1、Designation: B895 15B895 16Standard Test Methods forEvaluating the Corrosion Resistance of Stainless SteelPowder Metallurgy (PM) Parts/Specimens by Immersion in aSodium Chloride Solution1This standard is issued under the fixed designation B895; the number immediately following the designation indica
2、tes the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 These test methods cover a procedure for ev
3、aluating the ability of sintered PM stainless steel parts/specimens to resistcorrosion when immersed in a sodium chloride (NaCl) solution.1.2 Corrosion resistance is evaluated by one of two methods. In Method 1, the stainless steel parts/specimens are examinedperiodically and the time to the first a
4、ppearance of staining or rust is used to indicate the end point. In Method 2, continuedexposure to the sodium chloride solution is used to monitor the extent of corrosion as a function of time.1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are include
5、d in this standard.1.4 This standard does not purport to address the safety concerns, if any, associated with its use. It is the responsibility of theuser of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitationsprior to use.2. Re
6、ferenced Documents2.1 ASTM Standards:2A380 Practice for Cleaning, Descaling, and Passivation of Stainless Steel Parts, Equipment, and SystemsB243 Terminology of Powder MetallurgyB528 Test Method for Transverse Rupture Strength of Powder Metallurgy (PM) SpecimensD610 Practice for Evaluating Degree of
7、 Rusting on Painted Steel SurfacesD1193 Specification for Reagent WaterG1 Practice for Preparing, Cleaning, and Evaluating Corrosion Test SpecimensG48 Test Methods for Pitting and Crevice Corrosion Resistance of Stainless Steels and RelatedAlloys by Use of Ferric ChlorideSolution3. Terminology3.1 De
8、finitionsUseful definitions of terms for metal powders and powder metallurgy are found in Terminology B243.4. Summary of Test Method4.1 Method 1 is recommended for evaluating the corrosion resistance of stainless steel powder metallurgy parts/specimens andto verify that proper materials and processi
9、ng conditions were used.4.1.1 In this method, parts/specimens are immersed in 5 % (by mass) NaCl solution and examined periodically until the firstappearance of staining or rust. A part or specimen is considered to have reached the end point when the first sign of corrosionoccurs.4.2 Method 2 is rec
10、ommended for evaluating the processing variables used in producing parts/specimens.4.2.1 In this method, parts/specimens are exposed further to the NaCL solution and periodically rated as either A, B, C, or D(A-no corrosion; D-high or extreme corrosion) by comparison with Fig. 1, a photograph of cor
11、roded specimens which serves as1 These test methods are under the jurisdiction of Committee B09 on Metal Powders and Metal Powder Products and is the direct responsibility of Subcommittee B09.05on Structural Parts.Current edition approved Oct. 1, 2015April 1, 2016. Published November 2015April 2016.
12、 Originally approved in 1999. Last previous edition approved in 20102015 asB895 05B895 15.(2010)1. DOI: 10.1520/B0895-15.10.1520/B0895-16.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume i
13、nformation, refer to the standardsstandards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to
14、adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright A
15、STM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1a standard. Additional examples of quantitative ratings may be found in Test Method D610. Method 2 has been found useful inalloy screening and process optimization studies.5. Significance and Use5.
16、1 The ability of sintered powder metallurgy stainless steel parts/specimens to resist corrosion when immersed in sodiumchloride solution is important to their end use. Causes of unacceptable corrosion may be incorrect alloy, contamination of the partsby iron or some other corrosion-promoting materia
17、l or improper sintering of the parts (for example, undesirable carbide and nitrideformations caused by poor lubricant burnoff or improper sintering atmosphere).5.2 This standard may be part of a purchase agreement between the PM parts producer (seller) and the user of the parts(purchaser) (Method 1)
18、. It may also be used to optimize part or specimen production parameters (Method 2).6. Apparatus6.1 Sealable Glass or Plastic Jars, of suitable capacity for specimens to be completely covered by the NaCl solution.6.2 Glass Beads (4 mm is recommended).6.3 Glass Stirring Rods.6.4 Tongs (Stainless stee
19、l or plastic, nonmetallic plated).7. Reagents7.1 A sodium chloride solution consisting of 5 6 0.1 % (by mass) NaCl shall be prepared using distilled or deionized waterconforming to Specification D1193 (Type 4) and ACS reagent grade NaCl solution. The 5 % NaCl solution shall be prepared noless than 1
20、6 h before beginning the corrosion testing.7.2 Concentrated HCl.7.3 Distilled or deionized water.FIG. 1 Examples of Ratings for Various Amounts of Rust or Stain (Immersion in Aqueous Solution of 5 % NaCl)B895 1628. Test Specimen8.1 Usually test parts are sintered parts, but they may also be standard
21、 transverse rupture bars as defined in Test Method B528.A minimum of ten parts/specimens shall be used for each test except for routine testing of production parts, where the use of fiveparts is acceptable. The use of ten parts/specimens is, however, recommended for evaluating new materials/processe
22、s.8.1.1 The density of the parts or specimens as well as any post sintering treatments, (that is, coining, repressing, machining, etc.)shall be stated. Parts or specimens shall be free of oil, dirt, grease and fingerprints. If they have been cleaned, the cleaning methodshall be stated. Refer to Prac
23、tices A380 and G1 for recommended cleaning practices.8.1.2 The use of tongs or gloves, or both, to prevent contamination in handling is suggested.NOTE 1Iron or low-alloy steel particles present on the surface of the sintered stainless steel parts/speciments can be revealed by placing theparts/specim
24、ens in a concentrated solution of copper sulfate, CuSO4. The dissolved copper plates out on the iron/low-alloy particles within minutes andcan be seen by using a low-magnification microscope.9. Preparation of Apparatus9.1 Soak previously used jars and glass beads in concentrated HCl for at least 12
25、h to remove rust stains; rinse with distilledor deionized water, then rinse again and allow to dry.9.1.1 Place the glass beads in the bottom of the beaker. Use a sufficient number of beads to keep the test specimen off the bottomof the jar.10. Procedure10.1 Method 1:10.1.1 Place one part or specimen
26、 per jar on top of the glass beads. Add the NaCl solution to each jar so that the volume ofsolution, in millilitres, is at least five times the mass of the specimen in grams. The distance from the surface of the part/specimento the top of the solution should be at least 25 mm. The ratio of the volum
27、e of air to the volume of solution in a jar is recommendedto be about 1:2 to 1:3. Remove air bubbles attached to the specimen surface and glass beads by swirling the solution or movingthe specimen with a glass stirring rod. Close the jars. Record the date and the time of the start of the test. Store
28、 the immersed testspecimens at a temperature of 21 to 24 C.10.1.2 Examine the parts/specimens after 12, 1, 2, 4, and 8 h 8 h and at 24 h intervals from the onset of the test. Thereafter, theinterval may be lengthened as time progresses until the first appearance of rust or stain. The corrosion life
29、of a part or specimenis the time of the previous examination, that is, the last examination taken before the observation of stain or rust. Do not includecorrosion which appears at the interface between a part/specimen and the glass beads. This is considered to be crevice corrosionand may be evaluate
30、d by Test Method G48.10.2 Method 2:10.2.1 Method 2 follows the procedure of Method 1 through 10.1.1. It continues with periodic examination as in 10.1.2, exceptthat testing continues beyond the first appearance of stain or rust. In Method 2, for each examination, the parts/specimens areranked for th
31、e degree of staining or corrosion according to the following:AThe part/specimen is free from stain or rust.BThe first sign of stain or rust appears or up to 1 % of surface is covered by stain or rust.CMore than 1 and up to 25 % of surface is covered by stain or rust.DMore than 25 % of surface is cov
32、ered by stain or rust.10.2.1.1 Examples of ratings exhibiting these conditions are shown in Fig. 1.10.2.1.2 Do not include corrosion which appears at the interface between the test specimens and the glass beads. This isconsidered to be crevice corrosion and is not the subject of this test method.As
33、a part/specimen shows increasing amounts of rust,it may become necessary to use a pair of tongs to remove it from the solution so as to distinguish between loose and adherent rust.Rinsing should not be used because loose rust may be washed off.10.2.2 Record the results of the timed observation at th
34、e intervals used. Table 1 shows a typical example of a data collectiontable.10.2.3 Plot the percent of parts/specimens having an A, B, or C class rating for suitable time intervals on a logarithmic timescale.10.2.4 Draw curves to fit the data. A typical plot is shown in Fig. 2. When plotting the dat
35、a for the “B” and “C” ratings, it isthe percentage holding a “B or better” rating and a “C or better” rating that is plotted. For example, in Table 1, a “B or better”rating is held by 100% of the specimens for up to 168 h. A “C or better” rating is held by 100% of the specimens for up to 496h.11. Re
36、port11.1 Method 1:11.1.1 Report the individual corrosion lives in hours as determined in 10.1.2 and calculate the arithmetic average. Acceptancecriteria shall be mutually agreed upon between purchaser and seller.11.1.2 Density of parts/specimens as well as any post-sintering treatments and cleaning
37、methods (if cleaned) shall be recorded.B895 16311.2 Method 2:11.2.1 Report the time when 50 % of the parts/specimens have an A, B, or C class rating.11.2.2 Photographs of tested parts, indicating the test conditions and the number of hours tested shall be provided at thecustomers request.TABLE 1 Exa
38、mple of Corrosion Rating Chart for a Set of Ten Replicate Specimens of Sintered 316L Stainless SteelASpecimen Hours submersed in 5 % aq. NaCl# 0.5 1 2 4 8 24 31 50 74 104 168 240 336 496 696 984 1368 1804 2282Specimen Hours submersed in 5 % aq. NaCl# 0.5 1 2 4 8 24 31 50 74 104 168 240 336 496 696 9
39、84 1368 1804 22821 A A A A A A A A B B B B C C C C D D D2 A A A A A A A A A A B B B B C C C D D3 A A A A A A A B B B B C C C D D D D D4 A A A A A A A A A B B B B C C C C C D5 A A A A A A A A A B B B B C C C C C C6 A A A A A A A A A B B B B C C C C C D7 A A A A A A B B B B B B C C C C C D D8 A A A A
40、A A A B B B B B C C C D D D D9 A A A A A A A A B B B B B C C C C D D10 A A A A A A A A A B B B B C C C C C D% Holding A Rating100 100 100 100 100 100 90 70 50 10 0% Holding B Rating100 90 60 10 0% Holding C Rating100 90 80 70 40 10A See Section 10.1.1 for definition of ratings.FIG. 2 Plot of Percent
41、age of Replicate Specimens with a Given Rating Versus Immersion TimeB895 16411.2.3 Density of parts or specimens as well as any post-sintering treatments and cleaning methods (if cleaned) shall berecorded.12. Precision and Bias12.1 No repeatability and reproducibility data or information on any bias
42、 inherent in these test methods are available at this time.13. Keywords13.1 corrosion; powder metallurgy (PM) parts; stainless steelSUMMARY OF CHANGESCommittee B09 has identified the location of selected changes to this standard since the last issue (B89515)that may impact the use of this standard.
43、(Approved April 1, 2016.)(1) The recommended use of ten parts for evaluating new materials/processes has been deleted from Section 8.1.B895 165SUMMARY OF CHANGESCommittee B09 has identified the location of selected changes to this standard since the last issue(B895-05(2010)B89505(2010)1) that may im
44、pact the use of this standard. (Approved October 1, 2015)(1) Added a statement on units.(2) Increased the minimum number of parts/specimens from five to ten, but indicated that five parts are acceptable for routinetesting of production parts.(3) Added a note on checking for the presence of iron or l
45、ow-alloy contamination.(4) Provided clarification in subsection 10.2.4 on the plotting of data.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determina
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