GB2227031A

GB2227031A - Surface treated sliding or rolling contact element and rolling bearing

Info

Publication number: GB2227031A
Application number: GB8927196A
Authority: GB
Inventors: Sasaki Masami; Koichi Hachiya
Original assignee: NSK Ltd
Current assignee: NSK Ltd
Priority date: 1988-12-01
Filing date: 1989-12-01
Publication date: 1990-07-18
Anticipated expiration: 2009-12-01
Also published as: FR2640009B1; FR2640009A1; GB8927196D0; GB2227031B

Abstract

An element suitable for sliding-contact or rolling-contact, has a surface covered by a film of a 0.05 mu m to 0.5 mu m thickness of reaction product by a chemical treatment. The element has a low friction property, low wear property, improved load carrying capacity and improved seizure resistance. The reaction product film may be a metal phosphate, a metal sulphide, a metal chloride and may be formed by reaction at the surface with at least one of organophosphorus compounds, organosulphur compounds, organochlorine compounds and organometallic compounds. In specific examples the following treating solutions are used:- tridecyl acid phosphate (1, 2, 3); zinc hydrozarbyl dithiophosphate (4); tert-octyl disulphide (5); n-octyl chloride (6); a mixture of trioctyl phosphate, tridecyl acid phosphate and di-tert-octyl disulphide (7).

Description

SURFACE TREATED SLIDING OR ROLLING CONTACT ELEMENT AND ROLLING BEARING BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sliding or rolling contact element which is surface treated in order to reduce friction and wear between the contacting surfaces of two elements in sliding or rolling contact with each other and increase the load carrying capacity and seizure resistance of each of the two elements. It also relates to a rolling bearing employing the rolling contact element.

2. Description of the Related Art In normal bearing lubrication, friction coefficient between two sliding or rolling contact surfaces of metal bodies changes with absolute viscosity of used lubricating oil, bearing load and rotational speed between the two sliding or rolling contact surfaces. In complete or full fluid lubrication in which a thick and continuous film of oil is formed in the interface between the two sliding or rolling contact surfaces, a contact between the underlying surfaces of the two metal bodies will not almost take place so that the friction coefficient of the two sliding or rolling contact surfaces is very low.In mixed lubrication in which metal-metal contact partially takes place or boundary lubrication in which a lubricant oil film is broken thereby to cause a few patches where metal-metal contact takes place, it is possible that a surface damage, e.g., seizure of sliding or rolling contact surfaces to be lubricated takes place. In order to prevent this damage, various types of lubricant additive (e.g., an oiliness agent, an extreme-pressure agent and an antiwear agent) have been employed.

The interface between the contacting surfaces of the two metal bodies is at high temperature and high pressure so as to be in high reactive condition. A lubricant additive (the organic compound with chlorine, sulfur or phosphorus, e.g., chlorinated paraffin, dibenzyl sulfide or tricresyl phosphate) introduced into the area of contact readily reacts with a bearing metal.

As s result of reaction, inorganic or organometallic compounds with each element (e.g., metal chloride, metal sulfide, metal phosphate etc.) are produced on the contacting surfaces of the two metal bodies. The reaction products are considered to prevent the seizure and wear between the contacting surfaces of the two metal bodies.

However, an immediate effect of lubricant additive could not be anticipated since a considerable time is required up to the start of a reaction between the lubricant additive and the contacting or frictional surfaces of the two metal bodies.

In the prior art, there are some examples in which a sliding or rolling contact element is previously surface treated with the lubricant additive, e.g., tricresyl phosphate (i.e., TCP).

However, there has been yet no established theory of the effect that the sliding or rolling contact element is previously surface treated with the lubricant additive, so that this effect is variously estimated.

In particular, this effect under a severe condition in which a supply of lubricating oil is frequently interrupted during operation of the sliding or rolling contact element has not been discussed. That is, the thickness of a surface treated layer of the lubricant additive formed on the sliding or rolling surface by the prior art is as thin as below 0.05,m measured by X-ray photoelectron spectroscopy (i.e., XPS, described later). The present inventors carried out superhigh speed four ball test in order to study an improvement in lubricating property of bearing caused by such a thin surface treated layer. This superhigh speed four ball test is a kind of extreme-pressure test essentially equal to ASTM D-2783.

The rotational speed of the vertical shaft of a superhigh speed four ball tester can be increased up to 20,000 rpm while that of an four ball tester according to ASTM D-2783 can be increased up to 1,770 rpm. The superhigh speed four ball test disclosed that the surface treated layer such thin as below 0.05 j'm would not improve the extreme-pressure property, in particular, under the severe condition in which, e.g., the supply of lubricating oil was interrupted.

Another surface treatment of the bearing metal with an inorganic compound, e.g., zinc phosphate or manganese phosphate instead of the above mentioned reaction product of lubricant additive has been attempted. In this case, there is a problem in that this inorganic compound causes a corrosion in the bearing metal surfaces. In addition, the thickness of the surface treated layer of this inorganic product is above 0.5 Am. The superhigh speed four ball test applied to this surface treated layer of the inorganic product disclosed that the surface treated layer of this inorganic product failed to improve the extreme-pressure property.

Thus, the prior art failed to sufficiently disclose an effective thickness of the surface treated layer formed on each of the two contacting surfaces, so that a sufficient improvement in the lubricating property caused by the surface treatment applied to the sliding or rolling contact element was not achieved.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems. An object of the present invention is to provide a sliding or rolling contact element and a rolling bearing having a low friction property, low wear property, load carrying capacity and seizure resistance that are sufficiently improved.

In order to achieve this object, the metal surface of the sliding or rolling contact element is chemically treated so that a 0.05 /!m to 0.5glum thick reaction product film is formed on the surface of the sliding or rolling contact element. The reaction product film means an inorganic and/or organometallic compound of a submicron thickness which is produced by a chemical reaction between a chemically active organic compound and the metal surface of the sliding or rolling contact element and which possesses a characteristic different from that the bulk or underlying body of the sliding or rolling contact element.

The thickness of the reaction product film preferably is in the range of 0.05 #.Lm to 0.3 [ Lm and in particular, 0.1 "m.

Above mentioned reaction product film is made of at least one of phosphorus, sulfur and chlorine compounds.

That is, the reaction product film is made of at least one of inorganic and/or organometallic films which are produced by reactions between organic compounds (organophosphorus compounds, organosulfur compounds, organochlorine compounds, and organometal compounds) and a metal of the sliding or rolling contact element. In particulur, the reaction product film preferably is produced from a reaction between a mixture of organophosphorus compound and organosulfur compoud and the sliding or rolling contact element.

The film of the reaction product with phosphorus element comprises reaction product films produced by reactions between at least one of phosphite esters, phosphate esters and acid phosphate esters and the metal of the sliding or rolling contact element.

The film of the reaction product with the sulfur element comprises reaction product films produced by reactions between at least one of sulfurized fat and oil, sulfurized olefin, mercaptans, sulfides, sulfoxides and sulfones and the metal of the sliding or rolling contact element.

The film of the reaction product with the chlorine element comprises reaction product films produced by reactions between chlorinated paraffins and/or chlorinated fats and oils and the metal of the sliding or rolling contact element.

The film of the organometal reaction product with the orgnometal comprises reaction product films produced by reactions between at least one of metal dihydrocarbyl dithiophosphates, metal dihydrocarbyl dithiophosphates and naphthenic acid metal salts and the metal of the sliding or rolling contact element.

A rolling bearing of the present invention has at least one of a retainer, inner and outer races and rolling element made of the rolling contact elements having various reaction product films of the present invention.

According to the present invention, at least one of two contacting surfaces of the sliding or rolling contact elements is subjected to a chemical treatment so that a 0.05 !.Lm to 0.5 ,!m thick reaction product film is formed on that contacting surface. A sliding or rolling contact element and rolling bearing of the present invention has a low friction property, low wear property, and sufficiently improved load carrying capacity and seizure resistance.

BRIEF DESCRIPTION OF THE DRAWING FIG.1 is a graph illustrating one example of a measurement of the thickness of a film of a phosphorus-containing reaction product with phosphorus element of the present invention.

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, the present invention will be described in detail. The thickness of the reaction product film is measured by an X-ray photoelectron spectrophotometer (abbreviated to XPS). The XPS transmits X-ray to a sample surface and analyzes the energy of a photoelectron emitted from the outermost surface (--,several A) to produce data of a surface element and chemical state. Also, the XPS measures the thickness of the reaction product film while an argon (Ar) ion gun spatters the surface of the sample, thereby to analyze the distribution in depth of the element of the reaction production film.

FIG.1 is a graph illustrating one example of the measurement of the thickness of the reaction product film produced by the organophosphorus compound (e.g., tridecyl acid phosphate). The thickness of the reaction product film is defined in terms of the depth profile of the sample taken by the XPS immediate before the phosphorus content of the reaction product film is unchanged (as shown in FIG.1, an Ar+ etching time is 27 min). In this case, since the etching rate is 3 nm/min, the thickness of the reaction product film is about 0.8gem (i.e., 27 min x 3 nm/min).

Controls of the concentration of the compound in solution, reaction temperature and reaction time of a reaction between a compound and the sliding or rolling contact element carried out in response to the kind of the compound can cause to adjust the thickness of the reaction product film as defined above.

The reaction product film was formed by a reaction between the sliding or rolling contact element and at least one of the organophosphorus compound, organosulfur compound, organochlorine compound and organometallic compound. The reaction product film which is produced by a reaction between the sliding or rolling contact element and the organophosphorus compound is referred to as the organophosphorus compound-reaction product film. The reaction product film which is produced by a reaction between the sliding or rolling contact element and the organosulfur compound is referred to as the organosulfur compound-reaction product film. The reaction product film which is produced by a reaction between the sliding or rolling contact element and the organochlorine compound is referred to as the organochlorine compound-reaction product film.The reaction product film which is produced by a reaction between the sliding or rolling contact element and the organometallic compound is referred to as the organometallic compound reaction product film.

The organophosphorus compound used for producing the organophosphorus compound-reaction product film comprises phosphite esters, phosphate esters and acid phosphate esters.

The phosphite esters comprise phosphite esters derived from C1 to C18 hydrocarbyl groups (e.g., alkyls, phenyls benzyls, cresyls, cinnamyls and aryls). For example, trioctyl phosphite, triphenyl phosphite, tricresyl phosphite, bis-2-ethyl hexyl phosphite, tridecyl phosphite, dibuthyl hydrogen phosphite, tris(nonyl phenyl) phosphite, dilauryl hydrogen phosphite, diphenyl monodecyl phosphite, trilauryl trithiophosphite and diphenyl hydrogen phosphite are preferable.

The phosphate esters comprise phosphate esters derived from C1 to C20 hydrocarbyl groups. For example, triphenyl phosphate, triethyl phosphate, tributhyl phoshate, tris(2-ethyl hexyl) phosphate, tridecyl phosphate, diphenyl mono(2-ethyl hexyl) phosphate, tricresyl phosphate, trioctyl phosphate, tristearyl phosphate are preferable.

The acid phosphate esters comprise C1 to C20 mono-or dihydrocarbyl acid phosphates. For example, methyl acid phosphate, isopropyl acid phosphate, buthyl acid phosphate, 2-ethyl hexyl acid phosphate, isodecyl acid phosphate, tridecyl acid phosphate, lauryl acid phosphate are preferable.

The organosulfur compound used for producing the organosulfur compound-reaction product film comprises sulfurized fatts and oils (e.g., sulfurized sperm oil, sulfurized olefin), mercaptans, sulfides, sulfoxides and sulfones.

The olefin sulfides comprise sulfides derived from C3 to C8 olefin sulfides or low molecular-weight polyolefin sulfides derived from C3 to C8 olefins. For example, penten sulfide, buthylene sulfide and octene sulfide are preferable.

The mercaptans comprise C4 to C20 alkyl mercaptans and C4 to C20 mercaptofatty esters. For example, n-butyl mercaptan, isobutyl mercaptan, tertiary butyl mercaptan, n-octyl mercaptan, tertiary nonyl mercaptan, tertiary dodecyl mercaptan, butyl thioglycolate, ethyl thiopropinate and octyl 3-mercaptopropionate are preperable.

The sulfides comprise monosulfides (-S-) with C4 to C20 hydrocarbyl groups, disulfides (-S-S-) with C4 to C20 hydrocarbyl groups, and polysulfides (-S-S-S-) with C4 to C20 hydrocarbyl groups. For example, dibutyl monosulfide, dibutyl disulfide, diphenyl sulfide and dibenzyl sulfide are preferable.

The sulfoxides comprise sulfoxides with C4 to C20 hydrocarbyl groups. For example, dibutyl sulfoxide and dibenzyl sulfoxide are preferable.

The sulfones comprise sulfones with C4 to C20 hydrocarbyl groups. For example, dibutyl sulfone, didodecyl sulfone and phenyl sulfone are preferable.

The organochlorine compound used for producing the organochlorine compound-reaction product film comprises chlorinated paraffins and chlorinated fatts and oils.

The chlorinated paraffins comprise, e.g., n-octyl chloride, paraffin chloride, octadecyl chloride. The chlorinated fatts and oils comprise, e.g., chlorinated sperm oil.

The organometallic compound used for producing the organometallic compound-reaction product film comprises metal dihydrocarbyl dithiophosphates, metal dihydrocarbyl dithiocarbamates and naphthenates.

The metal dihydrocarbyl dithiophosphates comprise the group of metal dihydrocarbyl dithiophosphates each of which includes one of C4 to C20 hydrocarbyl groups. For example, zinc dimethyl dithiophosphate, zinc butyl isooctyl dithiophosphate, zinc di(4-methyl-2-pentyl) dithiophosphate, zinc di(tetrapropenyl phenyl) dithiophosphate, zinc (2-ethyl-1-hexyl) dithiophosphate, zinc (isooctyl) dithiophosphate, zinc (ethyl phenyl) dithiophosphate, zinc (amyl) dihiophosphate, and zinc di(hexyl) dithiophosphate. In addition to the above zinc dihydrocarbyl dithiophasphates, lead(Pb), cadmium(Cd), antimony(Sb) and molybdenum(Mo) dihydrocarbyl dithiophosphates are preferable.

The metal dihydrocarbyl dithiocarbamates comprise the group of metal dihydrocarbyl dithiocarbamates each of which includes one of C4 to C20 hydrocarbyl groups. For example, zinc dimethyl dithiocarbamate, zinc butyl isooctyl dithiocarbamate, zinc di(4-methyl-2-pentyl) dithiocarbamate, zinc di(tetrapropenyl phenyl) dithiocarbamate, zinc (2-ethyl-1-hexyl) dithiocarbamate, zinc (isooctyl) dithiocarbamate, zinc (ethyl phenyl) dithiocarbamate, zinc (amyl) dithiocarbamate and zinc di(hexyl) dithiocarbamate. In addition to the above#zinc dihydrocarbyl dithiocarbamates, lead(Pb), cadmium(Cd), antimony(Sb) and molybdenum(Mo) dihydrocarbyl dithiocarbamates are preferable.

The naphthenates comprise naphthenic acid metal salt. For example, lead naphthenate is preferable.

The various compounds producing the reaction product films may be employed directly or under a condition in which the compounds are dissolved in oil or a solvent and diluted in a concentration range of 0.1 to 100 wt%. For example, refined paraffinic oil and diphenyl oil may be employed as the oil and benzene, toluene, hexane and the like may be employed as the solvent. Nonpolar oils and solvents are preferable.

In the formation of the reaction product film, the organophosphorus compound, organosulfur compound, organochlorine compound and organometallic compound of a predetermined concentration were employed alone or in a mixture thereof. In particular, it was found that when the organophosphorus compound and organosulfur compound were mixed, an interaction therebetween promoted a formation rate of the reaction product film. In the same kind of organophosphorus compound, organosulfur compound or organochlorine compound, corresponding specific organic compounds were used separately or in combination.

In response to the kind and content of each of the specific organic compounds used separately or in combination, a corresponding reaction product film containing phosphorus, sulfur, chlorine, organic metal or at least two of these elements is formed on the surface of the sliding or rolling contact element.

The sliding or rolling contact element to be treated is immersed in a solution of the organophosphorus compound, organosulfur compound, organochlorine compound, organometallic compound or a mixture thereof the concentration of which is adjusted to be above-described predetermined value. The reaction between the metal of the sliding or rolling contact element and this organic compound proceeded for a predetermined period of time in the range of 0.5 hr to 8 hr so that a reaction temperature is controlled to a predetermined level in the range between a room temperature and 120 0C. Thus, the reaction product film of a 0.05 /#m to 0.5 llm thickness was formed on the surface of the sliding or rolling contact element.In other words, the concentration of the solution of this organic compound, the temperature and time of the reaction between the metal of the sliding or rolling contact element and the solution of this organic compound are controlled so that the thickness of the reaction product film formed on the sliding or rolling contact element falls within the range of 0.05 /lm to 0.5 ,glum.

In the formation process of the reaction product film, the use of ultrasonic wave under the condition of a predetermined temperature improved the uniformity of the reaction product film and increased the rate of the reaction between the metal of the sliding or rolling contact element and the organic compound.

The superhigh speed four ball test was applied to rolling contact elements which were surface treated and had reaction product films of various thicknesses formed on the surfaces of the rolling contact elements. When the thickness of each of the reaction product film was below 0.05 glm and above 0.5 /tom, the seizure between the surfaces of the rolling contact elements and an oscillation took place.On the other hand, when the thickness of that reaction product film was in the range of 0.05 [ im to 0.5lem and in particular, preferably 0.05 Am to 0.3 I.tm, the superhigh speed four ball test experimentally disclosed that very good results in the low friction property, low wear property, load carrying capacity and seizure resistance of the rolling contact element were obtained.

At least a single sliding or rolling contact surface of the sliding or rolling contact element may be subjected to the surface treatment of the present invention. Of course, other portions of the sliding or rolling contact element may be also subjected to the surface treatment of the present invention. When the contacting surface of at least one of two sliding or rolling contact elements is subjected to the surface treatment of the present invention, the sufficiently improved low friction property, low wear property, load carrying capacity and seizure resistance are obtained.

DESCRIPTION OF THE EXAMPLES Example 1 Bearing steel balls of a 1/2 inch diameter having respective reaction product films of six thicknesses produced by phosphate ester were prepared. Then, the superhigh speed four ball test was applied to the bearing steel balls of Example 1. Tridecyl acid phosphate (i.e., a mixture of tridecyl monoacid phosphate and tridecyl diacid phosphate) having a high-reactivity was employed as phosphate ester.

The composition and physical properties (e.g., mechanical strength, adherence, uniformity and lubrication property) of each of the reaction product films depends on the chemical structure of hydrocarbyl group of acid phosphate ester (R=C1 to C20, this ester may be an aliphatic or aromatic compound or a mixture thereof) and the concentration in oil or a solvent. The thickness of each of the reaction product films depends on a surface treatment temperature and time. Therefore, conditions of the reaction between the bearing steel balls and the tridecyl acid phosphate were determined in view of the concentration, surface treatment temperature and time.

In Example 1, the steel balls were immersed in a solution in which tridecyl acid phosphate was diluted by a refined oil to have a 5 wt% concentration and reacted with the solution at 40 OC for 4 hr, so that a reaction product film of an about 0.3 glm thichness was formed on the ball surfaces.

Thus, reaction temperature and time were controlled so that the reaction product films of 0.01 A'm, 0.05 Asm, 0.1/lem 0.3 item, 0.5 /lm and 0.8 Am thicknesses were formed on the ball surfaces, respectively.

The following Table 1 shows the results of the superhigh speed four ball test applied to the samples which are surface treated.

In Example 1, the rotational speed was increased till the speed to cause seizure at rate of 1000 rpm/min under oil temperature shown in Table 1 and load.

Table 1

oil Max Hertg Seizure occurrence temperature0C pressure rotational speed rpm GPa Untreated 120 3.0 6,000 0.01 flm 120 3.0 7,000 0.05 rum 120 3.0 10,000 0.1 gm 120 3.0 12,500 0.3 ,#m 120 3.0 11,000 0.5 m 120 3.0 10,000 0.8 sm 120 3.0 great oscillation The seizure resistance of the bearing steel ball having the reaction product film of a 0.01/lm thickness order was essentially equal to that of the surface-untreated bearing steel ball.The seizure resistance of the bearing steel ball having the reaction product film of the 0.8 /#m thickness failed to be measured since a great oscillation took place.

On the other hand, the seizure resistance of each of the bearing steel balls having the reaction product films of 0.05 Am to 0.5 tlm thicknesses was significantly increased. In particular, the seizure resistance of the bearing steel ball having the reaction product film of 0.1 m thickness was best.

Example 2 Bearing steel balls of the 1/2 inch diameter having respective reaction product films of six thicknesses produced by the same phosphate ester as in Example 1 were prepared. Then, the superhigh speed four ball test was applied to the bearing steel balls of Example 2.

In Example 2, a supply of lubricating oil was interrupted. This interruption was carried out as follows: 1) A 1-minute break-in was carried out at the pv value of 2 600 kgf/mm .m/s in oil bath of which temperature was 120 C.

2) After the passage of 1 minute, the lubricating oil of the oil bath was immediately exhausted and a period of time up to the occurrence of a seizure of the bearing steel ball was measured. The following Table 2 shows the results of the superhigh speed four ball test: Table 2

Time up to occurrence of seizure Untreated 0'00" O.Olstm O'40" 0.05 ,im 1'40" 0.1 /zm 3'00" 0.3 gem 2'27" 0.5 /.tm 2'00" 0.8 Pm 1'00" When the thickness of the reaction product film was 0.8 {lem, a great oscillation took place during operation of the superhigh speed four ball tester and the bearing steel ball experienced a large friction.On the other hand, when the thickness of the reaction product film was 0.05!lm, the friction coefficient of the bearing steel ball was relatively low.

Eeven under a severe condition in which lubricating oil was exhausted, it was apparent that the effect of each of the reaction procuct films formed on the surface of the bearing steel ball was very advantageous. In particular, the seizure resistance of the bearing steel ball having the reaction product film of 0.1 !jim thickness was best.

Example 3 Tapered rollers of steel of a tapered roller bearing (the outer diameter: 52 mm and the inner diameter: 25 mm) having respective reaction product films of various thicknesses produced by the same phosphate ester as in Example 1 were prepared. Then, a temperature increase of the bearing having each of the tapered rollers was measured under conditions of 100 N radial load, a 1,500 N axial load, a 3,000 rpm rotational speed and very small content of oil, i.e., oil plating.

The following Table 3 shows the results of the bearing tapered roller of Example 3: Table 3

Temperature increase of outer race (deg.C) Untreated 100 0.01 jim 98 0.1 llm 60 0.3 jim 72 0.5 jim i 74 0.8 ,! m i 97 great oscillation Also in temperature increase, it was apparent that the temperature increase of each of the tapered rollers having the reaction product films of 0.1 jim to 0.5 jim thicknesses was about 30 to 40 deg.C lower than those of the untreated tapered roller and the tapered rollers having the reaction product films of 0.01/lem and 0.8,!lm. In particular, the temperature increase of the tapered roller having the reaction product film of 0.1 jim thickness was best to reflect a low friction of the reaction product film of 0.1 ,!m thickness. Such results were also obtained on a ball bearing.

Example 4 Zinc hydrocarbyl dithiophosphate including 20.7 % sulfur in a molecule thereof was diluted in a refined oil to have a 1 wt% concentration therein. The bearing steel ball of the 1/2 inch diameter was immersed in this zinc hydrocarbyl dithiophosphate solution and reacted at 120 0C for 24 hr. Thus, the reaction product film of o.l am thickness was produced.

A period of time up to the occurrence of a seizure was measured on the sample thusly produced under the same conditions as in Example 2. This measurement provided a 1'10" seizure occurrence time.

Example 5 Tert-octyl disulfide, a disulfide including two sulfurs in a molecule thereof, is diluted in a refined oil so as to have a 50 wt% concentration. The 1/2 inch bearing steel ball was immersed in the tert-octyl disulfide solution and reacted at 600C for 4 hr. Thus, the reaction product film of 0.1 jim thickness was formed on the surface of the 1/2 inch bearing steel ball. A period of time up to the occurrence of a seizure was measured on the sample thusly produced under the same conditions as in Example 2.

This measurement provided a 1'30" seizure occurrence time.

Example 6 N-octyl chloride was diluted by a refined oil so as to have a 50 wt% concentration. The 1/2 inch bearing steel ball was immersed in this n-octyl chloride solution and reacted at 60 OC for 4 hr. Thus, the reaction product film of 0.1 jim thickness was formed on the surface of the 1/2 inch bearing steel ball. A period of time up to the occurrence of a seizure was measured on the sample thusly produced under the same conditions as in Example 2. This measurement provided a 1'35" seizure occurrence time.

Example 7 Since it was found that the organosulfur compound and organophosphorus compound interacted with each other so that a reaction for forming the reaction product film was promoted, the 1/2 inch bearing steel ball was immersed in a mixture of a 5 wt% trioctyl phosphate, a 5 wt% tridecyl acid phosphate constituting a kind of acid phosphoric and a 5 wt% di-tert-octyl disulfide and reacted at 60 0C for 2 hr.

Thus, the reaction product film of 0.1 jim thickness was formed on the surface of the 1/2 inch bearing steel ball.

A period of time up to the occurrence of a seizure was measured on the sample thusly produced under the same conditions as in Example 2. This measurement provided a 3'20" seizure occurrence time. This value is better than that of Example 2.

Example 7 discloses that even when different organic compounds were mixed to form the reaction product film on the surface of the sample, the sliding or rolling contact element with this film had a good seizure resistance.

The surface treatment of the present invention is applicable not only to the ball or roller of the rolling bearing but also to, e.g., the groove surfaces of the inner and outer races and the retainer surface of the rolling bearing. A rolling bearing comprising at least one of these elements had a very good load carrying capacity and seizure resistance, thereby was sufficiently employed even under a severe condition in which a supply of lubricating oil was interrupted during operation of the rolling bearing.

Claims

CLAIMS:

1. An element suitable for sliding-contact or rollingcontact with a film of a 0.05 Bm to 0.5 Bm thickness at one surface which is the reaction product of a chemical treatment at that surface.

2. An element as claimed in claim 1 wherein the thickness of said reaction product film is between 0.OSijm and 0.3cm.

3. An element as claimed in claim 1 wherein the thickness of said reaction product film is O.1#m.

4. An element as claimed in claim 1, 2 or 4 wherein the reaction product film comprises at least one of metal phosphates. metal sulfides and metal chlorides.

5. An element as claimed in claim l, 2 or 3 wherein said reaction product film is formed by reaction at the surface with at least one of organophosphorus compounds, organosulfur compounds, organochlorine compounds and organometallic compounds.

6. An element as claimed in claim 5, wherein said reaction product film is formed by reaction at the surface of a mixture of at least one organophosphorus compound and at least one organosulfur compound.

7. An element as claimed in claim 5 wherein the said reaction product film is an organophosphorus reaction product film formed by reaction at the surface with at least one of phosphite esters, phosphate esters and acid phosphate esters.

8. An element as claimed in claim 7, wherein the organophosphorus reaction product film is formed by the reaction at the surface of tridecyl acid phosphate.

9. An element as claimed in claim 5 wherein said reaction product film is an organosulfur reaction product film formed by reaction at the surface with at least one of sulfurized fats and oils, sulfurized olefins, mercaptans, sulfides, sulfoxides and sulfones.

10. An element as claimed in claim 9 wherein the organosulfur reaction product film is formed by reaction at the surface with di-tert-octyl disulfide.

11. An element as claimed in claim 5 wherein said reaction product film is an organochlorine reaction product film and is formed by reaction at the surface with at least one of chlorinated paraffins, chlorinated fats, and chlorinated oils.

12. An element as claimed in claim 11 wherein said organochlorine reaction product film is formed by reaction at the surface with n-octyl chloride.

13. An element as claimed in claim 5 in which the reaction product film is an organometallic reaction product film and is formed by reaction at the surface of at least one of metal dihydrocarbyl dithiophosphates, metal dihydrocarbyl dithiocarbamates and metal naphthenates.

14. An element as claimed in claim 13, wherein the organometallic reaction product film is formed by reaction at the surface with zinc dihydrocarbyl dithiophosphate.

15. An element as claimed in claim 6, wherein the reaction product film is formed by reaction at the surface with a mixture of tridecyl acid phosphate and di-tert-octyl disulfide.

16. A rolling bearing, wherein at least one of a retainer, an inner race, an outer race and a rolling element is an element with a rolling-contact surface as claimed in any one preceding claim.