LASER TRANSFORMATION HARDENING OF FIRING NAVAL
AD-A105 498UNCLASSIFIEDF/6 20/5DCZONE CUTOUT CAMS. (U)OF FIRINGHARDENINGLASERWASHINGTONLOWRY COMMANDR TPNL
" VNAVSEA REPORT NO. S555-79r24JUNE 1981LASER TRANSFORMATION HARDENINGOF FIRING ZONE CUTOUT CAMSFINAL REPORTAPROJECT OF THEMANUFACTURING TECHNOLOGY PROGRAMNAVAL SEA SYSTEMS COMMANDDTI C- E.CTEf.OCT 1 5 1980F1byAROBERT W. LOWRYApproved for public release; distribution unlimited.NAVAL SURFACE WEAPONS CENTERDAHLGREN, VIRGINIA 22448SILVER SPRING, MARYLAND 20910"Al
NAVSEA Report No. S555-79June 19814LASER TRANSFORMATION HARDENINGOF FIRING ZONE CUTOUT CAMSFINAL REPORTA Project of TheManufacturing Technology ProgjramNaval Sea Systems CommandbyRobert W. LowryNAVAL SURFACE WEAPONS CENTERSilver Spring, Maryland22448Dahlgren, Virginia20910
UNCLASSIFIEDCLASSIFICATION OF THIS PAGE (When Data Entered)REPORT DOCUMENTfATION PAGEREADINSTRUCTIONSBEFORE COMPLETING FORMNSA94.*.2. GOVT ACCESSION NO. 3.RECS.TYPTITLE (and Subtitle)e'SCATALOG NUMBERFfitPORT 6 PERIOD COVEREDLASER TRANSFORMATION IARDENING OF FIRING ZONEFinal04CUTOUT CAMS.PERFORMING ORG. REPO7.-6.AUTHOR(i)Roer9.S. CONTRACT OR GRANT NUMBER(*)W./InwryPERFORMING ORGANIZATION NAME AND ADDRESSNaval Surface Weapons Center10.(G53)Dahlgren, VA 2244811.PROGRAM ELEMENT, PROJECT, TASKAREA & WORK UNIT NUMBERSDNS 0055CONTRCLLING OFFICE NAME AND ADDRESSINaval Sea Systems Command (05R),1113.Washington, DC 2036214.NUMBERMONITORING AGENCY NAME & ADDRESSQ[f different from Controlling Office)JunbSelNUMBER OF4343IS.PIAGESSECURITY CLASS. (of this DISTRIBUTIONSTATEMENT (of this Report)Approved for public release; distribution unlimited.17.DISTRIBUTION STATEMENT (of the abstract entered in Block 20, if different from Report)IS.SUPPLEMENTARYNOTES19. KEY WORDS (Continue on reverse side if neceseary nd identity by block number)Laser Transformation Hardening Cams20.ABSTRACT (Continue on reveres side If necessary and Identify by block number)This manufacturing technology (MT) project developed techniques to uselaser transformation hardening to replace cyanide salt bath nitriding to caseharden firing zone cutout cams for the Mk 10 Guided Missile Launcher System(GMLS). These cams, machined of 4340 steel, satisfactorily meet the manufacturing requirements of a case depth of 0.010-0.020 in. and a hardness ofR C 55-67, with minimal distortion, after undergoing laser hardening. Thelaser transformation, utilizing a beam oscillator and numerical controlDDDOANMt31473EDITION OF I NOV 65 1S OBSOLETEJAN731473S/N 0102-LF-014-6601UNCLASSIFIEDU.ILUNIT"Y CLASSIFICATION OF THIS PAGE (lIten Date Bnle ed)/
I4UNCLASSIFIEDSECURITY CLASSIFICATION OF THIS PAGE (When Dats Entered)20.ABSTRACT (Continued)stepping procedures to minimize heat buildup, produces a very fine martensiticstructure that is hard, typically R C 62.This hardness is reduced somewhatin the beam overlap regions, but this factor is compensated for by cam preheat treatment and sufficient overlap of laser beam passes. The cost of laserhardening is estimated at less than 10 percent of the cost of CATION OFrTMIS PAGE(Whon Data Entered)
FOREWORDThe project reported herein was sponsored by Naval Sea Systems Command,Manufacturing Technology Office (NAVSEA 05R2).The work was funded under Project 4038-79, DNS 555. The purpose of the undertaking was to reduce the costof surface hardening by developing laser transformation hardening as a replacement for the nitriding process. This project was demonstrated on the firingzone cutout cam of the Mk 10 Guided Missile Launching System (GMLS), but opensthe door for laser treating a host of other naval surface weapons andcomponents with the potential for additional cost savings and technologicaladvantages.The author wishes to acknowledge the following persons for their technicalassistance: Robert Retter and Emmett Staples for metallographic analysis andEarl Baird for background information and hardware assistance.This report has been reviewed and approved by Jerry Hall, Head, MaterialsScience Branch; Dr. John Thompson, Manufacturing Technology Program Manager;and David Malyevac, Head, Survivability and Applied Sciences Division.Red by:Assistant Head for Weapons SystemsWeapons Systems DepartmentIv
EXECUTIVE SUMMARYThis manufacturing technology (MT) project developed techniques to uselaser transformation hardening to replace cyanide salt bath nitriding to caseharden firing zone cutout cams for the Mk 10 Guided Missile Launcher System(GMLS). These cams, machined of 4340 steel, satisfactorily meet the manufacturing requirements of a case depth of 0.010-0.020 in. and a hardness of Rc 55-67,with minimal distortion, after undergoing laser hardening.The laser transformation, utilizing a beam oscillator and numerical control stepping proceduresto minimize heat buildup, produces a very fine martensitic structure that is hard,typically Rc 62.This hardness is reduced somewhat in the beam overlap regions,but this factor is compensated for by cam preheat treatment and sufficient overlap of laser beam passes.The cost of laser hardening is estimated at less than10 percent of the cost of cyanide nitriding.vii
CTIVE.1BACKGROUND.1APPROACH.4MATERIALS.5BAS ICS OF LASER HEAT TREATMENT.6EQUIPMENT AND PROCEDURE DEVELOPMENT.9RESULTS.11SUMMARY.11METALLURGICAL ANALYSIS.12Hardness.12Metallography.14TOLERANCE CONTROL.18WEAR TEST.22CORROSION TEST.24ADVANTAGES OF LASER PROCESSING.25Cost Analysis.25Applicability of Laser Processing to Other ENCES.29DISTRIBUTIONviii.27
LIST OF Page. .Photograph of Mk 10 Firing Zone Cutout Cam .Photograph of USS BELKNAP (CG 26) Showing Mk 10 TerrierLauncher (Encircled) .Illustration of Missile Being Fired to Clear Ship.Superstructure (DDG 37 Class) .Illustration of Cam Contour .Typical Firing Cutout Zone .Schematic Illustration of Regions of Laser Power Density.and Interaction Time .General Concept of Laser Heat Treating by the Use of.oscillating Laser Beam .Laser Heat-Treating Patterns . .Laser Beam Step Pattern . .Hardness Profile, 4340 Steel .Laser-Treated Cam (Defocused Beam, 0.100-in. Passes) . .Laser-Treated Cam (Oscillated Beam, 0.300-in. Passes) . . .Laser-Treated Cam Cross Section (Multiple Oscillated. .Passes, 4340 Steel) .Laser-Treated Cam Cross Section (Multiple Passes,Defocused Beam, No Oscillation, 4340 Steel) .Laser-Transformation-Hardened Cam (Approximately 0.017-in. .Penetration, 4340 Steel) .Laser-Treated Cam Bevel (Approximately 0.020-in. .Penetration) .Overlap of Two Laser Passes Using Beam Oscillator . .Laser-Transformed 4340 Steel Cam (Microstructure is FineMartensite) . .Cam Follower Used on the Mk 10 Type Firing Cutout Cam . . .Photograph of Wear Test Setup Showing Laser-Treated Cam. .(Right) and Nitrided Cam (Left).Photograph of Wear Test Setup Showing Follower for the.Laser-Treated Cam.Cam Sections After 48-Hour Salt-Spray TestCam Sections After 48-Hour Salt-Spray Test (Reverse.of Figure 22) .ix12233778101213141515161617172222232424
LIST OF TABLES4TablePage234Typical Chemical Compositions (Percent Weight) of Cam5. .Nitride Versus Laser Treatment (Batch of Four Cams). . 10. 19Cam Tolerance Chart . . 21Cam Tolerance Summary . .5Economic Analysis . .14Steels.x.27
INTRODUCTIONOBJECTIVEThe technical objective of this project was to develop production methodsfor laser processing as an alternative to nitriding as a means of surface hardening firing zone cutout cams for the Mk 10 Guided Missile Launcher SystemA coincident objective was to reduce the cost of the hardening pro(GMLS).cess, while meeting cam surface requirements. The surface requirements are acase depth of 0.010-0.020 in. and a hardness of Rc 55-67 with minimal distortion.BACKGROUNDThe Naval Surface Weapons Center (NSWC) is currently the design agent forThese items are usedthe Mk 10 GMLS firing zone cutout cam (see Figure 1).aboard ship to confine launcher azimuth and elevation angles in order to prevent firing the missile toward ship structures. Figures 2-5 help illustratethe cam function. Figure 2 is a photograph of the USS BELKNAP (CG 26), whichhas a Terrier missile launcher (encircled) that uses the Mk 10 firing zonecutout cam. Figure 3, a schematic of a DDG 37 class ship, shows a missilebeing launched to avoid the ship's superstructure. Figure 4 provides an example of cam contour, while Figure 5 provides a schematic of a typical firingcutout zone. The contour of the cam corresponds to the nonfiring zone profilethat is configured to the layout of the ship superstructure. A cam follower(contact pin), when in contact with the cam, tells the launcher not to fire.Figure 1. Photograph of Mk 10 Firing Zone Cutout Cam
FT--kFigure 2. Photograph of USS BELKNAP (CG 26) showing Mk 10 Ter rier Launcher (Encircled)ANHTENN4ASSupeRtrutuEShip ADRNT00,HEMISPHERfOALSCANRAD ARUNIT(DG lSEA)CADR NT2N
2 156 R TO VORTEX OFCUTTER FORALL DIM OFCAM CONTOUR(j OFCAM.031 .010 FORALLDIM OF CAM CONTOURS3AP05396EDGES90, 134 SHARPEDGESz-z.0100314 1 R TYPICAl.k-i031OFCUTTER PERDIMENSION OF CAMDEVELOPMENTOFCTR61SEEDETAIL29- .010jOF CUTTER1.034DETAIL Z-Z2320ZERO POSITIONALIGNMENT HOLEFigure 4.Illustration of Cam Contour6040 -a /NON-FIRING ZONE/03001033003060IO0TRAIN ANGLE (dog)Figure 5.Schematic Illustration of Typical Firing Cutout Zone3
The final step in cam manufacture is case hardening. The required quickturnaround (to meet fleet/ship requirements and schedules) is presently beingperformed by a cyanide salt bath nitriding processing of nitralloy steel cams.This process produces a 55-60 Rc hardness and a case depth of 0.010 in. Therequirements are a 55-67 Rc hardness and a case depth of 0.010-0.020 in. Oneset of two cams has been hardened approximately every 60 days. This method(based on 12 cams/year) costs over 18K per year, which includes the high costof disposing of toxic cyanide salt waste ( 6K/yr) and the total energy consumption of the 60-kW salt bath ( 3K/yr) for this energy-intensive operation.These costs are based upon historical data from the 1970s. On a 12 cam/yearbasis, today's costs would be even higher.A more cost-effective and less energy-consuming method for surface hardening these parts is laser hardening, which has recently been proven as a pracmanufacture of automobile engine camshafts, gears,tical industrial tool 1 in theand bearing surfaces. ,2,3 The laser provides very low operating and maintenance costs compared to salt bath nitriding. Specifically, the laser in thisapplication uses approximately 0.29 percent of the electrical energy of thecyanide salt bath. Furthermore, thicker case depths than those being obtainedby nitriding are possible by laser hardening.APPROACHOriginally, it was planned to use the 20-kW laser at the Naval ResearchLaboratory (NRL) to conduct the surface transformation hardening studies.However, after conducting a preliminary study on nitralloy steel using the NRLlaser, it was learned that, because of commitment to other studies, turnaroundtime and scheduling would be a significant problem. Therefore, it was decidedto use a laser from a private contractor. One advantage of this decision willbe an early involvement of industry in the manufacturing process. It was alsodecided, after discussion with Laser Applications Inc., Baltimore, Maryland,that a smaller laser would be sufficient to do the job and that they couldsatisfy the Navy's cost and turnaround time requirements.4time,Studies were then initiated using Laser Application's 1.25-kW laser toperform the surface transformation hardening of cams. These studies weredirected at determining the effects of laser power (beam intensity), dwellcam rotation speed, beam width, and beam oscillation on cam surface hardness and case depth. Hardness measurements were made and samples metallographically examined to assure that the cam cross sections are metallurgically soundand wear resistant. Wear tests, corrosion tests, and tolerance studies wereconducted to obtain backup data to assure cam performance, reliability, andlaser process repeatability.It is anticipated that the laser transformation hardening production method will be implemented following completion of this manufacturing technologyprogram. Laser equipment at Laser Applications, Inc., may be used. It isanticipated that 12 cams per year will be manufactured for approximately eightmore years.4. . -,,. Ild. . . . i iii . . .i I. . .
MATERIALSFour steels were considered suitable for laser transformation hardening tothe desired hardness: nitralloy 135 modified, 4340, 1045, and 11L41 steels.The chemical compositions of these steels are shown in Table 1. The nitralloy135 modified steel was examined early in the program because of its immediateavailability as the current nitriding steel on stock. This material was foundto be unsuitable because of surface eruptions and roughness upon laser impingement. AISI 4340 steel was selected because of hardenability, contractor experience, and surface smoothness after laser transformation hardening. The1045 steel was selected as a low-cost alternative to 4340, and 11L41 wasconsidered as a relatively low-cost material with good machinability.Table 1.Typical Chemical Compositions (Percent Weight) of Cam mMolybdenumNickelPhosphorusSulphurLeadNitralloy135 Mod0.410.550.301.601.000.350.04 max.0.05 max.43400.400.700.300.800.251.850.04 max.0.05 max.AISI104511L410.450.750.220.411.500.04 max.0.05 max.0.04 max.0.08-0.130.25The two primary steels (4340 and 1045) were laser treated in both the asreceived (hot rolled) and the heat-treated (called "preheat treatment"throughout the text) conditions. Preheat treatment is required to obtainproper hardness for the cam hobs. In addition, preheat treatment helps reducethe effect of tempering, which occurs at overlapping laser beam passes, andhelps reduce warpage during laser heat treatment.Important material properties for laser surface hardening are density,specific heat, thermal conductivity, and thermal diffusivity. Approximateproperty values for the steels tested are as follows:. Density 7.87 g/cc. Specific Heat0.11 cal/g. c5
. Thermal Conductivity 9.7 x 10 *2cal/cm-s. cThermal Diffusivity* 0.21 cm 2 /secThese values determine depth of penetration and will not be discussed in detailhere but are covered in the literature."BASICS OF LASER HEAT TREATMENTLASER is an acronym standing for Light Amplification by Stimulated Emisionof Radiation. Important laser properties are listed below.1. Monochromaticity. Light energy from a laser is produced at a muchnarrower bandwidth and at a considerably higher intensity than energy producedby other light sources.2. Coherence. Waveforms are regular and predictable with the samefrequency, phase, amplitude, and direction.3. Divergence. Waveforms are very parallel and, thus, energy remainsintense over long distances.4. Intensity. Outout from well-collimated laser light can be focused toa very small spot with high energy concentration.Regions of laser operations with regard to power density and interactiontime is illustrated in Figure 6. The power required for laser hardening (heattreating) is in the region of 103 - 105 W/cm 2 . An interaction time on theorder of 10- i - 10-2 sec is necessary.The general concept of laser heat treating by the use of oscillating laserbeams is illustrated in Figure 7. In this procedure, the laser beam isoscillated back and forth as the material is rotated or translated to provide awider area of heat treatment. The material is heated very quickly above thetransformation temperature (of a hardenable steel or alloy) and self-quenchesrapidly to produce a largely martensitic (hard) microstructure.* Thermal diffusivity is thermal conductivity x heatingis for a composition close to that of 4340 steel.rate.The value shownI
10-DRLLNPLASMA IGNITIONDi*SURFACE VAPORIZATION A'MELT ONSET10-6I10-710-510-40-10-210-1100INTERACTION TIME Isec)rlFigure6.Regions of Laser Power Density and Interaction Time*TmLASERIIET UVAAVM.M,.0TIMEFigure 7.by-*1976,FGeneral Concept of Laser Heat Treatingthe Use of oscillating Laser Beam*with permission,*Reprinted,pp.25-28),-MiltonS.from Electro-Optical Systems Design (Nov.Kiver Publishers, Inc., Chicago, Il.7
Laser heat-treating patterns are shown in Figure 8 for (a) defocused beam,single pass, (b) defocused beam, overlapping passes, and (c) oscillating beam,single pass. It should be noted that there is a small over-tempered zone of afew thousandths of an inch wide at the periphery of a pass and at the interfacebetween two passes. These overlapping areas will be discussed in more detailwith reference to the cams in a later section.SURFACE. ::.DEPTHa. DEFOCUSEDBEAM, SINGLEPASSOVER-TEMPERED ZONEHARDENEDAREASURFACE13. kDEFOCUSED BEAM,--i1-,-"OVERLAPPINGPASSESPASSPASSNO. 1NO. 2WIDTHSURFACE14" ::: :- HARDENEDDEPTHDEPTHc. OSCILLATING BEAM,SINGLE PASSOVER-TEMPERED ZONEAREAFigure 8.Laser Heat-Treating Patterns*.11 Reprinted, with permission, from Flectro-Optical Systems Design (Nov.1976, pp. 25-28),Milton S. Kiver Publishers, Inc., Chicago, Il.8
--azEQUIPMENT AND PROCEDURE DEVELOPMENTThree basic pieces of equipment were used in conjunction withand fixtures required to manipulate the cam during heat treatment:the tooling(1) a 1.25-kWCO 2 laser (10.6-pm wavelength) and (2) a laser beam oscillator (Model 447),both manufactured by Photon Sources, Inc.; and (3) a computerized numericalcontrol (CNC) unit produced by Aerotech, Inc. The laser, of course, is theheat source, the oscillator provides rastering of the beam, while the CNC unitprovides programmable automatic rotation and stepping of the cam.Three different methods were tried in the development of the laser heattreatment of the cam:1.Defocused beam with manual tilt2.Focused beam with oscillation3.Focused beam with oscillation; cam stepped with the CNC unit(450)for bevelsThe first method did not employ the laser beam oscillator and required a 45*manual tilt of the cam in order to harden the beveled surface of the cam.Although the heat treatment/hardening results were acceptable using this method, the manual tilt required time and precision in alignment of the laser beamon the beveled surface.Also, without oscillation, more laser passes wererequired to heat treat the cam outer surface than with the wider laser passesobtained with the oscillated beam (methods two and three).The width of theoscillated passes was approximately 0.25 in. compared to 0.10 in. for the nonoscillated beam. The use of oscillation in the second method eliminated thetilt and decreased the operation time.Use of an aluminum insert heat sinkwith thermal coat was required to reduce heat buildup and control distortion inthe relatively thin-walled (approx. 0.33 in.) cam. The third and final methodemployed stepping the cam with the CNC unit to further control heat input distortion especially on the highest lip of the cam. This required programming ofthe CNC unit.Stepping of the cam is illustrated in Figure 9, a schematic ofthe cam showing the laser passes--lined off and numbered in order of the stepping sequence.A comparison of the steps in nitride versus laser treatment for a batch offour cams is provided in Table 2. The time-consuming factors for the nitrideprocess are the startup and shutdown of the salt bath, disposal of cyanide saltwastes, and the actual 24-hour nitride heat treatment itself.The most timeconsuming task unique to the laser process is the preparation and checkout ofthe CNC computer program (2 hours).The total time for the nitride process istwo weeks (including startup and shutdown) while that for the laser operationtotals 10 hours (including transportation to laser).The laser surface treatment requires about 15 minutes to conduct per cam, which includes 5-7 minutesdwell time for the laser.Therefore, the actual run time for the laser is onlyThe salt bath8-10 minutes per cam (32-40 minutes per batch of four cams).operates at 60 kW while the laser operates at 1 kW. Therefore, the nitrideprocess uses approximately 345 times the kilowatt-hours compared to the laser.9
3.199211691.938417171.593113191I2590 40isJ3120 50 470[ 310'9.seLaeTerClean cams.Preheat treat cam. Mask off hobs. Prepare cyanide salt bath* Nitride (24 hr/batch of four cams)* clean cams (shot peen).Check case depthCheck case hardness. Shut down salt bath. Cyanide salt waste disposal. Gage cams*1j15Fiur9. Lae BemSeFigurde20 941021in,. 095In.10149050'2100 10'aten(eunetpPttrqecet- Clean cams*Preheat treat cam* Check out parameters(power, mode, etc.)Prepare and check computer program9 Insert heat sink into cam* Spray graphite coating- Set beam oscillator parameters9 Laser surface treatment (-15 min./cam)* Clean cam (wipe off)* Check hardnessa Check case depth9Gage cams*Total time 2 weeksTotal time 10 hours10
*It should be noted in Table 2 that a carbon spray coating was applied tothe cam surfacze to provide heat coupling for the laser energy to the steel.Otherwise inost of the light (approximately 90 percent) would be reflected andnot absorbed.Laser characteristics and parameters are listed below.* Power:1000 W- Standoff:8.75 in. Spot size:-* Focal length:0.070 in.7.5 in.4- Rotation rate:30 in./min.o Oscillator rate:100 Hz, 2 V, sine wave* Scan length:0.250 in.* CNC program:17-21 steps Run time:15 min. (approx.)Included in this list are the oscillator parameters. These parameters appliedto the cams produce the results described in the next section. These are thefinal process parameters after process development. These parameters werevaried over a considerable range during development.RESULTSSUMMARYA summary of the results is provided below. Hardness:Profile 62 Rc; Overlap 51 Rc (very narrow band). Depth:Profile 0.015-0.017 in.; Overlap 0.009-0.010 in.(Can get 0.025 to 0.030warpage and melt). Tolerance:in. with more heat but withWithin 4 min. trainWithin 0.001 in. elevation9 Microstructure: Highly refined martensite* Wear:-0.0001in.11Ah-Acceptable
The results show that the requirements of RC 55-67 and 0.010-0.020 in. depthof penetration with minimal distortion can be met. These values represent thebest results obtained to date. A larger data base is required to determine therepeatability of tolerance control. This information will be collected onThe microstructurefleet cams as they are processed by laser heat treatment.is basically a highly refined martensitic microstructure yielding a hard yetThe actual weartough microstructure suitable for good wear resistance.resistance compares favorably with that of nitrided cams.Problems encountered in laser heat treatment of cams are (1) somewhatreduced hardness in the narrow overlap bands between laser passes, (2) potential for heat buildup causing tolerance distortion in outer members (lips), and(3) rounding of bevel edges/corners caused by incipient melt, which providesgaging difficulties. Each of these problems was addressed in this project.Tolerance distortion is the most significant problem and will be discussed indetail.METALLURGICAL ANALYSISHardnessHardness results for cams made of 4340 and 1045 steels are compared inFigure 10. Both steels hardened to nearly the same peak hardness (Rc 62) butthe 4340 steel hardened more consistently to a greater depth.AISI 4340 steelis a deep-hardening steel and provides a smooth laser-hardened surface.RCHARDNESS --SURFACE3020405055 60I6770I0.005*10.010---i 1045STEELoo154340 STEEL0.0200.0251-20 RCFigure 10.4IPOWER 1000 WSPEED 30 IPMMODE TEMdxI (DOUGHNUT)SPOTSIZE 0.070 in.S WIDTH 0.25 in.FREQ 100 Hz41RCHardness Profile, 4340 Steel12
Initially, one problem encountered in obtaining uniform surface hardnesswas the overtempered zone or softening that occurs at laser beam interfaces ofoverlapping passes. These soft zones are very narrow in width (on the order ofa few thousandths of an inch wide or a few hundredths of a millimeter).Thehardness in these zones varies from 45-54 Rc for the 4340 steel, which wasprehardened to 41 Rc. The 1045 steel was not prehardened in this particularcase and the overlap hardness dropped off to the base hardness of Rc 20.Inanother case, the 1045 steel was prehardened to about 35-38 Rc which didimprove the soft band hardness somewhat but not to the level of 4340 steel.Another problem with 1045 steel was poor machinability, both in the hot-rolled(as-received) condition and the hardened condition. The 4340 steel was botheasier to machine and to laser harden from a penetration and surface-smoothnessstandpoint. As a result ot prehardening and improvements in carbon spray coating, combined with proper laser pass overlapping, the soft bands have beennearly eliminated. They are very difficult to locate with a hardness tester.Photographs of laser-hardened cams are shown in Figures 11 and 72. Thethin lines (indicated by arrows) are the overlap zones between laser passes.Figure 11 shows 0.100-in.-wide (2.54 mm) laser passes without oscillation andFigure 12 shows the wider 0.300-in.-wide (6.4 mm) laser passes with beam oscillation.OVERLAP ZONEHARDNESS RC 45-54Figure 11.Laser-Treated Cam (Defocused Beam, 0.100-in. Passes)13
OVERLAP ZONEHARDNESS RC 45-544Figure 12.Laser-Treated Cam (oscillated Beam, 0.300-in. Passes)MetallographyMacrographs of cam sections showing laser-hardened zones produced with andwithout laser beam oscillation are shown in Figures 13 and 14, respectively.Note the excellent coverage of the bevel (right side of macrograph) in Figure 13.The oscillated beams provide wider (plateau-like) and, therefore, fewer passesthan the bell-shaped nonoscillated beam. Micrographs are provided in Figures 1518 and show details of the laser-transformed microstructure. The white zonesin Figures 15-17 are the laser-transformed microstructures while the dark zonesare the parent metal microstructures. Figure 15 shows a 0.017-in. (0.43 mm)laser-hardened zone on a straight circumferential surface of a 4340 steel cam.Figure 16 shows laser penetration on the corner of a cam at the bevel. Laserpenetration at cam corners is extremely good because of the cam geometry. Itshould be mentioned here that the cam bevels, edges, and corners are veryimportant from a hardness standpoint because of cam follower impingement onthem. Figure 17 shows overlap between two laser passes providing good lasercoverage at the interface. This interface will possess adequate hardnessbecause of the overlap and depth attained by the laser.14
A closeup view of the laser-transformed microstructure is shown in Figure 18.This structure is a very fine tempered martensite with some bainite. Thismicrostructure is very hard and should be durable because of its toughness.i I iI I I I i3.2 3 4 ,5 6 7 8 93AVIIHOL,MASS.U.S.A."2 3 4 5 6 7Figure 13.849Laser-Treated Cam Cross Section (MultipleOscillated Passes, 4340 Steel)ATHOL.AI.ASS. ,,Figure 14. Laser-Treated Cam Cross Section (Multiple Passes,Defocused Beam, No Oscillation, 4340 Steel)15
Figure 15.Laser-Transformation-Hardened Cam (Approximately0.017-in. Penetration, 4340 Steel)Figure 16.Laser-Treated Cam Bpvel (Approximately0.020-in. Penetration)1Ib
50XFigure 17.Overlap or Two Laser Passes Using Beam Oscillator800XLa,;er-Transtormed 4340 Steel CamFiquire 183.(Mirrostructure is Fine Martensite)17
TOLERANCE CONTROLOne of the problems encountered in laser treating the Mk 10 cams was tolerance distortion caused by heat buildup. This occurred primarily on the highlip of the cam. Also, corners and edges, especially at the bevels and thealignment hole, were rounded because of the high heat intensity, causing difficulties in gaging the necessary dimensions. The distortion occurred as heatgradually built up in the relatively thin cam body as the number of laser passes increased. Heat buildup can more readily cause a problem in the highestlip of the cam where there is only a small amount of mass to dissipate heat.Rounding of corners and bevel edges, caused by incipient melting, occurredbecause of the effect of laser heat intensity being increased by the edge geometry.The heat buildup problem in the cam body and high lip was resolved byproviding the appropriate dwell time between passes and stepping the laser todistribute the heat from one location to another. Except for the first fewIt waspasses, which were made without dwells, the dwell time was 30 sec.especially important to keep from concentrating heat in the high lip. Thesecond problem, incipient melt, was handled by wiping off the thermal spraycoating of carbon precisely o
cam contour (j of cam.031 .010 for all s3ap05396 dim of cam contour edges 61 ofctr 90, 1 see detail29 34 z-z sharp edges _ 4 1 031 .010 r typical.k of cutter per -i031 - .010 dimension of cam development jof cutter 1.034 detail z-z 232 0 zero position alignment hole figure 4. illustration of c
Case Study: Laser Hardening By Markus A. Ruetering The hardening of materials by laser is a specialized and fast-growing field, as it offers improved wear resistance, . the industry — e.g., oven hardening, flame hardening, and induction hardening — mill - ing, shaping, and grinding are necessary after hardening. Hence, the necessary material
Thermal Methods of Hardening by Comparison FLAME HARDENING METHOD ADVANTAGES DISADVANTAGES 0,4% C 0,7% (Steel casting) Large parts Wall thickness 15 mm Localized hardening of functional surfaces Low technical complexity Poor reproducibility; Ledeburite hardening at high carbon content INDUCTIVE HARDENING LASER HARDENING Focus on Steel .
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this study is IPv6-only hardening. Any other type of hardening (e.g. DC hardening, web server hardening, database hardening, etc.) are beyond the scope of this study. The services provided by the IPv6-capable servers do not rely on any IPv6 Extension header, or on any multicast traffic.
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The three important surface hardening methods from left to right are case hardening, nitriding, and induction-flame-hardening respectively . 4 13FTM22 Surface hardening is carried out at treating temperatures 50 C - 100 C above the material-specific hardening temperature. The heating can be done by flame, induction, laser- or electron beam.
Laser treatment parameters for the Laser RAP sites included an average laser spot size of 4.1mm (range: 4-8mm). The average laser fluence used was 5.22J/cm2 (range 1.5-8.3J/cm2). At the Laser‐Only treated sites, a single laser pass was administered using a laser spot size of 4mm at an average laser fluence of 3.9J/cm2(range: 3.-4.6J/cm2).
FLAME- /INDUCTION HARDENING. Temperature: 850-870 C (1560-1600 F). Cooling: freely in air. Surface hardness: 54-56 HRC. Hardening depth: 41 HRC at a depth of 3.5- 4 mm (0.14-0.16 inch) when flame hardening. Can be increased when induction hardening depend - ing on the coil and the power input. Flame or induction hardening can be done
