Washington Post reporters Scott Armstrong and Maxine Cheshire were named winners today of the "distinguished service in journalism" award for Washington correspondents by Sigma Delta Chi, the society of professional journalists.

Armstrong and Cheshire were among winners in 15 categories of print and broadcast journalism in the society's 45th annual awards competition. The awards annouced today were for outstanding performance in 1976. The winners were picked from a total of 1,207 entries.

The two Post reporters "triggered major repercussions in both diplomatic and congressional circles with their stories of heavy-handed efforts by South Korea to buy influence in Washington," contest judges noted.

"Their well-researched revelations of how congressmen and other U.S. officials accepted millions of dollars in personal and campaign gifts focused foreign power and a shocking lack of ethical standards on Capitol Hill."

Armstrong, 31, joined the Washington Post's metropolitan staff last yesterday after previous experience as a government investigator for the Senate Watergate Committee, private investigator, correctional program administrator, system analyst and automobile salesman. He received a bachelor's degree from Yale University.

Cheshire, 46, joined the Washington Post as a reporter in 1954 and became a columnist in 1965. Winner of three other awards in 1975, she was born in Harlan, Ky., attended the University of Kentucky and Union College in Barbodrville, Ky., and worked for the Knoxville (Tenn.) News frrom 1951 to 1954.

Winners in other categories include:

Newspapers: general reporting, George H. Reasons and Mike Goodman of the Los Angeles Times: editorial writing, George W. Wilson of the Phiadelphia inquirer; foreign correspondence, Joe Rigert of the Minneapois Tribune; news photography, Bruce Fritz of the Capital Times in Madison, Wis.; editorial cartooning, Paul Szep of the Boston Globe; public service. The Wall Street Journal.

Magazines: reporting Larry DuBois and Laurence Gonzales of Playboy magazine; public service, Philadelphia Magazine.

Radio: reporting, Mike Lee and Doug Tunnell, CBS News; public service, WCAU-AM Radionews, philadelphia; editorializing, Ed Hinshaw, WTMJ, Milwaukee.

Television: reporting KMJ-TV, Fresno, Calif.; public service, KNXT-TV, Los Angeles; editorializing. WCVB-TV, Needham, Mass.

Winners receive bronze medallions and plaques.