevitably contained impurities. Safe wear for hertzian pressure of up to at least 800 MPa, preferably at least 900 MPa, and more preferably at least 1,000 MPa, when tested at a sliding speed of 2.5 m / s for 100 seconds, A nitrated, sintered component produced according to any one of claims 1 to 12 having abrasion resistance in a lubricating sliding contact which provides an abrasive sliding contact.

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