Tribological system, comprising a valve seat ring and a valve

Abstract

A tribological system may include a valve seat ring composed of a sintered material and a valve having a surface at least in a seat region that may be at least one of (i) untreated, (ii) hardened, and (iii) plated. The sintered material may be a pressed and sintered powder mixture having a composition that may include (i) 5 to 45 wt % of at least one Fe-based hard phase, (ii) 0 to 2 wt % of each of graphite particles, MnS powder, MoS.sub.2 powder, and FeP powder, (iii) 0 to 7 wt % copper powder and 0 to 4 wt % Co powder, (iv) 0.1 to 1.0 wt % of a pressing aid, (v) a high-speed steel having a composition including 14-18 wt % Cr, 1.2-1.9 wt % C, 0.1-0.9 wt % Si, 0.5-2.5 wt % of each of V, W, and Mo, and (vi) a balance of Fe and production-related impurities in quantities of <1.5 wt %.

Claims

1. A tribological system, comprising: a valve seat ring composed of a sintered material; a valve having a surface at least in a seat region that is at least one of (i) untreated, (ii) hardened, and (iii) plated; wherein the sintered material is a pressed and sintered powder mixture having a composition including: 5 to 45 wt % of at least one Fe-based hard phase; 0 to 2 wt % graphite particles, 0 to 2 wt % MnS powder, 0 to 2 wt % MoS.sub.2 powder, and 0 to 2 wt % FeP powder; 0 to 7 wt % copper powder and 0 to 4 wt % Co powder; 0.1 to 1.0 wt % of a pressing aid; a balance of a high-speed steel having a composition including 14-18 wt % Cr, 1.2-1.9 wt % C, 0.1 to 0.9 wt % Si, 0.5 to 2.5 wt % V, 0.5 to 2.5 wt % W, and 0.5 to 2.5 wt % Mo, and a remainder of Fe and production-related impurities in quantities of <1.5 wt %; and wherein the at least one Fe-based hard phase has a composition including <0.2 wt % C, 26 to 32 wt % Mo, 8 to 12 wt % Cr, and 2.2 to 3 wt % Si.

2. The tribological system according to claim 1, wherein the remainder of Fe includes 0 to 40 wt % of a base powder of pure Fe and 0 to 40 wt % of a Fe-based powder.

3. The tribological system according to claim 1, wherein the composition of the pressed and sintered powder mixture further includes a Co-based hard phase in a proportion of 0.5 to 9.9 wt %.

4. The tribological system according to claim 1, wherein the valve is untreated in the seat region and is composed of at least one of Nimonic 80, Nireva 3015, and a nickel-based alloy.

5. The tribological system according to claim 4, further comprising a valve guide composed of a material complementary to the valve.

6. The tribological system according to claim 1, wherein the valve, at least in the seat region, is at least one of nitrided and plated with a material based on one of Fe and Co.

7. The tribological system according to claim 1, wherein the valve, at least in the seat region, includes a nitriding layer having a hardness >510 HV and a thickness >10 m.

8. The tribological system according to claim 1, wherein the valve, at least in the seat region, includes a plating layer having a layer thickness >200 m and at least one of a Co content and a Fe content >40%.

9. The tribological system according to claim 1, wherein the sintered material is infiltrated with a Cu-based infiltrant when it is sintered.

10. The tribological system according to claim 1, wherein the sintered material is heat treated after it is sintered.

11. The tribological system according to claim 1, wherein the production-related impurities include at least one of Ni, Cu, Co, Ca, and Mn.

12. The tribological system according to claim 1, wherein the at least one Fe-based hard phase includes a second Fe-based hard phase having a composition including <0.3 wt % C, 26 to 32 wt % Mo, 14 to 20 wt % Cr, and 2.9 to 4.2 wt % Si.

13. The tribological system according to claim 3, wherein the Co-based hard phase has a composition including 0.1 wt % C, 2.6 wt % Si, 8.5 wt % Cr, 28.5 wt % Mo, and 60.3 wt % Co.

14. The tribological system according to claim 3, wherein the Co-based hard phase has a composition including 0.2 wt % C, 1.3 wt % Si, 17 wt % Cr, 22 wt % Mo, and 59.5 wt % Co.

15. A tribological system, comprising: a valve seat ring composed of a sintered material; a valve having a surface at least in a seat region that is at least one of (i) untreated, (ii) hardened, and (iii) plated; wherein the sintered material is a pressed and sintered powder mixture having a composition including: 5 to 45 wt % of at least one Fe-based hard phase; 0 to 2 wt % graphite particles, 0 to 2 wt % MnS powder, 0 to 2 wt % MoS.sub.2 powder, and 0 to 2 wt % FeP powder; 0 to 7 wt % copper powder and 0 to 4 wt % Co powder; 0.1 to 1.0 wt % of a pressing aid; a balance of a high-speed steel having a composition including 14-18 wt % Cr, 1.2-1.9 wt % C, 0.1 to 0.9 wt % Si, 0.5 to 2.5 wt % V, 0.5 to 2.5 wt % W, and 0.5 to 2.5 wt % Mo, and a remainder of Fe and production-related impurities in quantities of <1.5 wt %; and wherein the at least one Fe-based hard phase has a composition including <0.3 wt % C, 26 to 32 wt % Mo, 14 to 20 wt % Cr, and 2.9 to 4.2 wt % Si.

16. The tribological system according to claim 15, wherein the composition of the pressed and sintered powder mixture further includes a Co-based hard phase in a proportion of 0.5 to 9.9 wt %, and wherein the Co-based hard phase has a composition including one of: 0.1 wt % C, 2.6 wt % Si, 8.5 wt % Cr, 28.5 wt % Mo, and 60.3 wt % Co; and 0.2 wt % C, 1.3 wt % Si, 17 wt % Cr, 22 wt % Mo, and 59.5 wt % Co.

17. A tribological system, comprising: a valve seat ring composed of a sintered material; a valve having a surface at least in a seat region that is at least one of (i) untreated, (ii) hardened, and (iii) plated; wherein the sintered material is a pressed and sintered powder mixture having a composition including: 5 to 45 wt % of at least one Fe-based hard phase; 0 to 2 wt % graphite particles, 0 to 2 wt % MnS powder, 0 to 2 wt % MoS.sub.2 powder, and 0 to 2 wt % FeP powder; 0 to 7 wt % copper powder and 0 to 4 wt % Co powder; 0.1 to 1.0 wt % of a pressing aid; a balance of a high-speed steel having a composition including 14-18 wt % Cr, 1.2-1.9 wt % C, 0.1 to 0.9 wt % Si, 0.5 to 2.5 wt % V, 0.5 to 2.5 wt % W, and 0.5 to 2.5 wt % Mo, and a remainder of Fe and production-related impurities in quantities of <1.5 wt %; and wherein the valve is untreated in the seat region and is composed of at least one of Nimonic 80, Nireva 3015, and a nickel-based alloy.

18. The tribological system according to claim 17, further comprising a valve guide composed of a material complementary to the valve.

19. The tribological system according to claim 17, wherein the at least one Fe-based hard phase has a composition including <0.2 wt % C, 26 to 32 wt % Mo, 8 to 12 wt % Cr, and 2.2 to 3 wt % Si.

20. The tribological system according to claim 17, wherein the at least one Fe-based hard phase has a composition including <0.3 wt % C, 26 to 32 wt % Mo, 14 to 20 wt % Cr, and 2.9 to 4.2 wt % Si.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The FIGURE illustrates results for total wear after engine testing under full load and a test duration of 100 hours, comparing the tribological system according to the present disclosure with comparison materials of Comparison 1 and Comparison 3.

DETAILED DESCRIPTION

(2) In the following, the invention will be described in greater detail with reference to embodiments.

Embodiment 1

(3) Table 1 lists the compositions of a powder mixture according to the invention, Invention, and a comparison mixture, Comparison 3. Production engineering and technical additives (e.g. sulfides) are included in Other. Some examples of mixture components that were used or usable within the scope of the invention are summarized in Table 2 (Starting powder).

(4) TABLE-US-00001 TABLE 1 Powder mixtures without solid lubricant, process-related additives and Cu infiltrant. K1 K2 Graphite K12 Cu K6 Wax Other Comparison 3 wt % 84 0.3 0.3 5 10 0.6 0.4 Invention wt % 84 0.3 0.3 5 10 0.6 0.4

(5) TABLE-US-00002 TABLE 2 Starting powders (in wt %) that are usable for mixtures according to the invention. The compositions listed are to be understood as average values from different shipments which may vary by approximately 10% to 30% in respect of final value and absolute content. Name C P Mn Si Cr Ni Mo Cu V W Co Fe Rest K1 1.0 0.4 0.4 4.0 5.0 3.0 6.0 1.0 78.9 K2 1.5 0.5 16.0 1.5 1.0 1.5 60.3 K3 0.8 0.04 0.3 0.45 4.0 0.4 5.0 0.4 2.0 6.2 1.0 Rest 3 K4 70 30 K5 4 0.5 1.5 Rest K6 0.1 2.6 8.5 28.5 50.8 K7 0.3 3.4 17.5 28.0 60.3 K8 0.1 2.6 8.5 28.5 60.3 K9 0.2 1.3 17.0 22.0 59.5 K10 3.4 17.5 28.0 51.1 K11 0.1 0.1 2.4 9.2 8.8 20.1 59 K12 15 85 K13 63 37 K14 100 Pressing 90.0 10 aids

(6) In a first step, the powders listed in Table 1 and specified in greater detail in Table 2 are mixed in a tumble mixer for 30 minutes. Then, these mixtures are compressed at a pressure of 700 MPa to make valve seat rings (a: 30 mm, i: 23 mm; height: 6 mm). A subset of the rings is sintered at a temperature from 1,110 to 1,125 C. (about 30 min) in N.sub.2H.sub.2 (17 to 25 vol % H.sub.2) in a continuous furnace. Another subset is subjected to sintering at 1,132 to 1,145 C. (approximately 30 minutes) in N.sub.2H.sub.2 (17 to 25 vol % H.sub.2).

(7) The sintering conditions employed and the sintering densities achieved are summarized in Table 3 (Sintered densities).

(8) TABLE-US-00003 TABLE 3 Sintering conditions for the powder mixture Invention according to the invention and the mixture for comparison Comparison 3. Sintering conditions and sintered density Tmax1 Duration Tmax2 Duration C. min C. min Comparison 3 1110-1125 20-33 1132-1145 20-33 Invention 1110-1125 20-33 1132-1145 20-33 Atmosphere: N2H2 (17-25 vol % H2)

(9) TABLE-US-00004 TABLE 4 Heat treatment for the powder mixture Invention according to the invention and the mixture for comparison Comparison 3. Variants of heat treatment after sintering Mixture Tempering Quenching and tempering for T Duration Cooling T Tempering Duration Cooling comparison C. h K/min h Duration Cooling C. min K/min Comparison 3 620 2 5-10 880 2 Oil 580 40 5-10 Invention 620 2 5-10 880 2 Oil 580 40 5-10

(10) The average diameters shown in Table 1 are obtained for the special carbides formed (MoC, VC, Cr.sub.2C.sub.3) because of the differing sintering conditions and the tempering (see Table 4).

(11) The maximum temperature during sintering was 1,132 to 1,145 C. The hold time at the temperature indicated above was 20 to 33 minutes. A mixture of N.sub.2H.sub.2 with an H.sub.2 content of 17-25% was used for the sintering atmosphere.

(12) After sintering, the sintered material underwent heat treatment as summarized in Table 4 (Heat treatment). For this purpose, both simple tempering at temperatures between 550 and 620 C. and a quenching and tempering process, i.e. hardening at 850 to 950 C.oil quenchingtempering at 510 to 610 C. were used. Since the differences in the properties, particularly in wear resistance, workability and creep properties are small, the tempered material is used.

(13) A measurement of the special carbides found an average diameter of 2.1 m in conventional comparative materials and 4.0 m in the sintered material according to the invention. The minimum and maximum values are given in addition to the average values in Table 5.

(14) TABLE-US-00005 TABLE 5 Average diameter of the special carbides in the sintered powder mixture Invention according to the invention and in the mixture for comparison Comparison 3. Average diameter [um] Min AVG Max Comparison 3 0.5 2.1 5.1 Invention 1.1 4.0 12.1

(15) In Table 6, both the hardness and the 0.2% compression yield strength are shown at room temperature and at 300 C. Surprisingly, the strength values of the sintered material according to the invention are similar to those of conventional material for comparison despite the coarser carbides (see Comparison 3, for example).

(16) TABLE-US-00006 TABLE 6 Strength characteristics and hardnesses after sintering/heat treatment of the powder mixture Invention according to the invention and the powder mixture Comparison 3 for comparison. Rd0.2 [Mpa] Hardness [HV10] T [ C.] Invention Comparison 3 Invention Comparison 3 25 1,400 1,813 415 391 300 1,328 1,195 372 349

(17) The performance is evaluated in a tribological system with regard to overall wear on the valve seat ring and the valve seat of a valve plated with Stellite F. Test results for the sintered/heat-treated valve seat ring-valve combinations of the powder mixture Invention according to the invention were compared against the comparison mixture Comparison 3 for comparison, and for two further mixtures which reflect the prior art.

(18) The test results indicate total wearafter engine testing in the Valve seat ring-Valve seat tribological system, wherein valve seat rings made from the comparison materials Comparison 1, Comparison 2 and Comparison 3 were considered as well as the valve seat ring prepared according to the invention (Invention).

(19) The test results illustrate the improved performance of the tribological system Invention according to the invention. With a skilful combination of the production and composition of the sintered material according to the invention and by combining a valve that has been plated at least in the seat region with Stellite F, the solid friction between tribological partners is reduced, thereby greatly lowering wear. The measured total wear is reduced in this case.

(20) The valve seat ring in the Comparison 1 tribological system consists of, in wt %: C: 1.5; S: 0.6; Cr: 3; Mo: 5 to 15; Cu: 10 to 20; V: 2; Fe: Balance; Other: 4.

(21) Comparison 2 is a Co-containing material which in addition to this expensive commodity also contains high levels of the refractory metals Mo and W. In detail, the functional region consists of the elements in wt %: C: 0.5 to 2; Mn: 1; Cr: 3 to 6; Mo: 8 to 15; Co: 16 to 22; W: 2 to 5; V: 1 to 3; Cu: 12 to 22; Fe: Balance; Other: 3.

(22) In the tribological systems Comparison 3, the valve seat ring has the following composition in wt %: C: 0.5 to 1.5; Si: 0.2 to 10; Cr: 2.5-5; Mo: 5 to 8; W: 3-6; V: 1 to 4; Cu: 10 to 20; Fe: Balance; Other: 3 and in Invention the VSR has the composition: C: 1 to 1.8; Si: 0.2 to 1.8; Mn: 0.6; Cr: 10 to 15; Mo: 2.5 to 4.5; V: 0.4 to 10; Cu: 0.8 to 1: 5; Fe: Balance; Other: 3.

(23) These are the material systems described above according to Tables 2 (Powder mixture and starting powder). The tribological systems Comparison 1 to Comparison 3 are based on conventional valve seat ring materials, wherein Comparison 1 was defined arbitrarily as having total wear of 100%.

(24) Unlike Comparison 1 to Comparison 3 the valve seat ring Invention contains significantly smaller amounts of expensive elements and achieves significantly lower overall wear.

Embodiment 2

(25) If the materials described in Embodiment 1 (Comparison 1, Comparison 3 and Invention) are compared in a test in which plated (F Stellite) and nitrided X50 valves are used as tribopartners, it is revealed after 100 hours of engine testing that the total wear (FIGURE) with a nitrided outlet valve is only slightly greater than that of a valve plated with inventive material. This tribological pairing is considerably superior to the standard commercial comparison materials Comparison 1 and Comparison 3. The FIGURE reproduces results for total wear after engine testing under full load and a test duration of 100 hours.

Embodiment 3

(26) In an motor test (500 h, hot and cold endurance) with uncoated or untreated Nimonic 80-outlet valves, the valve seat materials described in Embodiment 1 (Comparison 3 and Invention) exhibit very low total wear. The wear on the valve seat ring and the valve disc is so low that it is not measurable. On the material according to the invention (Invention), original machining marks are still visible. Since the material according to the invention is especially economical due to its use of small amounts of special carbides, a significant financial advantage over comparison material Comparison 3 is obtained with comparable technical performance (overall wear not measurable).