GB2246145A

GB2246145A - Nickel-born alloy composite slidable surface

Info

Publication number: GB2246145A
Application number: GB9109588A
Authority: GB
Inventors: Takeji Tsuchiya; Katsuaki Ogawa; Motonobu Onoda
Original assignee: Nippon Piston Ring Co Ltd
Current assignee: Nippon Piston Ring Co Ltd
Priority date: 1990-07-18
Filing date: 1991-05-02
Publication date: 1992-01-22
Also published as: GB9109588D0

Abstract

Slidable members, such as piston rings and cylinder liners made from cast iron or steel, have their slidable surfaces coated with a composite nickel-boron plate which is composed of a nickel alloy matrix containing 0.1 to 10 wt.% boron, and 5 to 30 vol.% of solid particles dispersed in the matrix. The particles are hard particles and/or solid-lubricant particles 0.1 to 10 mu m in diameter. The boron in the nickel alloy matrix increases hardness, and improves abrasion-, seizure- and corrosion-resistance.

Description

SLIDABLB MEMBER The present invention relates to a slidable member having a slidable surface coated with a composite nickel plate.

Slidable members, such as piston rings and the like for use in an internal combustion engine, are subjected in service to a high load at high temperatures, so that they are mostly coated with a hard chrome plate to improve their anti-abrasion property. However, chrome plating is costly. The reasons for this are that it needs a long time for treatment and that it discharges pollutant water which must be purified at a high cost. Furthermore, the chrome plate is soon dfgraded in anti-abrasion, anti-seizure, and anti-corrosion when mounted in a high lead-content gasoline engine, To solve the problems, such a composite plate is shown in JP B 56-18080 that has a nickel-phosphorus alloy matrix and hard particles of nitrides, carbides, and oxides dispersed in the matrix. The composite plate has good anti-abrasion, anti-seizure, and anti-corrosion properties when the particles are selected properly in sort, size, and amount, and available to coat the slidable surface of such a member as a cylinder liner and a piston ring.

However, the composite plate as described above becomes somewhat brittle when subjected to such a high load under high temperatures that dominate in an internal combustion engine during high speed running. The slidable member coated with the composite plate is still insufficient in anti-abrasion, anti-seizure, and anti-corrosion for use with the high speed engine, It would therefore be desirable to be able to provide a slidable member coated with an improved composite plate that is sufficient in anti-abrasion, anti-seizure, and anti-corrosion for use with a high speed engine in which severe conditions dominate.

The present invention provides a slidable member which comprises a oetal surface coated with a composite plate which is compose of a nickel alloy matrix containing 0. 1 to 10%, by weight, of boron and 5 to 30X, by volume, of (e. g. hard and/or solid-lubricant) particles dispersed in the matrix.

The particles are selected to have a diameter not more than 10 Fm, preferably le s than 10 ym.

Boron, contained in the nickel alloy matrix, is effective to increase the hardness of plate and improve the plate in anti-abrasion, anti-seizure, and anti-corrosion. It is added by an amount of 0. 1 to 10X by weight. The reasons for this are that less than 0. 1% of boron has no effect and that more than 10% of boron oakes the plate rather brittle and has a negative effect on inpact strength and adhesion.

As hard particles dispersed in the nickel alloy matrix, one or more is selected from amont Sis4, SiC, NC. AI, Os, ZrO2, Cr2Os and the like. As solid lubricant particles, one or more is selected froc long sulfides, borides, and self-lubricating synthetic resins. In preference, the particles are of 0. 1 to 10 . diameter and dispersed in the matrix by an amount of 5 to 30X, by volume. hhen the particles are of less than 0. 1 FLm or dispersed in the matrix by an amount of less than 5X by volute, they may not improve the plate in anti-abrasion, When they are of more than 10 m diameter or dispersed in the matrix by an amont of sore than 30 X by volume, the plate may deteriorate in strength and give an abrasion to the other slidable member.

Advantages which may be achieved are that the plated slidable webers are superior both in anti-abrasion and in anti-scuffing and they are suitable for use with a high speed internal combustion engine in which dominate very severe conditions. The plated slidable member reduces the cost for production because it is available without beat-treatment or with heat-treatmsntat relatively low temperatures.

In theaccompanying drawings: FIG. 1 is a graph illustrating the results of a hardness test before and after heat-treatoent ; FIG. 2 is a graph illustrating the results of an abrasion test; and FIG. 3 is a graph illustrating the results of a scuffing test.

The following are examples of the slidable member of the present invention, in which trioethylaoine-borane is called "TMAB".

BXAMPLBS: (1) Plating Condition texperature : 55 C pH : 3. 5 electric current density : 5A/doz (2) Bath Composition Coaparison 1 : nickel sulfate 240 grams/liter nickel chloride 45 grams/liter boric acid 30 graos/liter silicon nitride 100 graws/liter (Si2N4, 0.7 m average diameter) Comparison 2 : hypophosphorous acid 3. 0 grams/liter added to the composition of Comparaison 1 Example 1 : TMAB 6. 0 grams/liter added to the composition of Comparison 1 Example 2 : nickel sulfate 240 graos/liter nickel chloride 45 grams/liter boric acid 30 grams/liter boron nitride 100 grams/liter (BN, 2. 0 m average diameter) TMAB 6. 0 graos/liter Bxample 3 : TMAB 6. 6 graas/liter molybdenum disulfide 100 graos/liter (MoS2, 0,1 m average diameter) added to the composition of Comparison 1 The respective composite plates were deposited fro the Comparisons and Examples. The same hard plate can be obtained from the bath prepared by adding TMAB to the composition of Comparison 1 from which boric acid is removed. However, the bath desirably includes boric acid to maintain its useful life and stability.

HARDNBSS TEST : The individual plates obtained from the five above-mentioned baths were tested with Micro Vickers Hardness Tester before and after being subjected to one-hour heat-treatment at preselective temperatures. The test results are plotted in PIG, 1 The results show that the plates froo Comparisons 1 and 2 having no boron additives are insufficient in hardness without being heat-treated and that the plate from Comparison 1 remarkably reduces its hardness when treated at temperatures of higher than 300 C. On the other hand, the plate from Bxample having boron additives has a sufficient hardness without being heat-treated and maintins its hardness after being heat-treated at temperatures of 300 to 350 C. This means that the addition of boron compound also improves the plate in heat-resistance The plate from Comparison 2 containing phosphorous additives is better than that from Comparison 1 containing no phosphorus additives. But, it is inferior in hardness to the plate from Example before being heat-treated This means that the bath containing the boron additives is more advantageous than the bath containing the phosphorus additives to deposit a composite plate on the slidable member. The sliding member plated in Comparisons would not be used under severe conditions without heat-treated at temperatures of 350 to 380 C The inventive member plat-ed in Examples can be used under severe conditions without being heat-treated or after heat-treated at a temperature of 300 C or less, resulting in an avantage that the plating cost is reduced, ABRASION TBST : The slidable members plated in Comparisons 1 and 2 and the Exampleswere tested under an abrasion condition as shown in Table 1. In Assoler tester, the test piece (18 an X 12 as X 6 mm) is fixed while the rotary contact piece is doughnut-shaped with 40 on outer diameter, 16 mm inner diameter, and 10 thickness, The plate on the test piece was arranged to be in contact with the plate on the rotary piece The test results are plotted in FIG. 2.

TABLB 1 : ABRASION TEST CONDITION tester AMSLER ABRASION TESTER oethod rotary piece contact half immersed in oil and loaded rotary contact piece FC25 (HRB 98) lubricating oil 1030 oil temperature room temperature peripheral speed 0. 89 m&num; (500 rp) load 60 kg test time 3 h abrasion amount difference in level (JL m) zetsured by a contact profile meter SCUFFING TEST : The slidable webers obtained from Cozparison8 1 and 2 and Example were tested for anti-scuffing under a scuffing condition as shown in Table 2. The results are plotted in PI6 3. It shows that the plate from the inventive bath. containing Ni-B-SiaN4 is superior in anti-scuffing to those from Comparisons 1 and 2 containing Ni-Si2N4 and Ni-P-Si. N4 TABLE 2 : SCUPFFING TEST CONDITION tester HIGH-SPEED FRICTIONAL ABRASION TBSTBR type rotary-disc flat-contact sliding-friction rethod suspending the supply of lubricating oil after 20 minute breaking-in with 25 kg/ct'planar pressure, entering test with 30 kg/cm2. incresing the pressure by 10 kt/cwa, every 2 minute running until scuffing occurs in which the final planar pressure is determined as the limit. rotary disc made from FC aterial paired piece FC25 (HRB98) lubricating oil SAEt30 (50X) and white kerosene (50%) oil amont 0. 02 liter/rin oil texperature 50 C (inside tank) peripheral speed 3. 75 m/s (300 rp) From foregoing, the preferred slidable member has its slidable surface coated with a composite plate of the type having a nickel-boron alloy matrix and hard and/or solid-lubricant type particles dispersed in the matrix. The composite plate will not become brittle under a high load at high temperatures in which the conventional plate with a nickel-phosphorus alloy matrix becomes brittle, The slidable members of the invention, such as piston rings and cylinder liners made from cast iron or steel and coated with the composite nickel-boron plate, are superior both in anti-abrasion and in anti-scuffing and advantageously suitable for use with a high speed internal combustion engine in which dominate very severe conditions.

Claims

Claims:1. A slidable member comprising a slidable surface coated with a composite plate composed of a nickel alloy matrix containing 0.1 to 10 wt. % boron, and 5 to 30 vol. % solid particles with a diameter of not more than 10 pm dispersed in the matrix.
2. A slidable member as claimed in claim 1, wherein the particles have a diameter of 0.1 to 10 Jum.
3. A slidable member as claimed in claim 1 or 2, wherein the particles comprise hard particles.
4. A slidable member as claimed in claim 1 or 2, wherein the particles comprise solid-lubricant particles.
5. A slidable member as claimed in claim 1 or 2, wherein the particles comprise hard and solid-lubricant particles.
6. A slidable member as claimed in any preceding claim, wherein the amount of particles is not more than 10 vol. %.
7. A slidable member as claimed in any preceding claim, being a piston ring or a cylinder liner.
8. A slidable member substantially as described with reference to any of Examples 1 to 3.