Cadmium Substitution - garteur

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GARTEUR LIMITED E.3 Results and discussion S-N curves were obtained for each of the coatings evaluated. Figure E2 gives examples of curves obtained for specimens electroplated with zinc-cobalt-iron and zinc-nickel. In these tests the specimens had a stress concentration factor (K t ) of 1.4. All the S-N curves obtained are given in reference E1 together with the individual fatigue specimen results. Data obtained from the S-N curves were used to calculate the relative effects of the different coatings on the fatigue strength of the steel. These are summarised in table E1. The fatigue strength for each of the coatings is compared with the fatigue strength for specimens, which have been abrasive blasted with alumina grit. The results obtained show that the coating causing the greatest reduction in fatigue strength is ED zinc - nickel. ED zinc-cobalt-iron was similar to ED cadmium giving a reduction of ~10% whilst the other coatings investigated resulted in a lowering in fatigue strength of about 5%. Several factors will influence the initiation of fatigue cracks on coated specimens. These include, • coating thickness • surface roughness due to grit blasting • peening effect due to grit blasting • strength of the base material • hydrogen embrittlement A detailed study has been made at NLR [E1] in order to identify the impact of these factors on the fatigue life. Metallographic sectioning has shown that there are considerable variations in the thickness of the coating within the notched region for each of the coatings. There were also found to be large differences in the surface roughness as a result of the pre-coating abrasive blasting treatment. This arises from the fact that the abrasive blasting was carried out by each of the organisations responsible for the different coating processes. Although surface roughness will influence the fatigue crack initiation, NLR's study suggests that the embedded aluminium oxide particles may act as preferred crack initiation sites. E.4 Conclusions 1. Based on constant amplitude tests the following conclusions can be drawn concerning the effects of coatings on the fatigue strength on steel. 2. By the aluminium oxide blasting treatment before the coating process the surface is roughened but also aluminium oxide particles are trapped in the surface metal. 3. Entrapped oxide particles are potential fatigue crack initiation sites. 4. The ED Zinc - nickel coating resulted in the largest reduction in fatigue strength, 25%. This was due to the hard brittle coating and the relatively large coating thickness. 5. ED zinc - cobalt - iron gave no larger reduction in fatigue strength than cadmium, ~10%. The negative effect of cadmium on fatigue strength is unexplained. Page 80 GARTEUR SM/AG17 TP128
GARTEUR LIMITED 6. For coatings ED aluminium, SermeTel 984, Delta-tone and UBMS aluminium - magnesium only a slight detrimental effect ~5% on the fatigue strength was found. E.5 References [E1] [E2] ‘t Hart W.G.J. and Boogers J.A.M., Influence on fatgiue crack initiation of environmentally friendly coatings to replace <strong>Cadmium</strong>, NLR-CR-98014 (1998) Magnusson L., Fatigue test results of SAAB work in GarteurAG17, <strong>Cadmium</strong> substitution in Aircraft, TUDL-R-4073 (1996) GARTEUR SM/AG17 TP128 Page 81
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GARTEUR LIMITED Executive summary B
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GARTEUR LIMITED nickel coatings cou
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GARTEUR LIMITED G.1 Introduction 89
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GARTEUR LIMITED The various aims of
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GARTEUR LIMITED properties and sacr
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GARTEUR LIMITED Outdoor exposure tr
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GARTEUR LIMITED 7 Discussion In the
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GARTEUR LIMITED 11 Tables Coating t
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GARTEUR LIMITED Coating Thickness
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GARTEUR LIMITED As - plated Passiva
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GARTEUR LIMITED As plated Passivate
Page 44 and 45: GARTEUR LIMITED Coating Potential r
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Page 48 and 49: GARTEUR LIMITED Properties ED Zn-Co
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Page 54 and 55: GARTEUR LIMITED A.2.4 Delta-tone/De
Page 56 and 57: GARTEUR LIMITED A.4 Tables Coating
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Page 64 and 65: GARTEUR LIMITED B.3.3 Coating Adhes
Page 66 and 67: GARTEUR LIMITED Type A Measurements
Page 68 and 69: GARTEUR LIMITED B.7 Figures Hi - Lo
Page 70 and 71: GARTEUR LIMITED ED Cadmium IVD Alum
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Page 74 and 75: GARTEUR LIMITED c) Exposure to 100%
Page 76 and 77: GARTEUR LIMITED [C7] Baldwin K.R.,
Page 78 and 79: GARTEUR LIMITED Coating rust (hours
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Page 82 and 83: GARTEUR LIMITED DBAA DERA NLR NLR B
Page 84 and 85: GARTEUR LIMITED C.7 Figures Figure
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Page 88 and 89: GARTEUR LIMITED D.6 Tables Time hou
Page 90 and 91: GARTEUR LIMITED D.7 Figures Figure
Page 92 and 93: GARTEUR LIMITED Figure D4; Current
Page 96 and 97: GARTEUR LIMITED E.6 Tables Laborato
Page 98 and 99: GARTEUR LIMITED Figure E2; S-N curv
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Page 114 and 115: GARTEUR LIMITED I.7 Tables Coating
Page 116 and 117: GARTEUR LIMITED I.8 Figures Cadmium
Page 118 and 119: GARTEUR LIMITED Cadmium coated bolt
Page 120 and 121: GARTEUR LIMITED cadmium although it
Page 122 and 123: GARTEUR LIMITED Garteur main coatin
Page 126 and 127: GARTEUR LIMITED D-28183 Bremen, GER
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