Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C19/00—Alloys based on nickel or cobalt
  • C22C19/03—Alloys based on nickel or cobalt based on nickel
  • C22C19/05—Alloys based on nickel or cobalt based on nickel with chromium
  • C22C19/058—Alloys based on nickel or cobalt based on nickel with chromium without Mo and W
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
  • F02B3/00—Engines characterised by air compression and subsequent fuel addition
  • F02B3/06—Engines characterised by air compression and subsequent fuel addition with compression ignition

Definitions

• the present invention is concerned with components of diesel exhaust systems particularly of diesel exhaust systems in large marine diesel engines.
• the exhaust system of a marine diesel engine should comprise components which are resistant to the products of combustion in a marine atmosphere of a representative grade of fuel likely to be encountered.
• the prior art has not solved the problem of providing such components in a satisfactory manner.
• marine atmosphere means atmospheric air which contains aerosol size or larger particles of sea salt generally produced by the action of wind on the crests of ocean waves. Wind tears at the crest of ocean waves dislodging particles of water containing sea salt. Some of these particles fall back into the ocean as spray while others tend to remain in suspension in the air either as liquid or as solid particles of dried out (or semi-dried out) solid.
• marine atmospheres contain not only high amounts of water vapor, but also significant amounts of sodium, potassium and other metals principally in the form of chlorides. For all practical purposes, a marine diesel engine is continuously burning fuel with air which contains these metals.
• the present invention contemplates components of the exhaust systems of marine diesel engines particularly exhaust valves having at least exhaust contacting surfaces made of an alloy comprising 0.02-0.07% carbon, 24-32% chromium, 0.7-3.0% titanium, 0.7-1.5% aluminum, 0.7-1.5% niobium, 0 to 0.1% zirconium, 0-0.006% boron, 0-1% iron, balance essentially nickel, together with conventional amounts of incidental and impurity elements. More specifically, entire exhaust components of marine diesel engines are made of the alloy of the present invention which can be in cast/­wrought form or can be made by powder metallurgical or other methods.
• the alloy can be heat treated by age-hardening in the range of about 675°C to about 725°C for about 2 to about 48 hours preferably after solution treatment at a temperature in excess of about 1000°C.
• age-hardening can be accomplished by slow cooling through the age-hardening temperature range or by use of two or more steps where the alloy is held at each step for a particular temperature and a particular length of time.
• iron should not exceed that amount which may be introduced inadvertently by use of scrap in preparing a melting charge or otherwise.
• the corrosion rate of alloys similar to those of the invention but containing in excess of 1% iron is significantly increased compared to that of alloys of the invention when tested at temperatures in excess of about 700°C in contact with synthetic ash containing vanadium in oxide form.
• Residual fuel ash deposits resulting from combustion of diesel fuel as described in Table II generally have compositions as set forth in weight percent in Table IV.
• Example 1 Five casts of Example 1 and four casts of Example 2 were made having average compositions in percent by weight as set forth in Table V. TABLE V Element Example 1 Example 2 C 0.03 0.03 Al 1.32 0.77 Cr 24.9 29.9 Nb 1.33 0.72 Ti 2.67 1.60 Zr 0.08 0.07 B 0.004 0.004 Ni Bal. Bal.
• the casts of the alloys of Example 1 and Example 2 were forged to bar stock and made into marine diesel exhaust valves. The alloys were heat treated for 2 hours at 1080°C followed by air cooling and, subsequently were aged for 16 hours at 700°C followed by air cooling.
• valves were tested in actual marine engine usage using residual fuel SSF7 with a sulfur content of 3.6% max., a vanadium content of 380 ppm max., an aluminum content of 3 ppm max. and a maximum ash of 0.1% (all by weight) and found to be very satisfactory. The tests of these valves gave full indication of practical utility in marine diesel engine service.
• Table VII shows that the tensile properties of the alloys of Examples 1 and 2 (especially Example 1) are more than adequate for use as marine diesel engine exhaust valves as compared to the tensile properties of prior art Alloy A.
• the tensile properties of the laboratory heats of Examples 1 and 2 reasonably matched the tensile properties of the comparable heats used to make exhaust valves when tested at room temperature and 550°C.
• the dynamic Young's moduli of 19 mm, forged bar samples of alloys of Examples 1 and 2 heat treated as specified hereinbefore were in units of N/mm2 x 103, about 217.7 at room temperature and decreased to about 182.7 at 600°C. These values are significantly higher than the dynamic Young's moduli of Alloy A at these temperatures. Mean coefficients of thermal expansion from 20°C to temperatures as high as 600°C for alloys of Examples 1 and 2 were marginally lower than such coefficients of thermal expansion for Alloy A.
• Table VIII sets forth data concerning relative corrosion of samples of Alloy A and the alloys of Examples 1 and 2 under laboratory conditions in contact with air and synthetic ash (as defined hereinbefore) when tested at 650°C for 500 hours with the air containing 0.2% sulfur oxide as the dioxide or trioxide.
• the alloys of the invention must contain less than about 1% iron in order to exhibit the excellent corrosion resistance as indicated in Table VIII at temperatures in excess of 700°C.
• alloys of the present invention are particularly useful as exhaust valves and parts, e.g. facings, coatings, external portion of composite exhaust valves and other exhaust contacting items for marine diesel engines and other diesel engines employing non-distillate diesel fuel, particularly such fuel contaminated with vanadium. It is to be noted that while alloys of the invention are contemplated to contain from 24 to 32% chromium, best results are obtained with alloys containing 24-28% chromium as is evident by the relatively better tensile characteristics disclosed in Table VII for the alloy of Example 1 compared to the alloy of Example 2.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Heat Treatment Of Steel (AREA)
• Exhaust Silencers (AREA)

Applications Claiming Priority (2)

Publications (1)

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Cited By (3)

Citations (4)

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• 1989
  • 1989-10-02 GB GB898922161A patent/GB8922161D0/en active Pending
• 1990
  • 1990-09-28 JP JP26036490A patent/JPH03120328A/ja active Pending
  • 1990-09-28 CA CA 2026551 patent/CA2026551A1/fr not_active Abandoned
  • 1990-10-01 EP EP90310724A patent/EP0421705A1/fr not_active Withdrawn

Patent Citations (4)

Non-Patent Citations (1)

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