CHEMICAL SURFACE TREATMENT. OF TITANIUM to. WATERTOWN ARSENAL
. October 30, 195 3 by. H. A. Pray, P. D. Miller, and Richard A. Jefferys.
CHEMICAL SURFACE TREATMENT OF TITANIUM to
October 30, 1953
CHEMICAL SURFACE TREATMENT OF TITANIUM to WATERTOWN ARSENAL
H. A. Pray, P. D. Miller, and Richard A. Jefferys
Contract No. DA-33-0 19-ORD-2 1 5 W.A.L. File No. 401/45-33 O.O. Project No. TB4-15 D, A Project No. 593-08-Oil
BATTELLE MEMORIAL INSTITUTE 505 King Avenue Columbus 1, Ohio
No. of Copies
Department of the Army Office, Chief of Ordnance The Pentagon Washington f Cot
Sent To Director Naval Research Laboratory Anacostia Station Washington, D. C.
Commanding Officer Rock Island Arsenal Rock Island, Illinois
Commanding Officer Springfield Armory Springfield, Massachusetts
Chief Office of Naval Research Navy Department Washington, D. C.
Commanding Officer Watervliet Arsenal Watervliet, New York
Commanding General Air Materiel Command Wright-Patterson Air Force Base Ohio Attn: Production Resources MCPB & Flight Research Lab.
Commanding Officer Office of Ordnance Research U. S. Army, Duke University 2127 Myrtle Drive Durham, North Carolina Chief Bureau of Aeronautics Navy Department Washington 25, D. C. Chief Bureau of Ordnance Navy Department Washington 25, D. C. Chief Bureau of Ships Navy Department Washington 2 5, D. C. Attn: Code 324 Chief Naval Experimental Station Navy Department Annapolis, Maryland Commanding Officer Naval Proving Ground Dahlgran, Virginia Attn: A & P Lab.
I' om mande r Air Materiel Command Wr ight- Patter son Air Force Base Ohio
Titanium Section Material Lab. WCR
Director U. S. Department of Interior Bureau ot Mines Washington, D. C.
Chief Bureau oi Mines Eastern Research Stati >n College Park; Maryland
National Advisory Committee for Aeronautics 1^00 New Hampshire Avenue Washington, D. C. Office of the Chief oi Engineers Department of the Army Washington 25, D. C. Attn: Eng. Res. & Dev. Div. , Military Oper.
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U. S. Atomic Energy Commission Technical Information Service P. O. Box 62 Oak Ridge, Tennessee Attn: Chief, Library Branch
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District Chief Cleveland Ordnance District 1367 East Sixth Street Cleveland 14, Ohio Sam Tour and Company, Inc. 44 Trinity Place New York 6, New York Armour Research Foundation Technology Center Chicago 1 b, Illinois Attn: Mr. R. W. Hanzel Dr. H. T. Francis Carnegie Institute of Tech. Schenley Park Pittsburgh 1 3, Pennsylvania Attn: Prof. D. W. Ver Planck Commanding Officer Watertown Arsenal Watertown 11, Massachusetts Attn: Technical Repre sentative Commanding Officer Watertown Arsenal Watertown 11, Massachusetts Attn: Laboratory Department of Army Office, Chief of Ordnance The Pentagon Washington 25, D. C. Attn: ORDGU-SE
N S T I T U T E
Contractor: Battelle Memorial Institute Agency: Office, Chief of Ordnance Ordnance District: Contract Number:
Cleveland DA-3 3-0 19-ORD-Z 1 5, W.A.L. File No. 401/45-33
P.O. Project Number: D/A Project Number:
Title: Chemical Surface Treatment of Titanium Authors:
H. A. Pray, P. D. Miller, and Richard A. Jefferys
Object: To initiate development and operation of various chemical and electrochemical surface treatments of titanium and us alloys, with emphasis upon practical application. Summary: This is the final report under Contract No. DA-3 3-0 19-ORD-Z 1 5 on the "Chemical Surface Treatment of Titanium". It contains a discussion of the research conducted during the contract period from May 23, 1951, to October 30. 1953. Tne investigation of surface treatments for titanium has resulted in the development of two types of baths that produce adherent, continuous coatings on titanium and its alloys. The first type is represented by a 5 per cent sodium hydroxide anodic bath and the second by the fluoridephosphate and the fluoride-borate immersion baths. Considerable attention has been given to the evaluation of these coatings. As a consequence, it has been shown that they are quite useful in several fields. For example, the coatings minimize greatly the severe galling tendency of titanium. Extensive laboratory tests have shown that they are useful in wire or tube drawing. By comparison with present commercial methods for drawing titanium, such coatings show important possibilities in the future fabrication and use of the metal. It was found that certain treatments produced coatings that provided good service for various types of reciprocating and rotary wear. Samples ran continuously for over a month in reciprocating wear at 2500 psi and for several hundred hours in more severe rotary wear. These treatments involved coating the titanium in an immersion bath to produce an adherent, BATTELLE
continuous crystalline coating, followed by (1) a heat treatment in air at about 800 F for 3 hours or by (2) application of a MoS^-Epon resin mixture. It is felt that these processes are of considerable potential usefulness because wear resistance can be produced at temperatures below those at which any phase transformation of the metal can occur. The wear resistance is comparable to that for carbonized or nitrided surfaces which require high-temperature treatments, resulting in damage to the core properties. Paint-adhesion tests have shown value for the surface conversion coatings in paint applications on titanium articles.
.3 .3 3 [ 3 13
TABLE OF CONTENTS Pag>
INTRODUCTION EXPERIMENTAL WORK
. 2 I
Anodic -Coating Development Chemical -Co.ittng Development I reatment of Coatings Heat Treatment Lub ric ation Evaluation and Application High-Pre ssu re Wear Wire-Drawing Tests Reciprocating Wear . Rotary Wear PsTnl Adhesion
9 1 5 I i 1 5 1 1 21
FINAL REPORT on CHEMICAL SURFACE TREATMENT OF TITANIUM to WATERTOWN ARSENAL
from BATTELLE MEMORIAL INSTITUTE by H. A. Pray, P. D. Miller, and Richard A. Jefferys October 30,
The development of surface coatings and conversion films has increased the usefulness of many metals. For example, aluminum, magnesium, and steel have found extended application because of useful Miriui e properties produced by chemical treatments. Wear resistance, i-.i-.i- of forming and drawing, corrosion resistance, paint adhesion, and decorative effects have been improved. While the corrosion resistance of titanium exceeds that of most metals, its use is limited by the tendency to :.>':'. .md seize when placed in loaded contact with another metal. fin- research program established under trie subject contract included: (1) a basic study of chemical and electrochemical reactions of titanium, and [2) the development of practical treatments to minimize or alleviate the problems encountered in titanium applications. Such applications might be wear, cold drawing and forming, resistance to oxidation, and paint adhesion.
Anodic-Coating Development TABLE 1. An extensive investigation of anodic treatments on titanium was made. In general, titanium reacts anodically to form thin, colored films of little value. However, a few aqueous baths were found which would produce fairly thick anodic coatings. Table 1 shows the compositions and operating conditions of the most promising anodic baths.
Bd'h No. I'M
Of the many anodic baths studied, the 5 per cent NaOH bath gave the best coating. The coating was sparkling gray and adherent, and possessed a smooth slippery surface. Evaluation tests of this coating are discussed later.
The pretreatment given to all specimens before anodizing was a hot sodium metasilicate degrease followed by a water rinse and an acid pickle in a solution of:
lUOg NaOH I900g HjO ^14 NaAlO^ -_• N.iH^POj- H^O
This solution removed any scale or oxide film that might be present. The composition and the nature of the titanium surface were found to influence the formation of the anodic coating. When a sample was alloyed, the current density and time had to be increased as the amounts of alloying additions increased. Also, the effects of work hardening or surface grinding necessitated a change in coating conditions to cbtain a satisfactory coating.
.!-> g Na^O^ =>g NaH JPO4* H^O •»U0v> il^O
White; fairly hard coat
Sparkling gray; durable coat
Gray green; fairly hard coat
57^ NaCl03 $75,. H^O
*00g NajCO 5- 10H_>O S00.J H -6
Thin gray; fairly adherent coat
100.^ NaCIO 5
I hiii, ve ry hard green coat
1-^M NH4OH \-o : H :Q 10: N'H.)H_.P04
Desc ription of Coating
C urrent Density,
•17 5g uh
900 ml/l 1-1 HNO3 + H20 100 g/l NH4F-HF 100 ml/1 H2SiF6
From a commercial standpoint, the advantages of coating by chemical reaction are obvious. A detailed study was made to find baths which would coat titanium by simple immersion. The most promising of the baths developed are shown in Table Z. Of these, there are two compositions that furnish useful immersion coatings on titanium. They are (1) a fluoridephosphate bath and (I) a fluoride-borate bath.
ANODIC-COA'l ING BATHS
N 5 T • T u T E
immersion-coating procedure consisted of: (1) (2) (5) ( 1) (5) (6)
Bath No. 1
Coating Time, minutes 10
Desc ription of Coating
50g/l Na3P04-12H20 20g/l KF-2H20 11. 5ml/l HF solution*1)
5.1-5.2 Light silver gray; durable coating
50g/l Na3P04- I2H2O 50g/l KF-2H20 26ml/l HF solution*1)
40g/l Na2B407' IOH2O 18g/l KF»2H20 16g/l HF solution*1)
30g/l Na2C204 20g/l KF-2H20 lml/l HF solution*1)
Dark-gray coating (not repro ducible)
75g/l K2C204-H20 25g/lKF'2H20 3ml/l HF solution^ '
Light-gray coating (not reproducible)
> 1. 0
Dark, metallic gray; adherent coating
6. 3-6. 6 Metallic gray; adherent coat
3 3 3 3 3 3 3 3
The coating obtained from the high-temperature, fluoride-phosphate bath (No. 1, Table 2) on Ti-75, RC-55, and Ti-130B was light silver gray in appearance and possessed good adhesion to the base metal. No satisfactory coating was obtained on Ti-130A or 150A. The coatings have a composition of approximately 39 per cent fluoride, 3 per cent phosphate, .!-i per i-wrt potassium, and 17 per cent titanium, indicating the formation id ,i [uitubMum-titanium fluoride complex. ['he two must important variables of bath operation were temperature ann prll. Several common methods of pH control were tried and were found to oe unsatisfactory for use in a bath containing dissolved titanium and the active flimr-ide ion. A spectrophotometrie method proved to be the best way to maintain a. curate pH control of this bath. The thickness of the coating o.u t.M-
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